Talk:Heat

Undo (2)

I am about to undo the latest revision by someone with the title 'Chjoaygame'. This editor has no user page and hase made no attempt to justify his edit, thus it close to vandalism. Chjoaygame, get yourself a user page and accept that some kind of consensus i.e. a little discussion is the norm for Wiki articles. --Damorbel (talk) 05:59, 27 September 2012 (UTC)

There is no requirement for a user to have a user page. Users are judged by their contributions, not the size of their ego user page. HumphreyW (talk) 06:57, 27 September 2012 (UTC)

article and sources refer to closed systems

Transfer of energy as heat is customarily discussed in physics texts by reference to closed systems or bodies. An example from the present article is

Mechanisms of heat transfer

Referring to conduction, Partington writes: "If a hot body is brought in conducting contact with a cold body, the temperature of the hot body falls and that of the cold body rises, and it is said that a quantity of heat has passed from the hot body to the cold body."

Referring to radiation, Maxwell writes: "In Radiation, the hotter body loses heat, and the colder body receives heat by means of a process occurring in some intervening medium which does not itself thereby become hot."

The article makes no attempt to consider transfer of energy as heat between open systems, in particular when diffusion is allowed between them.

The writing in the article should reflect this.Chjoaygame (talk) 07:16, 27 September 2012 (UTC)

Chjoaygame, you write "The article makes no attempt to consider transfer of energy as heat between open systems" Why? The article is about heat, the energy of vibrating particles, not the transfer of that energy between regions with different temperatures. --Damorbel (talk) 09:37, 27 September 2012 (UTC)

Damorbel, your comments do not address what is relevant here. What is relevant here is my edit which you undid.

Your comment (1) is a question to me as to why the article does not attempt to consider transfer of energy as heat between open systems. This may be a reasonable question, but does not impinge on my edit, which was making more explicit that the article as it stands is about closed systems or bodies. If you want to discuss the absence of something in the article about open systems, in particular when diffusion is allowed between them, this section right here is not the place for you to do so.

Your comment (2) is a complaint from you that the article ought to be about your idea that heat is the energy of vibrating particles, not, as it is, about the transfer of energy between bodies as heat. If you want to persuade editors to change the whole drift of the article, you may perhaps try to do so, but that is not directly relevant to my edit, which was making more explicit the present content of the article. I think, if you do try to persuade editors to change the whole drift of the article, you will encounter practically insurmountable opposition, because your idea that heat is the energy of vibrating particles is not a well defined one in physics. Thermodynamics has found that the ideas of internal energy and of entropy are appropriate instead. The ideas of internal energy and of entropy are fundamental to thermodynamics, essential to its proper understanding, and thoroughly supersede your ill defined idea of heat as the energy of vibrating particles.

Thus your above comments are not relevant as discussion about my edit, and indeed show that your undoing of my edit was unjustified and inappropriate.Chjoaygame (talk) 08:32, 28 September 2012 (UTC)

From what you write above (...your idea that heat is the energy of vibrating particles...) I understand your argument to be that heat is not the energy of vibrating particles, OK?

In that case would you care to explain what you accept as the proper name for the kinetic energy in vibrating or colliding particles?

This is not a trivial question because it is some of this kinetic energy that is transferred between material at different temperatures. It is entirely necessary that this energy is preserved, in one form or another, during and after the transfer; were this not so the 1st law of thermodynamics would not be valid. --Damorbel (talk) 18:31, 28 September 2012 (UTC)

Darmorbel, your comments continue to be irrelevant to the question at hand, which is about my edit. My edit is not about the questions you raise in your comments, however important and interesting they might be for some other context. My edit was making clearer and more explicit some of the points already in the article. From your comments, it continues to be evident that you have no justification for your undoing of my edit.Chjoaygame (talk) 01:20, 29 September 2012 (UTC)

Your edit is It is irrelevant to an article on heat because it woud only appliy to an article based on the 2nd law e.g. heat transfer. A proper explanation of heat has to be based on the energy contained in the motion of particles, not on the transfer of that energy between particles. It is quite possible to use examples energy transfer (diffusion collision, radiation etc.) to illustrate the fundamental definition of 'heat as the motion of particles' provided the relevance of the illustration is made clear and not used as some kind of substitute definition.

Your edit was reversed because it made no effort to clarify the distinction between heat and heat transfer, a major shortcoming in the whole article. --Damorbel (talk) 06:38, 29 September 2012 (UTC)

Dear Damorbel, you write: "Your edit was reversed because it made no effort to clarify the distinction between heat and heat transfer, a major shortcoming in the whole article." Your demand, that an edit should make an effort to clarify the distinction between heat and heat transfer, is a wish of yours but not in general a reasonable demand on an edit of this article. That you add "a major shortcoming in the whole article" shows that your wish in this matter is more or less contrary to the consensus on which the article is currently built. Thus your reason just stated for your undoing of my edit is not a valid or reasonable one.

Your claim, that my edit is "about whether heat transfer should be described as taking place between systems or bodies", shows that you did not carefully read or understand my edit, which is a defect of your reading, not of my edit. My edit was making it clear that the article is about closed systems or bodies, in contrast to being about open systems, as is clear even from what you write above: "It is quite possible to use examples energy transfer (diffusion collision, radiation etc.) to illustrate the fundamental definition ..."

Your claim that my edit "woud only appliy to an article based on the 2nd law e.g. heat transfer" is muddled. The present article does accept the second law as part of its basis, and so your suggestion that my edit does not apply because the present article is not based on the second law is mistaken.

Your gratuitous suggestions, that "A proper explanation of heat has to be based on the energy contained in the motion of particles, not on the transfer of that energy between particles. It is quite possible to use examples energy transfer (diffusion collision, radiation etc.) to illustrate the fundamental definition of 'heat as the motion of particles' provided the relevance of the illustration is made clear and not used as some kind of substitute definition", may or may not be reasonable. But they are not relevant to your undoing of my edit. My edit is making clear that the article as it stands refers to closed systems or bodies as distinct from open systems.

Thus your comments are an expression of your many times repeatedly expressed wish to radically change the whole drift of the article as it stands at present, and may or may not be reasonable in some other context. But, for the present question, they are mistaken or irrelevant and do not provide any justification of your undoing of my edit.Chjoaygame (talk) 08:28, 29 September 2012 (UTC)

Definition of Heat

The problem is that the definition of heat in the article is inconsistent in that it does not distinguish between heat and the transfer of heat. To assist in clarifying this I asked a question - would you .... explain what you accept as the proper name for the kinetic energy in vibrating or colliding particles?. This would help to clear up contradictions in the article. --Damorbel (talk) 09:50, 29 September 2012 (UTC)

Indeed the definition of heat in the article does not distinguish between heat and the transfer of heat. Indeed, the article explicitly says ″In physics, "heat" is by definition a transfer of energy and is always associated with a process of some kind. "Heat" is used interchangeably with "heat flow" and "heat transfer".″ I think editors who watch this page know well enough that you do not like that definition and interchangeable usage, from your many times repeated comments to that effect.

I do not see a good reason why I should try to comply with your gratuitous request that I "explain what [I] accept as the proper name for the kinetic energy in vibrating or colliding particles", to use your words. I can say that your phrase does not give a good definition of heat in physics. In order to understand why this is so and to understand a sound physical definition of heat, one needs to have a fair understanding of thermodynamics, more than is likely to be expressed both adequately for your needs and briefly in this talk page. Your view that this article contains "contradictions" is due to your non-acceptance of the definition of heat that has been reached by consensus for this article.Chjoaygame (talk) 10:38, 29 September 2012 (UTC)

My question is simple, where in the article is the difference between heat (particle vibrations) and heat transfer? The matter is not difficult, particles at a high temperature vibrate with a geater energy than those at a lower temperature; when two (or more) samples matter with different temperature come into thermal contact (by whatever means) energy is transferred from the high temperature to the lower.

After a time the temperatures will equalise, which means that the vibrational energy of the particles is the same and heat transfer stops.

At present the article gives the impression that "heat has stopped" when the temperatures are equal; this can't be true because the particles are still vibrating with a common energy i.e. with a common temperature, even though the heating of the cooler body by the hotter has indeed come to a stop. --Damorbel (talk) 11:18, 29 September 2012 (UTC)

Dear Damorbel, you ask "where in the article is the difference between heat (particle vibrations) and heat transfer?" It seems to you that your question is simple, but in reality it is muddle-headedly posed, and so has no useful answer. Your muddle is of your own making. You find the article hard to understand because you insist on your own muddled approach to heat. By misdirecting your efforts to trying to force that muddled approach onto others, you distract yourself from getting a better understanding. You muddle yourself about a thermodynamic matter by prematurely dabbling in the kinetic theory that provides a microscopic explanation for it. Instead of that, if you spent some time trying to follow the approach of basic thermodynamics itself, you would find that things would become clearer to you.Chjoaygame (talk) 14:36, 29 September 2012 (UTC)

Chjoaygame, the article would be considerably improved if it contained a clear distinction between heat (energy - joules), heat transfer (power - watts or joules/second) and the role that temperature (joules/particle) plays in both. --Damorbel (talk) 06:03, 1 October 2012 (UTC)

Damorbel, you continue to express your view that "the article would be considerably improved if it contained a clear distinction between heat (energy - joules), heat transfer (power - watts or joules/second)..."

The article is based on a view different from yours, but found almost universally in reliable sources on thermodynamics, and accepted by the consensus on which the present article is based. It is that the idea of heat in thermodynamics refers to a quantity of energy transferred in a process. It is fundamental to thermodynamics that heat is a process quantity, not a state quantity. For a discrete process that carries an initial state of a closed system to a final state, with finitely separated initial and final states of thermodynamic equilibrium, the heat transferred is a quantity of energy. For a continuous-time process of a closed system, one can consider the rate of heat transfer as a power, energy transferred per unit time, provided a temperature exists throughout the process and provided some other conditions are satisfied. There is in thermodynamics no "state quantity of heat". The energy status of a closed system or body is described in thermodynamics by its internal energy. It is the message of the first law of thermodynamics that the internal energy is a state variable, and that it cannot in thermodynamics unconstrainedly be split into moieties which are also state variables. The notion of unconstrained splitting refers to the fact that different amounts of heat can be extracted from a body depending on the constraints under which the heat is to be extracted.

The reason for this is that energy of a body which might be available for extraction as heat, microscopically considered, is partly in the internal kinetic energy and partly in the mutual internal potential energy of the constituents of the body, and that the distinction between these two factors cannot be made without constraint for the process of extraction. This is another way of saying that the heat transferred in a process of a closed system is a function of the path of the process; the path of the process is specified in terms of constraints on it.

To judge from what you write, it seems clear that you do not accept the thermodynamic view that I have expressed just above, that is the basis of the present article.Chjoaygame (talk) 07:46, 1 October 2012 (UTC)

Chjoaygame, the concept of heat as the vibrational (kinetic) energy of fundamental particles is well established by kinetic theory, the heat article needs to recognise this, at present it doesn't, e.g. when it has "[Heat is not regarded as being stored within a system]"

Up until now nothing you have written explains what name or function the article should give to the energy stored in the motions of particles. I would be much more inclined to agree with you if you could sort this this out. --Damorbel (talk) 09:22, 1 October 2012 (UTC)

Damorbel, you are insisting on your own personal viewpoint that is fundamentally contrary to the viewpoint taken by the article as it stands, which is the result of consensus of editors based on reliable sources. Your personal viewpoint is a very personal and private reading of the sources. You insist on giving conceptual priority to your reading in terms of "kinetic theory", contrary to the general principle that the thermodynamics of heat is about macroscopic measurements made on closed systems. While you insist on this personal and private reading, you will not be able to understand the consensus viewpoint in terms of thermodynamics, which is that of this article as it stands. Your personal viewpoint is muddled and inconsistent, though you are blind to its defects. The thermodynamic concept that you need to understand is called 'internal energy'. Microscopically it is explained by the internal kinetic energy and the internal mutual potential energy of the constituents of the system. The great discovery of Clausius was that macroscopically for thermodynamics the internal energy is a state variable that cannot be "sorted out" (as you wish) into parts so as to produce part that would be an unconstrained quantity of heat that would be a further state variable. The internal energy discovered, but not named, by Clausius was not recognized by him at first as a quantity of energy; it took him 15 years to come to understand that it was such. Your notion of "the energy stored in the motions of particles" is not a well defined quantity; however much you might wish it to be recognized as a physical quantity, it is just wishful thinking without physical understanding. In chasing "the energy stored in the motions of particles" you are chasing a will-o'-the-wisp invented by you in your own internal word games, without physical understanding. It is possible that you are not to blame for your misunderstanding, but were led to it by would-be self-judged "clever" teachers who thought that they could teach kinetic theory without a prior basis of thermodynamics; this was a regrettable fashion in teaching at one stage.

In order to understand the thermodynamics of heat, you need to abandon your present personal and private viewpoint in this, because it blocks your understanding of the thermodynamical viewpoint. No progress will occur until you grasp this nettle.Chjoaygame (talk) 11:09, 1 October 2012 (UTC)

Chjoaygame, you write (above) "the energy stored in the motions of particles" is not a well defined quantity", I understand from this that you do not accept that this energy is a function of the temperature of the particles i.e E = 1/2m/v² = 1/2k_BT?

You seem to find Clausius slow "The internal energy discovered, ... by Clausius was not recognized .... as a quantity of energy; it took him 15 years to come to understand ...". Is his slowness important to your argument?

So when Clausius wrote an article “On the Nature of the Motion which we call Heat” (Über die Art der Bewegung die wir Wärme nennen - available in English from Google Books) was he wrong?

Clausius writes (on p127, after equ.(9)) "No constant need be added, since, as before remarked, the heat in the gas is proportional to the vis viva [energy] of the translatory motion, and hence to the absolute temperature" --Damorbel (talk) 12:39, 1 October 2012 (UTC)

As I already mentioned several times, while you insist on your personal reading of the matter, you will not be able to understand the thermodynamics of heat. You are now trying to distract attention from thermodynamics by arguing in terms of Clausius' understanding in terms of kinetic theory. You may feel that this is a clever debating move, and indeed it looks good. But it doesn't cut it, because the argument that Clausius is using does not take into account the internal mutual potential energy of the constituents of the body. So, yes, I am saying that Clausius' argument here, on which you rely, is wrong if taken as a general argument for the thermodynamic nature of heat. As I mentioned, Clausius' discovery of internal energy was not at first fully recognized for what it was even by Clausius. The reason I mentioned it was to soften the blow for you when you are eventually struck by the weight of the concept of internal energy, which reduces to nonsense your wishful thinking about heat as a state variable. You are not the only person to have difficulty grasping the concept of internal energy. The article by Clausius that you cite was written in 1857, some years before 1865 when he accepted the understanding of his quantity U as internal energy. Your relying on Clausius' 1857 article for your case shows that you will go to any length to hold to your personal and private reading of heat, so as to avoid your gaining an understanding of heat in terms of changes in the internal energy of a closed system, as held by thermodynamics. There are none so blind as those who will not see.

It struck me that perhaps an analogy may help you. Perhaps not; perhaps you will just use it as another distractor to help you hold to your personal view and protect you from physical understanding which you are so strenuously avoiding. The analogy likens the internal energy of a body to the water in a pond. The pond is filled from a stream and emptied by a pump. It also receives water from the rain and from snow and dew. It also evaporates. The analogy likens the stream and the pump to "work" and it likens the rain, dew, snow, and evaporation to "heat". It is not possible by ordinary macroscopic measurements to split the water in the pond into "work" water and "heat" water. You would like to make such a split, but it won't happen.

Dear Damorbel, you are a master of distraction and irrelevant rhetoric, but you are no good at sound reasoning about the physics of heat. I have mentioned before that you are challenged in the logic department. In this case, it seems to me that you are perhaps making the logical error of taking ordinary language as if it had the compositional property that mathematical formulations mostly have. Compositionality means that the meaning of a clause can be determined simply by considering it as a composition of units each of which separately has its respective fixed and definite meaning. That is to say, you are thinking that because one speaks of extracting heat from a body, it follows that it makes sense to think of the body as storing heat. The ordinary language construction makes that look plausible, on the assumption of compositionality, but it is nevertheless wrong in logic, because ordinary speech does not have the compositional property.

You have indeed this time till now succeeded in luring me into trying to have a rational conversation with you, an error which I have previously recognized as an exercise in futility. You are afresh showing your ability to avoid real understanding by admittedly clever rhetoric. I have had a good try at helping you here, perhaps foolishly, given your present characteristics. While I congratulate on so far luring me into a futile exchange, I don't want to continue with it. You are showing every sign that you are unable to bring yourself to attend to reason in this matter, and are hardly likely to change in that respect in this conversation. You can lead a horse to water, but you can't make it drink.Chjoaygame (talk) 15:47, 1 October 2012 (UTC)

Perhaps it may be useful to Damorbel to read exactly why the Clausius 1857 paper does not support Damorbel's view of things as he supposes it does. Clausius had at that time, in 1857, not yet come to call his state function U the internal energy. In that paper he still spoke of the "generation and consumption of heat" and used the concept of "interior work". That 1857 use of the word heat by Clausius is not that of present day thermodynamics; in many cases Clausius spoke of "heat" when today we would speak of internal energy, but it was not not till 1865, some years after the 1857 paper to which Damorbel refers, that Clausius started using the term energy for his state function U which we now call internal energy. "Interior work" corresponds to what we might today call the internal mutual potential energy of the constituents of the material. For gases, this is usually not as great as the kinetic energy of the molecules, but for liquids and solids it is usually greater. Damorbel wants us to forget about the internal mutual potential energy of the constituents of the material, and so he thinks mostly, it seems, in terms of ideal gases, which behave somewhat differently from real gases and very differently from solids. For ideal gases one can indeed forget the internal mutual potential energy of the molecules. But the thermodynamic concept of quantity of heat tranferred is intended to deal not only with ideal gases but also with real gases, liquids, and solids. So it takes into account not only the kinetic energy that Damorbel thinks about, but also the potential energy that he doesn't think about. Damorbel makes the basic error of building his conception of heat from the kinetic theory of gases, instead of the simpler and more general theory of macroscopic thermodynamics, which is needed to get a full understanding of the nature of heat. Damorbel is not the only person to make this mistake, and often those who make it think they are very clever, and are being more "fundamental". The result is that Damorbel, and sometimes others, get a muddled view of the nature of heat.Chjoaygame (talk) 20:11, 2 October 2012 (UTC)

Chjoaygame, internal energy, U has two components kinetic energy (Q) which is 'heat' and potential energy which has many different forms, chemical bonds, van der Waals forces etc. Potential energy is completely separate from kinetic energy because it, by definition, is about static forces, i.e. it does not involve particle motion; for that reason potential energy is irrelevant to the definition of heat. --Damorbel (talk) 07:30, 3 October 2012 (UTC)

Damorbel, now you have put your cards on the table. Thermodynamics is largely interesting because its definition of quantity of heat transferred is sensitive to internal mutual potential energy, which you say here is irrelevant to your definition of heat. In direct conflict with your view, in thermodynamics, internal energy U cannot be unconstrainedly split into two components, one of which would be a state variable that might attract your private label Q. This puts you thoroughly in direct conflict with the thermodynamic analysis. You can cite the name of Clausius as a specious rhetorical move, but you have missed understanding the main point of his discovery of U. You will remain beyond help until you try to see your mistake here.Chjoaygame (talk) 08:38, 3 October 2012 (UTC)

Chjoaygame, you do not mention temperature. According to Clausius heat (vis viva; energy in modern terms) in a given substance, is proportional to absolute temperature. The energy in different substances at the same temperature is not the same because not all substances have the same specific heat because different substances have differing numbers of (kinetic) DOF (degrees of freedom). Non-kinetic e.g. potential energy, degrees of freedom, have a variable effect on internal energy e.g. zero for a perfect gas, (3 DOF) (there is no potential energy in a (theoretically) perfect gas). Real gases have intermolecular (van der Waals) forces that make them change state (liquify, solidify etc.) at various temperatures. --Damorbel (talk) 09:13, 3 October 2012 (UTC)

In thermodynamics, temperature is related to heat transfer between bodies or closed systems. When two bodies with different temperatures are in contact through a connection permeable only to heat (as noted by Carathéodory), then heat is spontanteously conducted from the one with the higher to the one with the lower temperature. In physical reality, there is no immediate and simple one-to-one relation between the temperature of a body and its internal energy. In examination of the microscopic mechanisms of energy, one finds various indirect and complicated relations between the temperature of a real body and its internal energy. Only in a merely idealized explanation, such as of an ideal gas, does one find more direct and simple relations between the temperature of a body and its internal energy. Yet you are demanding that such merely idealized cases expressed by idealized microscopic models should define your term "heat in a body", as if it were a state variable. The point of the thermodynamic analysis of heat is (without consideration of the microscopic models, which are in general beyond the feasible practical reach of precise calculation) to deal with the non-idealities which you wish to ignore when you engage in wishful thinking in terms of your idealized examples. Your approach ignores and effectively contradicts that of thermodynamics. And you are trying to force its acceptance as a new basis for this article, contrary to the (admittedly not quite unanimous) consensus of editors, and contrary to the weight of reliable current sources.Chjoaygame (talk) 11:53, 3 October 2012 (UTC)

"temperature is related to heat transfer" How? For transfer of energy? For energy to be transferred there needs to two temperatures, the heat source (T₁) and the heat sink (T₂). Which of the two do you have with a fever of 98.4^oF? --Damorbel (talk) 13:47, 3 October 2012 (UTC)

Chjoaygame, what does temperature measure? --Damorbel (talk) 13:50, 3 October 2012 (UTC)

With a temperature of 98.4°F, you don't have a fever.

Temperature measures the partial derivative of internal energy with respect to entropy at constant volume and chemical constitution.Chjoaygame (talk) 13:09, 4 October 2012 (UTC)Chjoaygame (talk) 23:02, 5 October 2012 (UTC)

Chjoaygame, temperature is the energy per particle, as with the Boltzmann constant. Temperature can only be defined at maximum entropy (Thermal equilibrium), or don't you agree. BTW(1), the thermal equilibrium article describes the equilibrium state as existing with >1 temperature thus with entropy <Smax, I intend to correct this. BTW(2) since temperature can only be defined at Smax (dS/dt = 0) how can it be the partial derivative of internal energy with respect to entropy? --Damorbel (talk) 10:10, 5 October 2012 (UTC)

In order to find the answer to your question about the partial derivative, you will need to study thermodynamics.Chjoaygame (talk) 13:59, 5 October 2012 (UTC)

who is the author of the article? note to the editor who asked that question

There is no well defined 'author of the article'. The Wikipedia works by people like you adding or subtracting bits and pieces. You were a part-author till you removed your edit.Chjoaygame (talk) 17:21, 1 October 2012 (UTC)

What is this about? --Damorbel (talk) 20:33, 1 October 2012 (UTC)

The question was put in the article with this edit and then removed again. — HHHIPPO 20:58, 1 October 2012 (UTC)

This was simple vandalism, no need to raise it in the talk pages, there is quite enough wrong with the article already! --Damorbel (talk) 06:40, 3 October 2012 (UTC) heat is awesome — Preceding unsigned comment added by 68.177.37.202 (talk) 14:30, 10 October 2012 (UTC)

new section on usage of words

I am putting in a new section on the usage of words. Previously, a section on 'Semantics' was deleted for no clearly stated reason. There continue to be issues about the meaning of the word heat, and my current new section tries to deal with some aspects of these issues. My new section adheres strictly to the current consensus of editors of this article, but the consensus in not unanmimous. The consensus accepts the weight of opinion in present-day reliable sources.

Dissenting editors who reject this consensus like to think of heat as something that can be "stored" in a body, or like to speak of "thermal energy" as if it were a state variable, as a "part" of the internal energy. In terms of present-day physics, this dissent is irrational. I do not know how to deal happily with this dissenting rejection of the weight of opinion in present-day reliable sources. To try to make it a major part of the present article would make a hardly comprehensible mess of it, without much compensating benefit other than appeasing irrational dissent. Therefore I am just trying to state the consensus view here.Chjoaygame (talk) 06:15, 3 October 2012 (UTC)

Perhaps I should add that the present article contains inconsistencies when considered from the consensus viewpoint. Gradually we may perhaps remedy the inconsistencies.Chjoaygame (talk) 06:19, 3 October 2012 (UTC)

Chjoaygame, please check your links, the one you give does not refer to 'semantics'. --Damorbel (talk) 06:43, 3 October 2012 (UTC)

"My new section"? I'll accept 'My new edit' but nothing about the article belongs to you. --Damorbel (talk) 06:46, 3 October 2012 (UTC)

"Usage of words"

I have undone this major new section because it represents the view of one editor only, there has been do discussion of the content with other interested editors.--Damorbel (talk) 06:22, 3 October 2012 (UTC)

What is wrong with the 'undone' section:

1/ it had "heat is defined as a word that refers to....". Heat is defined as a word, only in the semantic sense.

2/ "But in strict physical terms". I think this should be 'physics'; 'physical' is not a science with 'terms', it's an adjective.

3/ "process is admitted as heating only when what is meant is transfer of energy as heat". I don't think so; surely heating is any process that causes the temperature to rise, just as cooling is any process that causes the temperature to fall; otherwise one is stuck with the concept of negative heat.

4/ "The heat transferred that leads to melting without temperature change is said to be 'latent'. How can this be true? The term latent heat was introduced by http://en.wikipedia.org/wiki/Joseph_Black#Latent_heat long before there was a satifactory definition of heat, a more accurate name would be potential energy with a clear indication as to what kind of potential energy (e.g.chemical etc.). As a scientific term latent heat is imprecise and the article should make this clear.

5/ "it would be physically improper to speak of 'heat production by friction". So friction does not give rise to heat?

6/"Occasionally a present-day author, especially when referring to history, writes of "adiabatic heating", though this is a contradiction in terms of present day physics". Adiabatic means 'without heat transfer'. It frequently refers to compression that raises (expansion - lowers) the temperature of a gas so quickly that there is no diffusion (or other transfer) of heat from outside the volume being considers i.e. the volume is insulated, adiabatic means no passage (of heat) - the opposite of diathermous

7/"nowadays one speaks of conversion of other forms of energy into internal energy." Only correct if you separate the energy arising from particle motion i.e. enegy that is proportional to temperature, only particle motion gives rise to temperature effects. --Damorbel (talk) 08:31, 3 October 2012 (UTC)

Now :William M Connolley has reversed my deletion without any attempt to contribute to the discussion. This puts the whole matter at the school playground level (T'is! - T'isn't!). I'm sorry about this, it makes a real mess of an article. Wikipedia is a great invention but this no discussion (= mindless) behaviour can only damage the Wiki project. --Damorbel (talk) 10:52, 3 October 2012 (UTC)

As I noted (immediately above) Wm. Connolley has reverted my deletion, making the coment "Undid revision 515749953 by Damorbel (talk) tahts a bit abrupt and not obviously necessary"

To me Wm. C. deleted this because it wasn't obvious to him. Fair enough, William; so it is not obvious to you despite the explanation above? I get from this you did not understand the purpose of the deletion, then why not discuss this on the talk pages? The article is a lot better when it is not discussing 'usage' in the way of the deleted material. Therefore, in view of no reason being presented for restoring the section, I am deleting it again. --Damorbel (talk) 12:52, 13 November 2012 (UTC)

Broadly all seven of these objections look wrong. And the section looks roughly correct although not perfect. It is far down the article and does not displace other more immediately useful stuff. So it should stay in. --BozMo talk 15:41, 13 November 2012 (UTC)

Nice of you to give an explanation BozMo "Broadly all seven of these objections look wrong" But don't you think your explanation is a bit thin? Lacking in substance perhaps? I mean is "Broadly all seven of these objections look wrong" adequate? Um only the super intelligent will be able to work out which of your 8 words are relevant to the detailed argument I presented above!

I am sorry I am struggling to find a detailed argument in your comments. Or an argument for that matter. I can see a number of assertions, all of which look broadly questionable or wrong. For example the expression "in strict physical terms" is widely used with the meaning given in the section since physical has a common meaning of "in terms of physics". Your proposal of "in strict physics terms" is an rare ungrammatical combination which as far as I can see is used only 74 times in the entire worldwide web. --BozMo talk 15:43, 14 November 2012 (UTC)

I suggest you improve your contribution or withdraw it. --Damorbel (talk) 15:55, 13 November 2012 (UTC)

a well-known editor is currently having an unchecked field day at the article on Thermal equilibrium

I think hardly anyone watches the article on Thermal equilibrium. Because of this, I think, a well-known editor is currently having an unchecked field day there.Chjoaygame (talk) 18:54, 9 October 2012 (UTC)

What about convection?

Convection, in itself is not conduction nor radiation... --201.204.200.18 (talk) 02:49, 13 November 2012 (UTC)

See http://en.wikipedia.org/wiki/Convective_heat_transfer --201.204.200.18 (talk) 02:52, 13 November 2012 (UTC)

Physics uses a technical definition of heat as energy in process of transfer by conduction or radiation. This is not the ordinary language usage, nor is it the loose usage that is found in natural science writings when the strict technical definition is not being attended to. As it happens, only for some special real world processes can the notion of heat conduction be uniquely defined, and for the general case, diffusion makes it impossible to define conduction uniquely. As a result, transfer of internal energy calls for an account that relies on the concept of entropy as well as on the concept of energy, as was worked out by Gibbs.

'Convection of heat' is a term that falls into the area of ordinary language or loose usage, and is not admitted by the strict technical physical definition of heat transfer. The strict technical physical definition requires that one should speak of 'convection of internal energy'.

The reason for this is that, in the thermodynamic conception, internal energy consists of microscopic mutual and internal potential and kinetic energies of the particles of the material of the body of interest. The split into kinetic and mutual and internal potential energy is not unique, but depends on the process contemplated for defining the split. Inextricably linked with this is that the internal energy of a body cannot be split uniquely into a work component and a heat component, because again the split depends on the process contemplated for defining the split. The outcome is that heat transfer can be uniquely defined only by specification of the path of the process of transfer. Thus heat transfer is essentially a process concept, while there is no unique definition of a state variable of heat content. In ordinary language, one might say that heat is not an enduring substance. For the same reasons, the phrase "thermal energy" is a loose usage but does not refer to a uniquely defined physical quantity. In ordinary language, thermal energy is not an enduring substance. In ordinary language, one might use a metaphor and say that heat and thermal energy are moveable feasts.

This presents a practical problem for the Wikipedia, because there needs to be some reconciliation between the ordinary language usage and the strict technical usage. The current consensus solution in the Wikipedia is to say explicitly and deliberately that the articles use not the ordinary language or the loose usages, but strictly follow the strict technical physical definition. There are some dissenting voices from this consensus. Mostly, dissenters seem to lack comprehension of the reasons for the strict technical definition, but they do not see themselves as lacking such comprehension.

I am not familiar with the engineering literature, but I have an impression that engineers sometimes or often follow the loose usage that confounds heat content with internal energy, in effect, in loose agreement with the ordinary language usage. So they speak of convection of heat. I think they also speak of "thermal energy" as if it were a well defined quantity. They are practical people.

As school children, we were taught that heat is transferred by conduction, radiation, and convection. As school children, we were not taught thermodynamics, and we did not learn of the concept of internal energy.

It would be devastatingly complicated and confusing to try to word the Wikipedia articles so as to express, alongside one another at every step, both the ordinary language and loose usages, and the strict technical physical definition.

Those who prefer the ordinary language usage will have native facility in translating the strict technical physical definition into ordinary language, but very few readers will have the skill to consistently translate from ordinary language to strict technical physical definition usage. The current Wikipedia editorial consensus undertakes to consistently supply and apply the results of such skill.Chjoaygame (talk) 06:57, 13 November 2012 (UTC)Chjoaygame (talk) 07:03, 13 November 2012 (UTC)

201.204.200.18, I would prefer to reply to a name, will you help?

Chjoaygame, yet another example of where you theory of 'heat' as 'transfer of energy' (which should be heat transfer) breaks down.

For example you write:-

"'Convection of heat' is a term that falls into the area of ordinary language or loose usage, and is not admitted by the strict technical physical definition of heat transfer. The strict technical physical definition requires that one should speak of 'convection of internal energy'."

Convection can only take place in a system not in equilibrium in a gravitational field (let us not get into discussion of forced convection which is related but has many complicating variables).

So what part of 'internal energy' is gravitation?

If you wish to examine the matter further I suggest you read the Wiki article on the Navier–Stokes equations.

As soon as you abandon the concept of heat as the kinetic energy in microscopic (i.e. indivdual particles) you will not find coherent explanations of thermal phenomena such as convection. --Damorbel (talk) 08:35, 13 November 2012 (UTC)

Statistical mechanics explains classical thermodynamics, it does not replace it. Classical thermodynamics makes no reference to the particulate nature of matter and is a theory that is complete. It uses measurements of e.g. specific heat, whereas statistical mechanics explains the results of those measurements in terms of a particulate theory of matter, but classical thermodynamics is not at a loss to predict the macroscopic results of an experiment couched in macroscopic variables. Einstein said "A theory is the more impressive the greater the simplicity of its premises, the more different kinds of things it relates, and the more extended its area of applicability. Therefore the deep impression that classical thermodynamics made upon me. It is the only physical theory of universal content which I am convinced will never be overthrown, within the framework of applicability of its basic concepts." He was NOT talking about statistical mechanics, he was talking about classical thermodynamics. The Navier-Stokes equations make no reference to particles nor particle velocities. They use only macroscopic variables (pressure, velocity, etc.) They and all of classical thermodynamics may be derived from statistical mechanics, but if ever a statistical mechanics theory disagrees with classical thermodynamics, then that statistical mechanics theory is wrong. Its fine to treat the two as a combined theory, bouncing back and forth between the two, when working on a particular problem, but when doing theoretical work, one should really maintain the distinction between the two. See the introduction to http://www.e-booksdirectory.com/details.php?ebook=4226 PAR (talk) 15:52, 13 November 2012 (UTC)

http://en.wikipedia.org/wiki/Rayleigh%E2%80%93B%C3%A9nard_convection --201.204.200.18 (talk) 20:42, 13 November 2012 (UTC)

http://books.google.co.cr/books?id=pJaiReRZvHMC&printsec=frontcover&dq=convection+fluid+flow&hl=es&sa=X&ei=17CiUMXzKYSu8ASP5YC4BA&ved=0CC0Q6AEwAQ#v=onepage&q=convection%20fluid%20flow&f=false --201.204.200.18 (talk) 20:47, 13 November 2012 (UTC)

PAR what do you mean when you write "Classical thermodynamics makes no reference to the particulate nature of matter"? What then does N (Avogadro's number) refer to in the gas laws? Or can you explain the meaning of Molar form without mentioning particles. Thermodynamics without particles, absurd! --Damorbel (talk) 21:36, 13 November 2012 (UTC)

Avogadro's number is not a part of classical thermodynamics. PV=Nkt is an equation of state expressed in statistical mechanics terms. In classical thermodynamics its PV=mRT/λ where R is a universal constant m is mass and λ is a constant which must be measured for each material. It was discovered that e.g. the λ of oxygen gas was very nearly 16 times that of hydrogen gas. The particulate theory of matter explains this by saying each molecule of oxygen is 16 times the mass of a molecule of hydrogen. Not exactly right says classical thermodynamics, but that's the particulate theory's problem, not classical thermodynamic's problem. Particulate theory has to improve by dealing with isotopes, etc. Classical thermodynamics is based on macroscopic measurements, it is a phenomenological theory, and it has always given the right answer, it doesn't deal with particles, and it doesn't have to. If the particulate theory falls short, that's not classical thermodynamic's problem. Don't get me wrong, I would not think of dealing with a problem in purely classical terms except to understand pure classical thermodynamics, but if you run into problems, its either because A) you don't understand classical thermodynamics or B) you don't understand particulate theory/statistical mechanics, or C) particulate theory/statistical mechanics is not up to snuff. (Fourth possibility - classical thermodynamics is wrong and you win the Nobel prize and become famous). See the explanation just below this. PAR (talk) 05:14, 14 November 2012 (UTC)

PAR you write:- "Avogadro's number is not a part of classical thermodynamics." Really? Then you write "PV=Nkt is an equation of state expressed in statistical mechanics terms." And you are maintaining this eliminates the role of particles? You then cite PV=mRT/λ as an example of thermodynamics without particles. What, then, do you think R is all about, where $\qquad R=N_{\rm {A}}k_{\rm {B}},\,$? That is to say: N_A = R/k_B. You make it worse by not recognising that your k (= k_B) is the Boltzmann constant, which is the energy per particle for each K (Kelvin) --Damorbel (talk) 09:26, 15 November 2012 (UTC)

Classical thermodynamics is actually known to be wrong, the statements it makes are only valid in a statistical sense. The second law as formulated in classical thermodynamics is false, the entropy of isolated systems can spontaneously decrease; this has been observed in experiments and the observations are consistent with the predictions of the fluctuation theorem.

One can still argue that thermodynamics is universal, many of the laws are independent of the microscopic model, so in this respect, statistical mechanics is not more fundamental. But then I would say that this occurs in most of physics. If you wouldn't have emergent laws at higher levels then we would not have made much progress in science. The laws of classical mechanics are is a sense universal, this allowed Newton to discover these laws without him having to figure out all the details of superstring theory first. Count Iblis (talk) 18:40, 14 November 2012 (UTC)

Count Iblis makes a fair point. As I interpret things, classical thermodynamics has a range of applicability, and it shouldn't be applied outside that range, because outside that range it isn't applicable. Within that range it has a degree of universality, which sometimes leads people to say that it is universal, punto. No, not universal punto, but "universal" only within a limited range of applicability. It takes some effort to remember to define that range.Chjoaygame (talk) 06:14, 15 November 2012 (UTC)

Count Iblis writes "Classical thermodynamics is actually known to be wrong,". Just what do refer to when you assert 'thermodynamics is known to be wrong'?

This statement, made without any support, is quite characteristic of the defects of the Heat article. Not having any support it is simply a wild assertion that occupies space without contributing anything. Count Iblis, your contribution is through and through useless; "statistical mechanics is not more fundamental", what does this mean? Can you measure degress fundamentalness? Please, will contibutors not contaminate talk pages with vague statements and remarks about the contributors instead of the contributions. --Damorbel (talk) 09:26, 15 November 2012 (UTC)

Actually the general laws of thermodynamics were developed with regard to the concept of system, not with regard tho the concept of particle. Statistical thermodynamics was a later concept that was developed in order to establish relationships between microscopic properties of particles and the general theory, but statistical thermodynamics is not fundamental to the general laws of thermodynamics: actually different forms of these laws apply in the definition of entropy as an aspect of information in information physics, per example. Statisical mechanics was started around 1870. Carnot published his works around 1824. Rankine published his textbook around 1850. Around 1850 Rankine, Lord Kelvin and Clausius established the first and second law of thermodynamics and most of the fundametal aspects of this science (before the concept of statistical thermodynamics related these concepts, in some aspects, to the microscopic properties of particles). When one studies the thermodynamics proposed by Gibbs one does not deal much into the aspects of how microscopic particles behave. It is true that Avogrado's proposition regarding the number of particles in a gas and it's volume dates from 1811, but it is not fundamental in defining the laws of thermodynamics as such. The value of the Avogadro's constant started to be established by 1865. When Milikan measured the charge of the electron in 1910 it was easier to establish the value of the constant. Perrin proposed the measure with regard to O2 in 1909. Gibbs work was published between 1875 and 1878. Clearly the general laws of thermodynamics were established without the contribution of statistical mechanics and without regard to the microscopic components of the system. They stem from abstract thought and experimentation and have been able to withhold the passage of time: even at the quantum level and the general theory of relativity level and the information theory and information physics theory they seeem to still apply, albeit with different formulations. But heat and heat transfer are not "thermodynamics", they relate to the emission of radiaton between 2 bodies at different temperatures, the conduction of heat when two bodies are in physical contact on a macroscopic scale, which relates to the "vibration" and "kinetic energy" of atoms, if I understand correctly, and, if I understand correctly, in fluids (whether it is plasma on the Sun, air on the atmosphere, etc.) by the convection (movement of larger masses of fluid). In fluids we have the problem that the equations we use to model the system (Navier-Stokes) are not mathematical proven to be exist and be smooth in a generalized form. This implies problems specially in turbulent flow (which is where convection is more important). Convection and fluid phenomena are studied in chemical engineering as "transport phenomena" where problems related to heat, mass and momentum transfer are dealt with in conjuction. (see: http://en.wikipedia.org/wiki/Transport_phenomena). "In engineering and physics, the study of transport phenomena concerns the exchange of mass, energy, and momentum between observed and studied systems. While it draws from fields as diverse as continuum mechanics and thermodynamics, it places a heavy emphasis on the commonalities between the topics covered. Mass, momentum, and heat transport all share a very similar mathematical framework, and the parallels between them are exploited in the study of transport phenomena to draw deep mathematical connections that often provide very useful tools in the analysis of one field that are directly derived from the others. Generally speaking there is a current ongoing philosophical debate about a theory of everything that should encompass all phenomena." --201.204.200.18 (talk) 22:15, 13 November 2012 (UTC)

Also see: http://en.wikipedia.org/wiki/Rayleigh_number --201.204.200.18 (talk) 01:09, 14 November 2012 (UTC)

Editor 201.204.200.18 and Editor PAR write well above, in close agreement about the fundamental distinction between thermodynamics proper and statistical mechanics. I think they represent the overwhelming consensus of Wikipedia editors on that, and in general I accept that consensus. There are some dissenting voices. It is not easy to see how to satisfy the dissenters.

Editor 201.204.200.18 writes of "a theory of everything that should encompass all phenomena". I think we are not there yet, and that we should not try to write as if we are nearly there.

Editor 201.204.200.18 writes: "But heat and heat transfer are not "thermodynamics"..." It is true the heat and work are not the fundamental concepts of Gibbs' presentation. Gibbs' thermodynamics is especially intended to deal with open systems, for which heat and work are in general not uniquely defined. But Gibbs does rely on the concept of absolute or thermodynamic temperature. This is determined by considering special cases, namely closed systems, for which heat and work transfers can be uniquely defined. In this sense, heat transfer is essential to thermodynamics.

Editor 201.204.200.18 cites some engineering writing that speaks of heat when a strict technical physical definition would speak of internal energy. This is a problem for us here. May I repeat what I wrote above:

It would be devastatingly complicated and confusing to try to word the Wikipedia articles so as to express, alongside one another at every step, both the ordinary language and loose usages, and the strict technical physical definition.

Not all engineers consistently follow the ordinary language usage as contrasted with the strict technical physical definition. Engineers are practical people.

The term "internal energy" does not appear in the Wikipedia article Transport phenomena cited above by editor 201.204.200.18. This is a signal that the article is hardly about thermodynamics, and that the distinct thermodynamic concept of internal energy is not important for that article. This is not out of line. Many transport phenomena can be well considered without reliance on thermodynamics as such. I suppose that article was largely written by engineers, or by physicists with interests in statistical mechanics. In statistical mechanics, one also finds that mostly the word heat refers to what a thermodynamicist would call internal energy. This is because it is only in special problems that there arises the need for words to make explicit the distinction, between a process of transfer of energy as heat, and the internal energy of a body in a particular state. Nevertheless, it is not possible to give a consistent account of thermodynamics without careful distinction between those two concepts. Again I say that it would be devastatingly complicated and confusing to try to word the Wikipedia articles that refer closely to thermodynamics so as to express, alongside one another at every step, both the ordinary language and loose usages, and the strict technical physical definition of heat. For myself, I just avoid trying to edit articles that seem to have the ordinary language usage thoroughly established within themselves. An insistence that the ordinary language and engineering usage should prevail throughout, or that a mixture of terms should be accepted throughout, would cripple the Wikipedia in specific reference to thermodynamics.Chjoaygame (talk) 04:23, 14 November 2012 (UTC)

Chjoayme misundertands some basic facts. Probably he is not well versed in physical chemistry and heat transfer. Heat transfer is a discipline that deals with the transfer of energy as heat between different systems. Heat is transfered by three different phenomena (radiation, convection and conduction). Convection has not been reduced to the other two. There are specific dimensionless numbers that deal with the situation of wether, in a fluid, conduction of convection dominate (Rayleigh Number). I would agree that "heat transfer" and "heat" should be treated separetly, one being a fundamental aspect of the first law of thermodynamics and it's may interpretations and the other being related to the mechanistical aspects of heat transfer. The wiki's article on Transport Phenomena might not talk about enthalpy, but enthalpy and entropy are an important part of the study of Transport Phenomea. A peak at the literature would be enough. I do think that articles on thermodynamics should encompass the wide variety of concepts that curren--186.32.17.47 (talk) 16:26, 14 November 2012 (UTC)tly are involved in the subject, where there are different perspectives and that articles on thermodynamics should be more about current physics thought and not about other subjects. i.e. "heat transfer" and work in a mechanistical sense might be better of in articles proper to that subject, as engineering perspectives on the subjects that should be present on engineering topics not on physics topics. --186.32.17.47 (talk) 16:03, 14 November 2012 (UTC) I might not have made myself clear: when I talk about "heat transfer" I am talking about the _discipline_ related to the study of the transfer of heat; which of the different forms of heat transfer prevails in a given case, how is heat transfered, the _dynamics_ of it. That discipline is not centered around thermodynamics, altough how "far"· the system is from a thermodynamic equilibrium is important. The point I am trying to make, if it accounts for anything, is the difference in the disciplines of "heat transfer" and, in general "transport phenomena" and thermodynamics. This article (an article about "heat") is, I believe, an article _about_ _thermodynamics_ whereby, the article on "heat transfer" deals with that subject. Still I sustain that, if one is going to mention "heat transfer" convection and advection are important and should be considered as part of the forms of "heat transfer". If one reads the article on "heat transfer" it is inconsistent with the article on "heat" regarding the different mechanisms of "heat transfer". That is, more or less, what started this discussion. the mechanism of convection might make it difficult to establish, in a thermodynamic sense, what work is being done inside the system, how enthalpy moves in the system, etc. This is complicated by the limited applicability of the framework for fluid dynamics (Navier Stokes existence and smoothness) when there is turbulent flow of a compresible fluid. As it says in "http://en.wikipedia.org/wiki/Turbulent_flow" Nobel Laureate Richard Feynman described turbulence as "the most important unsolved problem of classical physics."[1]. I do believe the distintion between "heat" and "heat transfer phenomea" might be established in the article so as to not confuse the reader of both articles ("heat" and "heat transfer"). The concept of what is _heat_ in the physical thermodynamical sense and what is studied under "heat transfer" could be clarified so as not to confuse the reader. I do appreciate a lot Chjoaygame detailed description above on convection and how it involves different concepts (work, heat and internal energy) and why relating this to "heat" could bring confussion.--186.32.17.47 (talk) 16:26, 14 November 2012 (UTC)

There is no reason even to bring up the mathematically complicated natural/free convection when forced convection (the common type that happens in car radiators) works just as well as illustration. Chjoaygame is technically and perfectly correct that only internal energy (not heat) can be advected as a bulk flow of matter containing energy within it and moved from here to there. That means heat pumps don't really pump heat but rather energy. Heat cannot because heat cannot be stored in matter since the amount of it there, cannot even be defined! If you can't put a number on it, you can't claim it's "real ".

Temperature and thus kinetic energy may play only minor roles in this, when energy of phase transitions is involved. For example water can be turned to steam and sent down a pipe to transfer energy by condensing somewhere else, and yet the temp changes are very small-- as small as you like for a given transfer. They are markers for direction of transfer but cannot be used to quantitate how much energy is moved. That's a clue that they aren't fundamental and are in no way the core of what is happening physically. Physically it is potential energy being moved, not unlike moving a charged battery from here to there. It actually has nothing to do with "heat" in a thermodynamic sense.SBHarris 18:46, 14 November 2012 (UTC)

Actually a "heat pump" _is_ a thermodinamic cycle that involves doing work in order to transfer heat from a colder body to a hoter body. Just see http://en.wikipedia.org/wiki/Heat_pump. THe Navier-Stokes equations are the equations used that describe motion in a fluid: it does not matter if flow is laminar or turbulent, if there is forced convection or natural convection involved at some point. In both the use of dimentionless numbers arise, in order to describe weather flow is laminar or turbulent. Such numbers as Reynold's number arise in forced convection and Grashof's number in natural convection. Of course the ammount of heat transfered from the heat source to the heat sink _is_ computable and computed all the time. Heat transfer is not a matter of temperature (heat is transfered isothermaly all the time. In Carnot's cycle heat is transfered isothermaly and work is done isentropicaly). See http://en.wikipedia.org/wiki/Carnot_cycle. SBharris might be well intended but he has deep confusions in regard to thermodynamics, temperature, heat, "heat transfer" and the like: this is clearly not his filed of expertise. --201.204.200.18 (talk) 22:50, 14 November 2012 (UTC)

Also see: "Convective heat transfer, often referred to simply as convection, is the transfer of heat from one place to another by the movement of fluids. Convection is usually the dominant form of heat transfer in liquids and gases. Although often discussed as a distinct method of heat transfer, convective heat transfer involves the combined processes of conduction (heat diffusion) and heat transfer by bulk fluid flow, a process technically called heat advection." http://en.wikipedia.org/wiki/Convective_heat_transfer#Newton.27s_law_of_cooling I do understand that Heat "in a thermodynamic sense" is one thing and the discipline of the study of "heat transfer" in a mechanistical way are different things. What I am pointing out is that _it_might_ be called for to clarify that, in the article on heat it says "In physics, there are two kinds of thermal interaction that account for heat transfer: conduction,[4] and electromagnetic radiation.[5]" But the link to heat transfer reads "Heat transfer is a discipline of thermal engineering that concerns the generation, use, conversion, and exchange of thermal energy and heat between physical systems. Heat transfer is classified into various mechanisms, such as thermal conduction, thermal convection, thermal radiation, and transfer of energy by phase changes. Engineers also consider the transfer of mass of differing chemical species, either cold or hot, to achieve heat transfer. While these mechanisms have distinct characteristics, they often occur simultaneously in the same system.". So the "heat transfer" that is been refered in this article on heat, and the "discipline" of "heat transfer" that is being refered to in the other article seem to be _different_ things. --201.204.200.18 (talk) 00:02, 15 November 2012 (UTC)

Editor 201.204.200.18 writes: "the "heat transfer" that is been refered in this article on heat, and the "discipline" of "heat transfer" that is being refered to in the other article seem to be _different_ things". Yes, I think that is fair comment.Chjoaygame (talk) 06:07, 15 November 2012 (UTC)

engineering and physics and chemistry article in Wikpedia

There are many ways in which the word heat is used. In ordinary language it has a very diverse range of meanings. In technical writings in natural sciences and engineering there is still a range of meanings. Different fields use the word differently. The acute problem here is that there is a difference in usage between engineering and physics. In the strict physical technical definition, heat is a process word, not a state word; to put it in ordinary language, in the strict physical definition, heat is not a substance that might be transported by convection. In the usage of many but not all engineers, the word heat does duty also for internal energy in the context of convection. Some Wikipedia articles are written with the (non-universal) engineering usage that says that heat can be convected, which also agrees with ordinary language. Some Wikipedia articles are specifically concerned with thermodynamics, and they would be crippled if forced to accept the (non-universal) engineering usage. In thermodynamics, the distinction between heat and internal energy is fundamental and calls for ready access to a customarily accepted and logically rigorous terminology. This kind of distinction is not so urgent for engineers, who are practical people who know intuitively what they are talking about without depending on a rigorously logical terminology. I am not familiar with the engineering literature, but I have observed that to some extent engineers seem to differ in how they talk about such matters. I don't know what is the background of editor 201.204.200.18, but it is clear that he is of the school of thought that it is proper to say that heat can be convected, and it seems that he thinks that those who find that language not convenient for thermodynamics don't know what they are talking about.

It is hard to find solutions to such problems. One solution would be to let each article announce clearly its own frame of language, without insisting that all Wikipedia articles accept the same frame of language. To some extent that is the situation that prevails at present. Editor 201.204.200.18 cites Wikipedia articles that accept the usage that heat can be convected, and he speaks of the discipline of heat transfer. Evidently the users of those articles are not troubled by the concerns of logical rigour that concern some thermodynamicists. I suppose those users are practical people. But some Wikipedia articles find inconvenient the usage that heat can be convected, and such articles use the strict technical physical definition, which carefully distinguishes heat from internal energy. I do not try to edit the articles that thoroughly accept the usage that heat can be convected, because I don't think it would be useful for me to do so. Editor 201.204.200.18, as I understand him, is suggesting that the articles that currently do not follow that usage should think about changing so as to follow it in future. I have repeated my view that for articles with a strict thermodynamic concern, to follow that usage would be damaging.Chjoaygame (talk) 00:20, 15 November 2012 (UTC)

I have now made an edit, which is probably overkill, but might be a start to resolving this problem?Chjoaygame (talk) 00:42, 15 November 2012 (UTC)

I find myself in the odd position of arguing against the same point of view that I myself held a couple of years ago, and that you talked me out of. So I'm playing St. Paul here, preaching the new gospel to the unconverted. But I used to be a persecutor of that new point of view. Sigh.

Looking at it from the point of view that heat and work are not state variables, but a state variable change is only the sum of them (the change in internal energy is due to the sum of work and heat), I find it a little sweet and naive how people just imagine that objects "contain" a given amount of heat. Or thermal energy. They don't. Objects contain energy, but one cannot say how it got there. It could be any combination of work and heat (many paths) and you'd have the same object at the same temperature, and could tell nothing about its past. So how could you imagine you could recognize how much heat it took to get there? And that you can know what that amount is (therefore) contained, NOW?

And that when you transfer that energy, using the object as an advective vehicle, you can say you transfered heat when you transfered the object (as happens in convection). And that in heat pumps, the heat you transfer is the SAME heat, which is what the idea of "transfer" suggests.

It's sort of like the guy who puts money in the bank and does a wire transfer to somebody else in another state, and they get money, and the first guy is convinced that the money the other guy gets at Bank#2 is the SAME currency that went in the other end, at Bank#1. He's convinced that there is something special about the bills he put in. So that even if the guy at the other end gets more, due to some bank error, the first guy will be convinced that he got some extra bills of the bank's PLUS the first guy's bills.

In thermo, there's a conservation law for energy, but none for heat. So heat is like $100 bills that can be turned into other types of money. It can be transfered, but most interesting money transfers don't transfer driving around currency (physical notes) in an armored car, but rather 1's and 0's that are generated by (converted from) currency with name-attached at my end, and then get turned back into currency with somebody's name attached, at the other end.

Take a heat pump. It need not involve a phase change. A simple heat pump has a gas absorb heat from a cold reservoir, then you do work on it to raise the temp, and run it past the exchanger at the warm reservoir, where it dumps energy as heat because it's hotter than the warm reservoir. Then you let it expand until it's colder than the cold reservoir, run it back to the cold reservoir to absorb more heat, and repeat. You convince yourself that you're transporting heat from cold to warm, even though some extra heat appears at the warm due to your work (which you pretend has been transformed into heat). But that view pretends that heat is some "thing" that can't be created or destroyed. You're transferring energy (money) not bill and coins (work and heat)!

You can do endless variations. Suppose I compress a gas in a cylinder until it gets adiabatically hot, then transport it across town and extract the same work I put in, as an adiabatic reversible process. It his "heat transfer" just because the gas is hot during transport? I never put heat in, and I never pulled heat out, so how can I be transferring it? I think it would be better to call this "work transfer," not heat transfer! ;). If you don't believe a substance can have "thermal content" that is definable, then heat pumps don't even have heat at some point in their cycles, since all they transfer is fluids and gases containing internal energy, which is like money-- an intangible. No heat exists in them. The heat is gone. Heat is like currency-- it exists at one end of a wire transfer and also the other end, but in between, it's 1's and 0's. Still money, but not currency. It's money transfer, not currency transfer. SBHarris 03:14, 15 November 2012 (UTC)

For sticklers for grammar, one can happily say, I think, that, between closed systems or bodies, energy is transferred as heat and as work. It is but a short step from there to speaking of heat transfer. Perhaps a dangerously short step?Chjoaygame (talk) 04:24, 15 November 2012 (UTC)

It's easy to define heat transfer-- that's just heat. Not so easy is heat content (thermal energy). If no work is done you can "pretend" that all change in internal energy is thermal energy, like it was stored as "heat". This does no harm. But when work is done, it's bad. It takes less heat to raise the temp of a gas sample at constant volume than at constant pressure . When you get done you can let the constant volume one expand freely doing no work to the same volume as the other. Now you have identical samples but put more heat into one than the other. You cannot tell a sample's heat content from its state. It isn't how much heat you put in to warm it because this is variable (some got tapped off one sample as "work" here). Thermal content is an imaginary thing if you think it's related to heat input. The minimum possible input is just the internal energy change so why not just call it that (energy change) and leave "thermal energy change " to the boneyard.SBHarris 18:55, 15 November 2012 (UTC)

From what I can gather I agree with Chjoaygame: the notion of "heat" in the rigorous physical and thermodinamical sense is _one_ thing. What in (mostly engineering and some applied physics and chemistry: physical chemistry) is regarded as "heat transfer" is another thing. "heat transfer" is a "discipline" in as much as it _is_ a topic in engineering and some applied science. I studied Chemical Engineering back in the 90's. We did take a couple of years of physics, more or less 4 years of chemistry, including physical chemistry, a year of thermodynamics, a semester of transport phenomena, a semester of heat transfer, a semester of fluid dynamics, a semester of chemical reaction engineering, a year of mass transfer, about a year of chemical engineering design courses, among other things (calculus, linear algebra, differential equations, statistics, and the like). That is from where I heat the concept of "heat" in a thermodynamic point of view (mostly classical thermodynamics altough we did study some statistical thermodynamics also) but also of "heat transfer" as distinct discipline, in as much as engineering mechanics is a distinct discipline. Of course the concepts studied in the study and behavior and design of equipment in "heat transfer" are not _the_same_ as the rigourous definiton of "heat" in thermodynamics. Actually that is the main point that can be gather from the distinction. It is true that in a matter so complex as "convection" where different concepts are at play at the same time (the movement of the fluid as it absorbes energy, increases it's temperature, reduces it's density and moves, forced convection, heat conduction, even radiation that might be transmited within particles of the fluid) is _simplified_ in engineering in order to be able to _design_ equipement. Thus, the discipline of the study and _design_ regarded as "heat transfer" is distinct from the concept of "heat" in thermodynamics; similary as the notion of, i.e, fluid dynamics and the design of equipment is distinct from the concepts related to "work" and "enthalpy" and "internal energy" from thermodynamics, or even the rigourous study of mechanics in _physics. But I also would point out that turbulent flow (where "convection" usually is more important than "conduction"), specially where fluids are compressible and even more where they are not newtonian. The Navier-Stokes equations are not proven to be smooth or even to have solutions in all cases. This kind of situation makes the study of the mechanics of mass and heat momentum transfer specially complicated in these instances. I do not think, at all, that "it is proper to say that heat can be convected, and it seems that he thinks that those who find that language not convenient for thermodynamics don't know what they are talking about" I actually quite agree with Chjoaygame in what I understand of what he is writing. My _only_ point was that this difference of concept between what is studied under the discipline of "heat transfer" and what "heat" is on a thermodynamic sense _are_ different things. I also find his writtings above quite deep and interesting (for what that matters, even if it is not the main point of the wiki, they have made me a little bit wiser in regards to thermodynamics). In regards to Sbharris argument that one can´t calculate the ammount of heat that is being released in a process: there are different ways to calculate this variable. It is not true that only variables of state can be calculated. i.e. the ammount of work done is the _path_ integral of a force through a distance (δW=F●vδt). With regard to "heat", the amount of heat transfered through conduction can be calculated by Fourier's law (http://en.wikipedia.org/wiki/Thermal_conduction)

${\frac {\partial Q}{\partial t}}=-k\oint _{S}{{\overrightarrow {\nabla }}T\cdot \,{\overrightarrow {dA}}}$

where (including the SI units)

:${\big .}{\frac {\partial Q}{\partial t}}{\big .}$ is the amount of heat transferred per unit time (in W) and

:${\overrightarrow {dA}}$ is an oriented surface area element (in m2) In the case of radiation see (http://en.wikipedia.org/wiki/Thermal_radiation). Of course that, for a given process, if one has the functions of state for the system previously defined for two equilibrium states and has the ammount of work done one can use the first law of thermodynamics to calculate the ammount of heat. Since, i.e. δW=F●vδt and dE=δW+δQ one can calculate the ammount of heat. E is a function of the state of the system (it's position in gravitational or electromagnetic fields, i.e, it's kinetic energy, i.e., temperature, pressure...) if the effect of the force is known work is known. Only solve for Q. In the case of the heat pump there is an ammount of energy transfered from the sorroundigs to the system in one end that _is_ calculated and an ammount of work provided to the system that _is_ calculated. Thus, by the first law of thermodynamics, heat rejected to the heat sink is basically (ideally) the ammount of heat extracted from the heat source plus work done on the system, on each cycle. I really don't see the point or understand the reason for the comparissions of thermodynamics and money transfers. They do not make sense to me: heat, heat transfer, work, etc. are not "like" anything else, they are what they are. What the first law of thermodynamics states is that energy is conserved and it is transfered by one of two "transfer quantities" work or heat. The total change of energy of the system is _equal_ to the ammount (net) work done by the sytem plus the ammount of (net) heat released from the system. Energy is a function of the _state_ of the system. Work is a a scalar quantity that quantifies energy used when a force is applied through a distance (function of the path, not the state). Heat is a scalar quantity that cuantifies energy dispersed by the system that is not used to perform work. The second law of thermodynamics defines de minimum ammount of heat that must be dispersed in a change in the state of a system (TdS). Equivalenty the first law "forbids" perpetual motion of the first kind and the second law "forbids" perpetual motion of the second kind. I do not know where SBHarris gets the idea that functions of path can't be calculated and functions of state can. All of mechanics deals with _calculations_ mostly related with functions of _path_ (not state). There are also mechanistical calculations regarding heat as Fourier's law, heat equations, convection-diffusion equations, newton's law of cooling (which is a special case of fourier's) and radiative heat transfer. — Preceding unsigned comment added by 201.204.200.18 (talk) 19:36, 15 November 2012 (UTC) Thank you editor 201.204.200.18 for this comment. I am sorry I misread you. My excuse has to be that I was starting at shadows.Chjoaygame (talk) 20:10, 15 November 2012 (UTC) naughty, naughty I won't get into the article on thermal energy, but I think I have a naughty, naughty own research synthesis idea about it. There are two genera of characteristic functions, the thermodynamic potentials, and the Massieu-Planck functions. The thermodynamic potentials may be regarded as the internal energy and certain of its Legendre transforms, as functions of their natural variables. In a sense, these are all 'thermal energies', and when people speak of thermal energy they seem to me to be referring implicitly or tacitly or vaguely to some or all of these energy functions, not wanting to bother to think out which. The point is that 'thermal energy' can be thought of not as a particular or specific quantity, but as a genus of characteristic functions. This I think makes some sense of the usage, but I have not seen any hint of this thought in the literature. It is truly naughty, naughty.Chjoaygame (talk) 13:53, 15 November 2012 (UTC) Waleswatcher's current round of edits I disagree with Waleswatcher's current round of edits. The present problems of the article are largely due to the defects of his previous round of edits, which his current round of edits is more or less restoring. Waleswatcher seems to think he can edit at his whim, disregarding the views of other editors and not bothering with what appears in the talk page. He seems not to understand the questions at issue.Chjoaygame (talk) 16:11, 15 November 2012 (UTC) So you disagree Chjoaygame, do you? Are you going to tell u what you find disagreeable? Or are you just informing us about your latest dose of verbal flatulance? Please, please address the subject of the article and not the state of your digestive tract!--Damorbel (talk) 20:55, 15 November 2012 (UTC) The lead as it was did not summarize the article, was too long, was full of extraneous words and phrases, spent an inordinate amount of text discussing semantics, and overall was poorly written. The purpose of this article is to describe a basic concept in physics, not to give the history or discuss semantics. As such, the article - and especially the lead - needs to be written clearly and in a way that's accessible to a non-expert. My edits were a constructive attempt to improve those problems. You reverted them. I made another attempt, which you again reverted. If there is something specific in the lead as I have edited it that you disagree with, the appropriate action is either to edit that part specifically or discuss here. You do not own this article. Waleswatcher (talk) 16:39, 15 November 2012 (UTC) As usual, Waleswatcher you are behaving as if you own the Wikipedia, and your editing is destructive, violent, wrong in content, and written dictatorially with disregard for the views put on the talk page. You seem to lack insight into the character of your behaviour. There are very many things in your current round of edits that I disagree with.Chjoaygame (talk) 20:02, 15 November 2012 (UTC) Look in the mirror, Chjoaygame. "There are very many things in your current round of edits that I disagree with" - and yet, after three reverts and two talk page comments, you have yet to name a single one. Waleswatcher (talk) 03:11, 16 November 2012 (UTC) Waleswatcher, the view that heat can be produced and convected belongs to ordinary language and to some engineering writing, but not to the strict thermodynamical definition of it. I suppose you will here have a supporter of your view in the redoubtable Damorbel. I did not know this at the time, some time ago now, that I posted the details and references that you have re-posted about heat production and convection; at that former time I was not reading the texts with enough critical acumen. I am surprised to learn now that you are not well aware of this, because till now I had supposed that you were more or less well-informed. Till now I thought you were simply careless, but now I know that you lack insight. I am flattered that you re-post my obsolete material without question; thank you for this kind compliment. Nevertheless it is obsolete and should be deleted. As for variety being better English than diversity, I suppose it is a matter of taste. As for thermodynamics deserving special mention, there has been much talk on the talk pages from people interested in the "discipline of heat transfer" which more or less does without thermodynamics, while occasionally popping a bit of it into their calculations, not quite being aware when they are using it or when they are not using it. You say that all heat is in thermodynamics, so that it doesn't need to be mentioned up front. That may be obvious to you but it won't be to your non-expert reader. I don't think it was clear to all editors here until the recent round of discussion of it on the talk page. Your sentence about semantic interchangeability seems badly worded to me, and is by your criteria hardly needed in the lead.Chjoaygame (talk) 04:53, 16 November 2012 (UTC) I don't know what you're talking about even in your very first sentence. Where did I write that heat can be produced? Convection (to pick one example) is an important mechanism for heat transfer and is discussed in the article. Heat is transfer of energy by thermal interaction, and that's what convection is. I don't and didn't object to mentioning thermodynamics in the lead - on the contrary. Simply, that sentence was awkward and poorly formed. In fact, it can still be improved, and I will do so now. Waleswatcher (talk) 11:28, 16 November 2012 (UTC) Now, in _thermodynamics_ heat is a transfer quantity when there is a gradient in temperature. "heat" is not contained in any substance, in as much as work is not "contained" but exerted upon a system. There is a _confusion_ between "heat" and "thermal energy", thermal energy being internal energy dependant on temperature. The problem is that it is imposible to distinguish the different "kinds" of internal energy contained in the system: what one knows is that the system has a possibility of accumulating energy that is usually a function of temperature. i.e. an isothermal phase transformation within the system would not affect it's temperature. — Preceding unsigned comment added by 186.32.17.47 (talk) 16:13, 19 November 2012 (UTC) The state of the Heat article It should be made clear that there are many mistaken contributions to the various Heat articles (Thermodynamics etc.) and their discussion pages trying to present thermal physics as sommehow 'unconnected' to the energy of the individual particles making up a (thermal) system. This would indeed make quite funny joke if Wikipedia was not seen by most people as a valuable work of reference. If thermal physics is to reject the 'energetic particle' nature, then atomic theorywill have go with it. It was only when, 88 years later, Einstein linked the (Brownian) motion (1827) of pollen grains with the thermal motion of molecules (in one of his 1905 papers) and Marian Smoluchowski (1906) brought the solution of the problem to the attention of physicists, and presented it as a way to indirectly confirm the existence of atoms and molecules. Their equations describing Brownian motion were subsequently verified by the experimental work of Jean Baptiste Perrin in 1913. The (energetic) movement of particles may well be free, as in a monatomic gas; it may be partially constrained as with the motions of molecules when the energy may be in rotational dipole motions; in weak bonds as in liquids or strong bonds as in solids e.g. crystals. The energy in these bonds is released when the bonds are broken. This energy is generally called latent heat which can be misleading since bond energy does not involve motion, that is why solids are solids! The (average) position of particles in a solid is fixed, that is why solids are solids! But in their fixed (relative) positions the particles have mass and their thermal energy causes them to vibrate when they exchange their kinetic energy with the (elastic; potential) bond energy that holds them in place. The particles of solids have multiple bonds holding them in place and the energy of particles is shared by the forces along these multiple bonds, that is one of the ways heat is transmitted in solids) check with Phonons. So please, contributors, take these fundamental facts of atomic theory of matter into account when contributing to therml articles in Wikipedia and let us get rid of the errors and verbal pap in the current articles. --Damorbel (talk) 07:28, 16 November 2012 (UTC) Dear Damorbel, Editors PAR and 201.204.200.18 have been generous with their time and expertise to explain eloquently for your personal benefit the difference in the natures of thermodynamics and statistical mechanics.Chjoaygame (talk) 10:05, 16 November 2012 (UTC) Chjoaygame, what is this supposed to mean? What you have written above does not in any way respond to what I wrote at the beginning of the section. You may feel a warm glow of fellowship with editors PAR and 201.204.200.18 but you above do not present any argument or reason why heat should not be considered the (microscopic) energy of particles, which is a matter I suggest be included in the Heat article. Do I understand correctly that you are continuing to edit here while refusing to discuss this? --Damorbel (talk) 14:46, 16 November 2012 (UTC) I think Damorbel's point is that the article should spend more time discussing the microscopic/statistical mechanical origin of heat. Is that what you meant, Damorbel? If so, I fully agree. People coming to read this article want to know what heat is. Fundamentally, heat is described in terms of molecules, photons, etc. There should be more than one small section buried near the end of the article that discusses that. It's far more important to explain that than it is to bloviate endlessly about semantics and definitions. Waleswatcher (talk) 11:59, 16 November 2012 (UTC) Yes, but I think Darmobel would disagree with the fundamental definition of heat. There is a certain practical point about the way heat ended up being defined in the way it is in modern textbooks (e.g. the book by Reif), and the arguments here with Darmobel in the past about the definition have missed that point entirely. The point is that a physicist or engineer who is focussing on some macroscopic system would prefer to have a closed description of the system in terms of parameters that refer to the macroscopic properties of the system. But the laws of physics don't allow you to do this, the macroscopic degrees of freedom that you are interested in will be coiupled to the microscopic degrees of freedom. Then what you do is you attempt to describe the latter statistically. Energy transfer due to the degrees of freedom that you describe statistically that you don't keep explicit track of is, by definition, heat. So, heat arises when giving a coarse grained macroscopic description of a system. Without course graining you would (formally) describe the system in terms of its miscroscopic variables, but then everything is work and there is no heat anymore. The so-called "fine grained entropy" of a system is zero and it always remains zero, as there is no information loss at the fundamental level. What is heat thus depends on which degrees of freedom you throw away when doing the coarse graining, but in practice when you are only keeping one or two degrees of freedom and throw away the 10^23 other degrees of freedom, you don't notice this. The mistake Darmobel is making, is ignoring this subjective aspect of heat, pretend that it is a fundamental property of a physical system, and then attributing heat to energy stored in specific degrees of freedom. This is where all the misguided arguments about part of the internal energy being heat etc. start from. Count Iblis (talk) 17:27, 16 November 2012 (UTC) Count Iblis, a lot of time will be saved if you could say if "thermal physics is a function of the motional energy in the individual particles making up a (thermal) system." --Damorbel (talk) 19:25, 16 November 2012 (UTC) Count Iblis, I agree with everything you say regarding physics. I think we need a section near the beginning of the article that explains in simple terms what the connection is between heat, the macroscopic quantity, and microscopic physics. Everyone has an intuitive sense of the properties of heat when applied to human-scale objects, and everyone knows that things are made of molecules, so I think the best way to do that is using ordinary materials made of molecules as an example. This will also serve to illustrate the difference between heat and temperature which seems to cause so much confusion. I added a sentence to the lead that does that very briefly. But it's not something that should be explained in the lead, or at least not only in the lead. If you have time, would you take a shot at writing such a section - or expanding the one on stat mech that's there now? Otherwise, I can do it. Waleswatcher (talk) 19:44, 16 November 2012 (UTC) There are two concepts at interlpay here: one is the general theory of equilibrium thermodynamics. The other is it's concordance with the macroscopic effects of microscopic particles. i.e. there is "entropy" in the study of information systems, in informational physics, in gravitational aspects of nature, but we do not have, as of yet, a theory that unifies a theory of gravitation with quantum mechanics. What is _wrong_ is to claim that the theory of thermodynamics _requires_ or _is_based_upon_ statistical mechanics. It was developed well before statistical mechanics and the relation of both was established afterwards. If one is to believe that, according to all human experience, the laws of thermodynamics hold this does not have much to do with wether statistical mechanics hold. Of course if statistical mechanics hold true and they _contradict_ the laws of thermodynamics then these laws would cease to be general laws of the universe. But, up until know, quantum theory, the general theory of relativity, information theory, information physics, all seems to agree with the generalizations made by thermodynamic equilibrium theories, well before the other theories came around. We still have to see what dark matter, dark energy and other aspects of the universe hold for us, but, up until now, the basic laws and principles of classical thermodynamics hold true, and they are compatible with statistical thermodynamics (i as much as I know of).--186.32.17.47 (talk) 15:57, 19 November 2012 (UTC) distinction between thermodynamics and statistical mechanics Thermodynamics and statistical mechanics are both important in physics. Their relation is worth looking at. PAR and editor 201.204.200.18 have very kindly written something about this above here. Count Iblis also has views on this. The difference between macroscopic variables and microscopic variables is worth looking at here. One is concerned with a body of matter. Microscopic variables usually refer to particles, such as atoms, molecules, electrons, and many others. Macroscopic variables do not refer to particles. They refer to quantities that can be measured by certain kinds of macroscopic apparatus in the laboratory. Thermodynamics is particularly concerned with macroscopic apparatus that allows control and knowledge of the mechanical and chemical states of a macroscopic body. The control is considered to be exerted from outside the body. The knowledge is considered to be entirely provided by the history of the external controls. The individual particles within the body are considered to be inaccessible, both as to knowledge and as to control. In contrast, statistical mechanics is built on assumptions of knowledge and on measurement of the adventures of the individual particles of the body, as well as on the concerns of thermodynamics.Chjoaygame (talk) 21:24, 16 November 2012 (UTC) In a small sample of some textbooks of thermodynamics I found that the following do not mention Boltzmann's constant: Bryan, G.H. (1907). Thermodynamics. An Introductory Treatise dealing mainly with First Principles and their Direct Applications, B.G. Teubner, Leipzig. Buchdahl, H.A. (1966), The Concepts of Classical Thermodynamics, Cambridge University Press, London. Münster, A. (1970), Classical Thermodynamics, translated by E.S. Halberstadt, Wiley–Interscience, London, ISBN 0-471-62430-6. Pippard, A.B. (1957). The Elements of Classical Thermodynamics, Cambridge University Press Planck, M. (1923/1926). Treatise on Thermodynamics, third English edition translated by A. Ogg from the seventh German edition, Longmans, Green & Co., London. Prigogine, I., Defay, R. (1954). Chemical Thermodynamics, translated and revised by D.H. Everett, Longmans Green and Co., London. I found three that had sections on what they called statistical mechanics or statistical thermodynamics, which just in those sections did mention Boltzmann's constant: Adkins, C.J. (1968/1983). Equilibrium Thermodynamics, third edition, McGraw-Hill, London, ISBN 0-07-084057-1. Guggenheim, E.A. (1949/1967). Thermodynamics. An Advanced Treatment for Chemists and Physicists, (1st edition 1949) 5th edition 1967, North-Holland, Amsterdam.Chjoaygame (talk) 07:22, 19 November 2012 (UTC) Addendum of text quotes for the benefit of Damorbel Adkins (1968/1983) writes on page 78 about what he calls the discipline of Statistical Mechanics or Statistical Thermodynamics, and refers the reader to Kittel & Kroemer (1980). Kittel & Kroemer (1980) is entitled Thermal Physics. It is a textbook of statistical mechanics or statistical thermodynamics, as indicated by Adkins. Kittel & Kroemer give references to books on thermodynamics, including Pippard, A.B. (1966), of which they say "Very careful discussion". Reif, F. (1965) is entitled Fundamentals of Statistical and Thermal Physics. It is a textbook of statistical mechanics, not a textbook of thermodynamics. Amongst other books that it recommends for what it calls macroscopic thermodynamics it lists on page 632 Guggenheim, E.A. (1960), and Pippard, A.B. (1957). These and many other authors explicitly distinguish statistical mechanics from thermodynamics. For example, Callen, H.B, (1960/1985), Thermodynamics and an Introduction to Thermostatistics, John Wiley & Sons, New York, writes on page 5: "Like all sciences, thermodynamics is a description of the results to be obtained in particular types of measurement." Adkins (1968/1983) writes on page xi: "Many books and courses on thermal physics attempt to develop classical thermodynamics and statistical mechanics side by side. Although it is essential that the relationship between the two be established at some stage of a scientfic undergraduate's education, it is best to teach classical thermodynamics first and separately, for the ability to use it well depends largely on knowing what it can achieve without appealing to the microscopic nature of things." Regardless of Adkins opinions about the best way to teach, this shows unequivocally that he distinguishes between thermodynamics and statistical mechanics. Statistical mechanics in Adkins (1968/1983) is confined to section 5.6 on pages 77–86. Pippard A.B. (1966) on page 1 writes of ..."classical thermodynamics, the subject of this book. Here the method of approach takes no account of the atomic constitution of matter,...".Chjoaygame (talk) 12:29, 19 November 2012 (UTC) response by Damorbel Well? What is this supposed to show? I am quite sure it isn't in Alice in Wonderland either, despite the fact that Lewis Carroll was a logician and a mathematician. F. Reif writes in his popular work Fundamentals of Statistical and Thermal Physics :- (p136 - last para, 5th line):- "Careful measurements of this type yield for the gas constant the value R = (8.3143 +/- 0.0012)joules mole-1 deg-1 (4.3.8)" (p137 - top):- "(1 joule = 107ergs). Knowing Avagadro's number ("unified scale," atomic weight of C12 = 12 exactly) Na = = (6.02252 +/-0.00028) x 10-23 molecules mole-1 (4.3.9) One can use (4.3.3) to find the value of k. This important constant is called "Boltzmann's constant" in honor of the Austrian physicistwho contributed so significantly to the developement of kinetic theory and statistical mechanics. Its value is found to be * k = (1.38054 +/- 0.00018) x 10-16ergs degree_1" Now of course this is only one book in comparison with your eight but I have cited some relevant text, may I ask you to do the same for at least a few of yours? --Damorbel (talk) 08:56, 19 November 2012 (UTC) Damorbel, you cite one book on thermal physics with the word "Statistical" explicitly in its title. You make no attempt to cite a book on thermodynamics. Your evidence does not provide support for your mistaken claim that thermodynamics puts importance on Boltzmann's constant, but your evidence does provide support for the position that is the overwhelming majority consensus of the editors of this article, examplified by the tutorial work above, carefully and kindly supplied specifically for your personal benefit by editors PAR and 201.204.200.18. That overwhelming majority consensus position is that thermodynamics and statistical mechanics are distinct subjects with distinct methods. This is contrary to your mistaken view that thermodynamics has a main concern with Boltzmann's constant. It is regrettable that you continue to ignore the well considered reasons, carefully assembled for your personal benefit in some cases, why the dogma about Boltzmann's constant, that you continue to repeat and try to force on others, is not suitable as a viewpoint for the present article. The time editors spend trying to help you with your besetting fixed idea would be better spent on other things, but regrettably people feel sorry for your suffering with your besetting fixed idea, and they spend time trying to help you. Still and ever you reject their help. You quote from one book, an inappropriate one, ignoring the appropriate ones that I have indicated above, and then you ask me to quote from a few of mine. The best remedy for this, as I have suggested before, is that you do some reading for yourself, with an open mind, instead of petulantly demanding that we do your homework for you.Chjoaygame (talk) 12:51, 19 November 2012 (UTC) Do you have the citations from your books that I asked for ? You cite:- "carefully and kindly supplied specifically for your personal benefit by editors PAR and 201.204.200.18." And these are "reliable sources" as required by Wikipedia? "You make no attempt to cite a book on thermodynamics." Enrico Fermi Thermodynamics ISBN 13:978-0-486-60361-2 ; ISBN- 10:0-486-60361-X page 57, 3rdparagraph, from 4th line:- "Such a relationship was actually established by Boltzmann , who proved that:- S = k log π where k is a constant called Boltzman's Constant and is equal to the ratio, R/A of the gas constant R to Avogadro's number A." In your battle to show that thermodynamics is not connected to the Boltzmann constant, particles and Avogadro's number you could also try this link :- http://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/idegas.html You are insufferable, Damorbel. I provided above here some quotes as you petulantly and lazily demanded, but you did not read them. Here they are again. Adkins (1968/1983) writes on page 78 about what he calls the discipline of Statistical Mechanics or Statistical Thermodynamics, and refers the reader to Kittel & Kroemer (1980). Kittel & Kroemer (1980) is entitled Thermal Physics. It is a textbook of statistical mechanics or statistical thermodynamics, as indicated by Adkins. Kittel & Kroemer give references to books on thermodynamics, including Pippard, A.B. (1966), of which they say "Very careful discussion". Reif, F. (1965) is entitled Fundamentals of Statistical and Thermal Physics. It is a textbook of statistical mechanics, not a textbook of thermodynamics. Amongst other books that it recommends for what it calls macroscopic thermodynamics it lists on page 632 Guggenheim, E.A. (1960), and Pippard, A.B. (1957). These and many other authors explicitly distinguish statistical mechanics from thermodynamics. For example, Callen, H.B, (1960/1985), Thermodynamics and an Introduction to Thermostatistics, John Wiley & Sons, New York, writes on page 5: "Like all sciences, thermodynamics is a description of the results to be obtained in particular types of measurement." Adkins (1968/1983) writes on page xi: "Many books and courses on thermal physics attempt to develop classical thermodynamics and statistical mechanics side by side. Although it is essential that the relationship between the two be established at some stage of a scientfic undergraduate's education, it is best to teach classical thermodynamics first and separately, for the ability to use it well depends largely on knowing what it can achieve without appealing to the microscopic nature of things." Regardless of Adkins opinions about the best way to teach, this shows unequivocally that he distinguishes between thermodynamics and statistical mechanics. Statistical mechanics in Adkins (1968/1983) is confined to section 5.6 on pages 77–86. Pippard A.B. (1966) on page 1 writes of ..."classical thermodynamics, the subject of this book. Here the method of approach takes no account of the atomic constitution of matter,...". Fermi's little book that you cite is not a systematic treatise, but is a record of a series of visiting lectures. Even reading it, one sees that the comment you quote is a passing remark, not a statement of the main concern or method of approach of the thermodynamics, which is what you are trying to force down our necks. Your citation of Fermi like this is evidence of the vacuity of your endlessly and mindlessly repeated urgings, not evidence or argument in favour of your besetting fixed idea. No matter how much effort editors put into trying to help you with your problems, you refuse or are unable to see the obvious, so blinded are you by your besetting fixed idea. You are of course wrong to say that I am concerned "to show that thermodynamics is not connected to the Boltzmann constant, particles and Avogadro's number." Relevant here is not mere connection as you wrongly urge, but main concern and method of approach, which you fail to deal with. That you miss this point is evidence of your incompetence to edit Wikipedia in this area. As I have repeatedly observed in the course of repeated bitter experience of time wasted in replying to your posts, it is futile to read or to reply to your vexatious and irrational posts. Chjoaygame (talk) 16:39, 19 November 2012 (UTC) As a further comment on the relative reliability of Fermi's lecture notes, it was not, as implied by Fermi as cited by you, Boltzmann who first wrote S = k log π. It was Planck.Chjoaygame (talk) 16:43, 19 November 2012 (UTC) Chjoaygame, Sorry if you find my contributions insufferable but my understanting of your position is that you maintain that thermodynamics is not about particle physics. If you look at my references you will see that they show the connection very clearly. I find it rather sad that you dismiss Enrico's book (Fermi's little book that you cite is not a systematic treatise, but is a record of a series of visiting lectures) without reasoned argument. I could point out errors but I would need to reason them. Using this 'abuse' of Fermi (and Reif) to defend the crap in the article is not a positive contribution to Wikipedia, please stop writing this kind of 'stuff'.--Damorbel (talk) 21:54, 19 November 2012 (UTC) As usual, Damorbel, you get the physics wrong. Your statement that you are sorry looks like crocodile tears. Your statement of your understanding is ambiguous so that it will lead to errors of reasoning, which you actually commit. You say "my understanting of your position is that you maintain that thermodynamics is not about particle physics." This uses the word "about" in a two-faced way. Thermodynamics does not make particle physics the basis of its methodology, which is the point at issue here. But in another sense, that you intend to exploit, one can say that all studies of the properties of matter are "about" particle physics. Indeed, Fermi's little book of lecture notes is not a carefully constructed treatise on thermodynamics. To say so is not to abuse it, but is to recognize its actual character. As I have already pointed out, Reif's book is also not a carefully constructed treatise on thermodynamics; it is a student text on statistical mechanics. Damorbel, you fail to make this important distinction, and that you label my comments abuse because of your failure is further evidence of your incompetence to edit Wikipedia article of the present kind. Dear Damorbel, I expect it likely that you may offer further vexatious and irrational posts here about this, but I have spent enough time on trying to help you with your cognitive problem, called above your "mental block", that I call your besetting fixed idea. Partly following your request "to stop writing this kind of 'stuff'", I will likely now let you rattle on and have the last word on this right here.Chjoaygame (talk) 23:10, 19 November 2012 (UTC) further response by Damorbel Chjoaygame, did you not notice that none of your refs. state the heat is not the energy of vibrating particles? That is my position and the links I gave all refer to the Boltzmann constant which is the link between particle energy and temperature. It is no part of my argument that there are no differences between Statistical Mechanics and Thermodynamics but equally it is quite illogical to say, as the article does, that Heat does NOT involve the energy of particles. --Damorbel (talk) 08:21, 20 November 2012 (UTC) Sad to say, we know only too well that it is no part of your argument to say that there are no differences between statistical mechanics and thermodynamics. We can see only too well that you have no inkling of the difference and so cannot be expected to make it part of your argument. We have been hoping to get you to understand the difference, but our efforts are like water on a duck's back. Of course, when you say that the article says that heat does NOT involve the energy of particles, you are utterly mistaken. The article has a section that observes that the phenomena of heat are explained by statistical mechanics, which implies the involvement of particles.Chjoaygame (talk) 09:21, 20 November 2012 (UTC) Chjoaygame, you write "The article ... ..... implies the involvement of particles." Given the references I provided (which you dismiss) showing Heat should fundamentally be about the energetic movement of particles, why then does the article not acknowledge this in the main sections? The phenomena of hotness is historically an experience thaat all life has of the energy of particles and the article should indeed explain these experiences, but to absent from the opening section the 19th discoveries of Sadi Carnot, Count Rumford, Clausius and many others in the field of particle energy and ultimately the whole of atomic physics is frankly bizarre. The opening section should be mainly about the fundamentals of particle energy, it doesn't even mention it! A serious defect. --Damorbel (talk) 10:06, 20 November 2012 (UTC) Damorbel, the lead contains the following: "Heat is a characteristic of macroscopic processes and is described by thermodynamics, but its origin and properties can be understood in terms of microscopic constituents using statistical mechanics." That summarizes the content on the matter that is in the body of the article, and is enough in the lead for the purpose which you are advocating, I think. Or is it that you really don't know that statistical mechanics is essentially about energy and particles? You may or may not have noticed that I don't have much say about what is in the lead, what with Waleswatcher throwing his weight around and you continually and repeatedly and unethically sabotaging my efforts. You might try to get Waleswatcher to comply with your program of thorough reconstruction of the article, and see how you get on.Chjoaygame (talk) 10:31, 20 November 2012 (UTC) And just what is "Heat is not a property of a system or body, but instead is always associated with a process of some kind." mean when heat is the vibrational energy of the system particles? The vibration (or the collisions in the case of gases) are the motions that characterise the temperature(s) in a system. The relationship between particle energy and temperature is through the Boltzmann constant, the word Boltzmann des not even appear in the article! The article couldn't be worse if it was centered on green cheese. --Damorbel (talk) 11:14, 20 November 2012 (UTC) repsonse by editor 186.32.17.47 I do not know what is the problem here. There _is_ a general theory of thermodynamic equilibrium: that is _true_ and it goes before and beyond statiscal mechanics, but it is _compatible_ with statistical mechanics. What is the problem? Of course stastiscal mechanics is an important aspect of thermodynamic knowledge. But the general laws and principles of thermodynamics as established by, i.e, Gibbs, do not require statistical mechanics for their formulation (in as much as the general theory of relativity is not about quantum mechanics but they should be compatible somehow). I do not know what the disagreement is about. An article on thermodynamics should encompass the general equilibrium theory, with it's four laws and diverse principles: the universe that we have, derived from the work of Gibbs, Carnot, Clasius, etc., that is used to predict conditions of equilibria and steady state situations and functions of state with work and heat as functions of path, and also the development of statistical mechanics and it's compatibility and enhancement of thermodynamics (which is, in itself a great accomplishment of science). What is wrong is to pretend that all reasoning in thermodynamics is based on statistical mechanics. And also to pretend that thermodynamics is about the study of "heat transfer" (explicitly or implicitly). The mechanism of "heat transfer" is not that important in thermodynamics, safe, conduction and it's relation with statistical thermodynamics and radiation similarly. Mixed methods of transfering heat that involve mass transfer along with heat transfer (convection and advection) depend a lot on the definition of the system and are better placed in an article on "heat transfer", as calculations of work and energy and momentum in mechanics are better placed there, but the compatibility of science (up until know there is compatibility: we do not have a theory of everything that links quantum mechanics and gravitation nor we comprehend much about dark matter and dark energy, etc.) should be pinpointed to certain detail.--186.32.17.47 (talk) 16:29, 19 November 2012 (UTC) convection of heat There are various views on the notion of convection of heat. A a child at school I was taught that heat can be convected. Many engineers talk of convection of heat. The present Wikipedia article on heat transfer talks freely about the convection of heat, but does not contain the phrase 'internal energy'; it also talks freely of 'thermal energy'. The present Wikipedia article on heat cites two sources for the definition of heat, Kittel & Kroemer, and Reif. Kittel & Kroemer in their index have an entry "Convective isentropic equilibrium". It refers to problem set on page 179. The word heat does not appear in the text of that problem. Reif has no entry for convection in his index. In thermodynamics, the phrase 'convection of heat' might be anticipated to refer to open systems. In general, transfer of energy as heat is not defined for open systems.(Münster, A., 1970, Classical Thermodynamics, translated by E.S. Halberstadt, Wiley–Interscience, London, ISBN 0-471-62430-6, pp. 50–51. The index of this text does not contain an entry for convection.)Chjoaygame (talk) 22:05, 16 November 2012 (UTC) response by Waleswatcher What would you call the transfer of energy from a high temperature solid object to a cold gas surrounding it, and then to a colder container surrounding the gas? Waleswatcher (talk) 23:47, 16 November 2012 (UTC) Good question. It depends on how the transfer takes place. The system as described as a whole seems to consist initially of several bodies in thermal contact, initially at different temperatures. The problem as stated refers to a colder container, but does not explicitly say what determines the temperature of its walls, whether they are kept at controlled steady temperature or whatever. I will treat the problem as intending no external energy source, so that the system as a whole is isolated. It seems intended to assume that the solid body does not evaporate and the gas does not condense? If the temperature differences are small so that the process is very slow, it might occur without hydrodynamic instability, and thus without convection. Then conduction would be important, and radiation between the internal solid body and the walls might be significant. If the gas volume were very large, radiation within the gas might also come into it. If the temperature differences are larger, hydrodynamical instability might occur, and convection. Classical thermodynamics does not talk about intermediate stages of the process, but restricts its attention to the initial and final equilibrium states. The final equilibrium state is one of thermal equilibium, in which the temperatures of the several bodies are equal. Non-equilibrium thermodynamics could well take an interest in the intermediate stages of the process, and would be concerned with hydrodynamic stability and convection. Both bulk movement of the parts of the gas and conduction would be of much concern. The energetic quantity considered to be transported by bulk movement of parts of the gas would be depend on the variables chosed for the formulation of the analysis. Internal energy density would be suitable if the relevant variables were chosen. Some treatments, that did not respect the strict physical definition, would call that internal energy density a density of heat, and would talk of convection of heat; I think the Wikipedia article Heat transfer would likely do that. But you are asking me what I would call it. I would follow the strict physical definition, and call it transport of internal energy by bulk flow. If the convection were very strong, then turbulence might occur, and a precise thermodynamic treatment would not be feasible.Chjoaygame (talk) 02:27, 17 November 2012 (UTC) Enough time has elapsed to let Waleswatcher respond to this. He hasn't. It seems reasonable to infer that he concedes the point, that the strict thermodynamic definition of heat allows it to transfer itself only by conduction and radiation, and not by convection. Convection of heat is for some engineers and schoolboys.Chjoaygame (talk) 03:38, 20 November 2012 (UTC) response by Waleswatcher I've simply been very busy. I do not "concede" that point, nor is that point relevant. This article is not about "the strict thermodynamic definition of heat". It is about heat. Along with radiation and conduction, convection is one of the primary and common mechanisms of heat transfer. Therefore, this article should discuss it. Since the lead should summarize the article, it's reasonable for the lead to mention convection. Waleswatcher (talk) 12:54, 20 November 2012 (UTC) We have been patient while you attend to your important "very busy" activities, but we do not get the same consideration from you, in your habit of violent onslaughts in bursts of editing, that largely ignore the talk page, and overwrite contrary opinions as if you own the lead. For some time, the article suffered from your violent removal from the lead of the advice that the article is written from the technical viewpoint of physics, and especially of thermodynamics. Now you have conceded by your actions that your former removal was wrong. Your former removal of that reservation survived because other editors, though knowing it was wrong, did not wish to engage in the violent and unethical kind of editing that you inflict. So for a while you got your way by violence. The article is not, as you assert just above, about heat as read in ordinary language. It is about heat as viewed from the viewpoint of physics and chemistry, with thermodynamics of particular importance, as you now admit in the article. The lead you have inflicted on the article now seems smooth talk, as is your taste. But its logic is poor and fuzzy. The term 'thermal interaction', imposed by you, is an evasion, because the word 'thermal' is eventually not clearly defined. The references for the first sentence are from Reif and from Kittel & Kroemer, introductory student textbooks of statistical mechanics, that take the pedagogical viewpoint that thermodynamics should be taught simultaneously with statistical mechanics, but hardly mention the more serious parts of thermodynamics, such as Legendre transforms and the choice of working with energetic potentials versus Massieu-Planck functions, and thermodynamic stability theory. They do not consider convection as a form of heat transfer. The second sentence of the lead as it is worded could easily suggest to a naive reader that convection of heat is transfer by bulk flow of something that is conserved, and could be represented by a state variable of the bulk fluid, in contradiction of the vaguely worded third sentence of the lead, "Heat is not a property of a system or body, but instead is always associated with a process of some kind", which omits reference to the important idea that a property of a body is represented by a state variable, and leaves the kind of process unduly wide open. From what you write, it seems possible or even likely that you yourself do not understand that heat in physics, not being subject to a conservation law, cannot in logic be convected. Engineers can think in terms of convection of heat by considering restricted classes of process. While thermodynamics of open systems allows, in general, diffusion to occur where internal energy is also being transferred, or produced from external potential energy, engineers can deal with many of their problems by treating restricted processes which do not involve such simultaneous transfers, and so avoid the problems that a general thermodynamic treatment considers. Leaving convection there in the lead invites confusion, which is partly your aim, in order to evade a clarity that would expose your sloppy thinking.Chjoaygame (talk) 15:39, 20 November 2012 (UTC) Your talk page comments are as wordy and incoherent as your edits to the article. Waleswatcher (talk) 17:12, 20 November 2012 (UTC) Waleswatcher, you thus confirm your violent and unethical character. The talk page is too much for you. In particular, you offer no physical reason for your violently imposed view that heat can be convected, while you still say below to Damorbel that the definition of heat that we are using is that of physics, not of ordinary language.Chjoaygame (talk) 21:14, 20 November 2012 (UTC)Chjoaygame (talk) 21:27, 20 November 2012 (UTC) Wikipedia is based on reliable sources, Chjoaygame. Find us a source that states explicitly that radiation and conduction are the only mechanisms of heat transfer, and we can compare it to the multiple sources that say otherwise (and explicitly include convection). Until then, no such statement can be added to the article. Apart from wiki policy, the purpose of this article is to explain a basic concept of physics. People reading it want to know what's the underlying physics of heat, and why they feel warmth when they stand near a vent blowing heated air. Waleswatcher (talk) 12:00, 21 November 2012 (UTC) Dear Waleswatcher, you can spin this by violence and Wikilawyering, but you can't get the physics right.Chjoaygame (talk) 20:44, 21 November 2012 (UTC) response by Damorbel Chjoaygame your argument: the strict thermodynamic definition of heat allows it to transfer itself only by conduction and radiation is completely without foundation. Heat transfer is a subset of the processes that lead to thermal equilibrium. Thermal equilibrium is the condition where the temperature is uniform - full stop. Now a mole of an material contains 6.02214X×1023 (Avogadro's number) particles, I invite you to estimate how many ways these 6.02214X×1023 particles can go from any state of disequilibrium to equilibrium. Your idea that only conduction and radiation exist surely is not supported by the facts; does diffusion not play a role, particle collisions in gases. Equilibrium implies that the probability of a particle has a given energy is uniform throughout the system - that is what it's all about, not imginary restrictions. Oh, and don't forget there is no restriction on the size of the particles!. --Damorbel (talk) 08:08, 20 November 2012 (UTC) response by Damorbel Convection is mass transport in fluids in a gravitational field (a kettle of water, a planetary atmosphere) when a (mass) density differential arises due to thermal disequilibrium. Convection is not to be confused with forced convection which is quite distinct; in forced convection momentum is added to the system from an external source, the energy implied most likely being converted to heat by friction. --Damorbel (talk) 07:21, 17 November 2012 (UTC) Chjoaygame, you mention neither gravity nor (mass) density in your explanation of convection above; nor do you distinguish between convection and forced convection. I think these are important matters in regard to convection since they are all related to the concept of heat as energy in the motion of particles. I'm sure your omission was inadvertent and not on technical grounds. Thanking you in advance for your attention. --Damorbel (talk) 07:21, 17 November 2012 (UTC) I was not seeking to explain convection. I was seeking only to specify what might be convected. I was not trying to consider "a concept of heat as energy in the motion of particles". That is not the notion of heat that is considered in thermodynamics, the main theory for the present article. Dear Damorbel, we are all well aware that you would like to change the viewpoint of the article so as consider "a concept of "heat as energy in the motion of particles", but mostly we are not attracted by the idea; I think you are very well aware of this. Not even in statistical mechanics is that a very satisfactory definition, as you will find by reading some textbooks on the subject, with an open mind. We have mostly found by experience that our explanations here of the reasons for this do not satisfy you. That is why I suggest you do some reading for yourself, with an open mind.Chjoaygame (talk) 07:59, 17 November 2012 (UTC) Chjoaygame, "but mostly we [sic] are not attracted by the idea"; is of absolutely of no relevance to the Heat articles in Wikipedia It should be clear to all that the concept of heat is the relation of temperature and energy incorporated in the Boltzmann constant. As far as I can see the Boltzmann constant does not appear in your arguments. I suggest that until it does you will not be able to sustain them. Please comment. --Damorbel (talk) 08:33, 17 November 2012 (UTC) No comment.Chjoaygame (talk) 11:13, 17 November 2012 (UTC) This won't do, Chjoaygame. You dismiss my claim that a Wiki article on heat should be based on the energy of the particles of the system and when I invite you to discuss the key relation between particles, their temperature and energy - the Boltzmann constant - you reply 'No comment'. If you are not able to progress this discussion at such basic level, are you able to say how I am to respond to your contributions to the heat article? --Damorbel (talk) 11:41, 17 November 2012 (UTC) The basic level of discussion includes a fact that you will not absorb, which is that heat is not temperature, which is what the Boltzmann constant is about. To get from temperature to heat, you must consider the defining relation between them, which is heat capacity. This is a complex function which is not constant, not obvious, and which makes the whole matter of heat nontrivial and not capable of being easily defined in terms of temperature (and thus motion) alone. Okay? We've told you this a dozen times and yet it does not penetrate. What is your mental block? SBHarris 17:07, 17 November 2012 (UTC) response by editor 186.32.17.47 Heat is not based on the energy of the particles. Damorbel, you are confusing internal energy with heat. Heat and work are trasnfer phenomena, temperature is part of the state of the system. In classical equilibrium thermodynamic processes what one has is an equilibrium initial state and an equilibrium final state. In these internal energy is a function of temperature (and so of the microconfigurations of constituent particles), and also entropy, free energy, enthalpy, and other functions of state are functions of the microconfigurations of constituent particles. Transfer phenomena, mechanics, the study of heat tranfer, are another matter entirely, dependant on the process and used to provide descriptions of the dynamics of processes, not of it's equilibrium state conditions...--186.32.17.47 (talk) 16:49, 19 November 2012 (UTC) Incompatible statements? I suggest that these four statements in the article are not consistent:- 1/ "Heat flow from a high to a low temperature body occurs spontaneously." (Opening statement, 2nd paragraph) 2/ "The SI unit of heat is the joule." (Opening statement, 3nd paragraph) 3/ "Heat in physics is defined as energy transferred by thermal interactions." (Overview - 1st line) 4/ "The first law of thermodynamics describes the principle that the internal energy of an isolated system is conserved." (Overview - 1st line, 2nd paragraph) I invite comments since there appears to be no consensus on the physics involved. --Damorbel (talk) 07:55, 17 November 2012 (UTC) I do think that the first one is correct: if both systems are in thermodynamic contact heat will flow until both have the same temperature, either by radiation, conduction or more complex phenomena. Also the unit for heat is the same as the unit for energy and work (the joule). When there is a thermal interaction between two systems heat is transfered if there is a gradient of temperature. The first law of thermodynamics does state this and then can be generalized to a conservation of energy law and even a conservation of mass energy law (regarding the derivation of the equivalence of mass and energy of Einstein).--186.32.17.47 (talk) 16:58, 19 November 2012 (UTC) Thanks for you response 186.32.17.47 (I wish you had a name!) This section I started is really FAR TOO OBSCURE! I am trying to make the point that the article is self-contradictory. It is section 3/ that is the problem, You are quite right, section 1/ is OK. However, if the unit of heat is the Joule - section 2/ (energy - conserved) then it does not just appear during transfer, it is here all the time (sections 1/, 2/, & 4/. --Damorbel (talk) 21:34, 19 November 2012 (UTC) Nope: the unit of work is the Joule too and it is also a function of time. http://en.wikipedia.org/wiki/Joule "The joule ( /ˈdʒuːl/ or sometimes /ˈdʒaʊl/); symbol J) is a derived unit of energy, work, or amount of heat in the International System of Units.[1] It is equal to the energy expended (or work done) in applying a force of one newton through a distance of one metre (1 newton metre or N·m), or in passing an electric current of one ampere through a resistance of one ohm for one second. It is named after the English physicist James Prescott Joule (1818–1889).[2][3][4]" The first law of thermodynamics states that energy is conserved in an isolated system: the total change of energy of "the universe" (being the universe an isolated system) is always zero. Energy is a function of state. Energy is transfered between the system in study and it's sorroundings through two distinct quantities or phenomena: heat and work. Both, heat and work, are functions of _path_, both are dynamic quantities, both are not functions of state; heat and work are how energy is transfered between a system and it's sorroundings, not related to the energy content but to the transfer phenomena. According to the second law of thermodynamics there is a minimum ammount of heat that _always_ has to be transfered in order to "move" a system between two states: the process that uses up the minimum quantity of heat possible is a reversible process such as dS=δQrev/T. The "δ" means that it is not a function of state, that the differential is not an "exact differential", that it is a function of _path_. Most of the work of Gibbs and others is a mathematical framework to deal with exact differentials in equilibrium states and the relationships between G, T, S, U, H, A, and variables of state (T,P, Vmol, Ni) and amongst themselves, including the use of Maxwell relations http://en.wikipedia.org/wiki/Maxwell_relations between the second derivatives of thermodynamic potentials http://en.wikipedia.org/wiki/Thermodynamic_potentials. In order to simplify: first the system is in equilibrium, then there are some dynamical aspects that involve "heat" and "work" and then we have another equilibrium state. In a system in equilibrium with it's sorroundings there is no heat and no work performed. Heat and work exist as distinct path functions in a given physical process. The first and second law also imply the non possibility of perpetuum mobile. The confusion arises when (lacking proper thermodynamic discourse) such thing as "heat content" is instead of internal energy and or enthalpy. dH=δQ+VdP+δW' where if pressure is constant and δW' (other work, not related to pressure volume work) is zero then dH=δQ if the only work done is expansion work and there is no other work involved. But dH is a change in the _enthalpy_ of the system (a function of state: i.e. a function of the state of the system before and after a process that involves a certain ammount of heat δQ). That is one of the reasons why enthaply is so important in physical chemistry and thermodynamic equilibrium. In order to establish these relations there is no need to take into account statistical thermodynamics (even though they are compatible with it) nor is "heat contained" on any system ever. Heat is exchanged between the system in analysis and the sorroundings. --186.32.17.47 (talk) 22:25, 19 November 2012 (UTC) 186.32.17.47, Thank you for your reply. What do you mean by 'nope'? You write "the unit of work is the Joule too". Work, as you acknowledge is measured in Joules, it is the integral of force (Newtons) over a period of time, the joule is a measure of energy; energy is a conserved so when an amount of work is done the energy is transformed into another manifestation PVγ for a gas, δT xC (C = heat capacity in joules/K). But there are other manifestations of energy transformation, electrical and chemical energy can also be transformed into heat, the actions in this case may or may not involve time the heat (in joules) is equal to the chemical or electrical energy received from the source. How is "heat and work, are functions of _path_"? Chemical energy is not a function of path; electrical energy stored in the electrical field of a capacitor is not a function of path, neither is gravitational energy. Conserved quantities like energy are independent of path. A bit of clarifiation would be appreciated! --Damorbel (talk) 15:24, 20 November 2012 (UTC) "However, if the unit of heat is the Joule - section 2/ (energy - conserved) then it does not just appear during transfer, it is here all the time" = Nope. Heat, as work, as you clearly state, is a path function or a process function see: http://en.wikipedia.org/wiki/Path_function One thing is _heat_ which is a process function, another thing is _work_ which is another process function, another thing is energy which is a function of state. All are measured in joules. It seems to me you could not understand how thermodynamic analysis is done: one first must establish a sytem and an initial equilibrium state for the system. Then there is a process that changes the state of the system, generating an interaction with the system sourroundings that changes it's energy through work and heat. Finally there is another equilibrium state. Heat and work are processes where energy is transfered. The do not 'exist' when the process is not occuring and they are _path_dependent_. Energy is conserved, but it is transfered between the system and it's sorroundings through heat and work during a process. It is the energy of an isolated system that is conserved, not the energy of any system. If you divide the universe in two sytems ('the system of study' and 'the sorroundings' the sum of both sytems is an isolated system for the process that is being analyzed).--186.32.17.47 (talk) 16:06, 20 November 2012 (UTC) 186.32.17.47 You have not understood the argument being presented. Perhaps it would help if you told me what you call the energy of the vibrating particles in as system of particles when such a system has a uniform temperature and the particles are able to exchange energy freely. I ask this because, when you describe 'heat' as a process (above) you are not describing (nor is your link) a system with a uniform temperature but one with more than one temperature; so what you are describing is indeed a heat transfer process which is essentially a process in a system that is in disequilibrium. Calling this heat is a shorthand or jargon term; the full expression should be heat transfer the word transfer, standing as it does for disequilibrium, has been left out. --Damorbel (talk) 20:14, 20 November 2012 (UTC) reponse by Waleswatcher: Damorbel, there is nothing incompatible about those statements. Heat is indeed energy transferred by a specific means (thermal interactions). Can I make an analogy? You have a certain amount of money in your bank account, measured in euros. Your salary is money transferred into your bank account by your employer because of work you have performed. Your salary is also measured in euros. Energy is like the money in your account, while heat is like salary - they're measured in the same units, but they're not the same thing, and you would never refer to the money in people's bank accounts as "salary". Does that make sense? Waleswatcher (talk) 17:15, 20 November 2012 (UTC) Rubbish, Waleswatcher. What I have in the bank is money (I wish it was!). My salary is (a little) money per month, I have to integrate it wrt time before it becomes money. The money in the bank represents energy in the system, it is conserved (Oh dear!); whereas the income is a variable function of time from outside the system and may well not be predictable i.e. it is not conserved. The system may undergo expenditure in which case the money in the bank is not isolated but is transferred somewhere else. --Damorbel (talk) 20:14, 20 November 2012 (UTC) Nope: ΔE=Q+W. All three use the same units. I do not see how these comparissions with bank accounts help, but if you receive a couple of bucks and have a million in the account they are all bucks. W=INTEGRAL(F.vdt). I think you might be confusing _force_ with _work_ Work is work, wether it is an infinitesimal ammount (δW) or the total ammount involved in a process: it has the same units. δW=F.vδt. http://en.wikipedia.org/wiki/Work_(physics) In a similar way, we have Fourier's law to model heat transfered through conduction (http://en.wikipedia.org/wiki/Thermal_conduction)or the equations for radiative heat transfer (http://en.wikipedia.org/wiki/Thermal_radiation). In all cases heat has the same units as does work and energy (ΔE=Q+W), both heat and work are functions of the path taken by the process, meanwhile energy is a function of state (i.e. kinetic energy is a function of velocity, potential energy a function of position in a force field...). Heat and work are energy being transfered. This is why the "money" example does not add up to me: it is as if some of the money that is "useful" was destroyed with each transfer and depended on the path, which is not the case: I can´t think of a proper analogy regarding money. --Crio (talk) 21:59, 20 November 2012 (UTC) Perhaps it would help if you told me what you call the energy of the vibrating particles in as system of particles when such a system has a uniform temperature and the particles are able to exchange energy freely. That wasn't addressed to me, but I'll answer: thermal energy, or internal energy, or simply energy. Heat is the transfer of that energy to another system or part of the system. Again: energy is money in the bank, heat is deposits or withdrawals (that works slightly better than salary). I've seen you question this over and over and over again, but that is in fact the way these terms are defined in physics, and there's nothing inconsistent or even particularly confusing about it other than semantic confusion with the common usage. Waleswatcher (talk) 21:17, 20 November 2012 (UTC) Waleswatcher, perhaps the question "...what [do] you call the energy of the vibrating particles... " wasn't addressed to you but neither have you answered it. Your 'answer' is that the transfer of energy is 'Heat'; my question can be rephrased as: - 'what do you call the energy before it is transferred'? In my opinion this is the energy that gives a system its temperature.--Damorbel (talk) 08:35, 21 November 2012 (UTC) Question:' what [do] you call the energy of the vibrating particles? Answer: thermal energy, or internal energy, or simply energy. Waleswatcher (talk) 11:49, 21 November 2012 (UTC) No,Waleswatcher, the question was about the energy of the vibrating particles (energy per particle) which is, through the Boltzmann constant, their temperature measured in Kelvins, Celsius etc. and thus their hotness which of course is the common interpretation of heat. Your response thermal energy, which is of course measured in Joules, depends on the number of particles in the system - NA if the system is a mole(unit), but the system can be any size you like, having energy corresponding to its size. The amount of thermal energy a system does not require it to be in equilibrium; however to know the temperature of any system there are two requirement 1/ the system must be in equilibrium and 2/ the number of particles and the total (thermal energy Q in it must be known. Average particle energy is given by the total thermal energy Q divided by the number of particles (N) in the system. So Ts = Q/NkB where Ts is the system temperature Q = thermal energy and N is the number of particles the system. --Damorbel (talk) 14:22, 21 November 2012 (UTC) You didn't specify "energy per particle". I don't know of a specific term for that other than "energy per particle". The term "heat" does not in any way or any context (technical or otherwise) describe that. In any case, since I don't see any discussion here of the article, we're done. Waleswatcher (talk) 14:33, 21 November 2012 (UTC) What I wrote (above) was Perhaps it would help if you told me what you call the energy of the vibrating particles in as system of particles. Seems there is room here for misunderstanding. The connection with the article is that 'Heat' should be measured by temperature - the long standing measure. Temperature is an intensive (local) parameter - the greater the temperature the more powerful the action. Attempts in the Heat article to characterise it as an extensive quantity (energy - joules) cannot be sustained, certainly the second law of thermodynamics would collapse! Because it contains so many inconsistencies arising from this energy in transit meme, the article has very little value, it needs extensive revision. --Damorbel (talk) 15:18, 21 November 2012 (UTC) Hi Damorbel, what you have written is of course nonsense. But that isn't really the point. The point is that your view is contrary to every reliable source on physics, thermodynamics, stat mech, etc. Therefore, it cannot go into a wiki article as per wiki policy (that all statements in articles be supported by reliable, published, secondary sources). As such, there is no point in discussing your views here any longer. Waleswatcher (talk) 20:21, 21 November 2012 (UTC) Waleswatcher is right: the internal energy of a system is related to it's temperature. One might try to isolate, from the generalized internal energy of the system, the "thermal" energy (the energy that is directly related to temperature) from "other types of energy (the energy that the system has with respect to a frame of reference regarding which it is moving, the energy the system has because of it's position in a force field, the energy contained in it's mass as E=mc2, the chemical bonding enegy in it's components, or the energy related with the weak or strong nuclear forces...) but in a generalized theory of thermdynamics it is usually not that important which "type" of energy one is talking about... --Crio (talk) 22:09, 20 November 2012 (UTC) Crio, my question is not 'related to it's temperature', it is about the energy that gives rise to the system temperature(s). My position is that the temperature(s), that is to say the heat, of a system derives directly from the microscopic kinetic energy of the particles comprising that system. --Damorbel (talk) 08:52, 21 November 2012 (UTC) Then, Darmobel, your position is _wrong_ You _are_ confussing the concept of "thermal energy" and "internal energy" with the concept of "heat", in regard to thermodynamics and physics. From a statistical mechanics point of view, the temperature, that is to say the _thermal_energy_ (not the heat), of a system derives directly from the microscopic kinetic energy of the particles comprising that system, to put it in your words. ΔU(T)=Q+W, for a given _process_ where U(T) is the internal energy of the system, composed, if you will (although this is unnecesary from a classical thermodynamics point of view) from the "thermal energy", "chemical energy", "nuclear energy", etc. of the system. These are _functions_of_state_, energy is a function of state, Temperature is a state variable. Then for a thermodynamic process that changes the internal energy of a system this change is equal to the _net_ work done on the system plus the ammount of heat transfered into the system. Heat and work are two distinct functions of path: through different paths between the initial and final states of the system different ammounts of work are done on the system _and_ different ammounts of heat are exchanged between the sorroundings and the system. Entropy is also a function of state dS(T)=δQrev/T. dS(T)>=δQ/T, ΔS(T)>=INTEGRAL(δQ/T). See: http://en.wikipedia.org/wiki/Thermal_energy Where "thermal energy" is defined as :$U_{thermal}=N\cdot f\cdot {\tfrac {1}{2}}kT.$ From a statistical mechanics point of view. There you can read " Distinction of thermal energy and heat In thermodynamics, heat must always be defined as energy in exchange between two systems, or a single system and its surroundings.[8] According to the zeroth law of thermodynamics, heat is exchanged between thermodynamic systems in thermal contact only if their temperatures are different, as this is the condition when the net exchange of thermal energy is non-zero. For the purpose of distinction, a system is defined to be enclosed by a well-characterized boundary. If heat traverses the boundary in direction into the system, the internal energy change is considered to be a positive quantity, while exiting the system, it is negative. As a process variable, heat is never a property of the system, nor is it contained within the boundary of the system.[2]" The thermal energy of a sytem _can_ be used to produce work, see: http://en.wikipedia.org/wiki/Thermal_efficiency There you will be able to see also the maximum efficiency of a thermal engine, given by Carnot's cycle. Heat (physics)is what it _is_ not what one want's it to be. It is as if I thought Ring (abstract algebra) was, somehow a ring like my wedding ring, or that the color(quantum mechanics) was actually blue. Heat _is_not_ Thermal Energy. --Crio de la Paz (talk) 00:47, 22 November 2012 (UTC) laws and principles and requirements Editor Rjstott made a well-intentioned but not well justified edit, when he changed "The first law of thermodynamics requires that the internal energy of an isolated system is conserved" to "The first law of thermodynamics describes the principle that the internal energy of an isolated system is conserved." The use of the word law to refer to generally true scientifically intended propositions about nature is in a sense allegorical or metaphorical or it may be called a trope. A principle is not the same thing as a law. A principle is a proposition from which other propositions are deduced; more than that, it is an initial proposition for a wide range of deductions. Another word that means nearly the same as principle is axiom, though these two words are usually used in different contexts. The first law of thermodynamics is sometimes called the first principle of thermodynamics, and sometimes it is called a theorem of experience. To say that it requires something is not to say it causes that thing. Editor Rjstott's well-intentioned edit seems to assume that is so to say, and this assumption is not right. It is proper to say that the first law of thermodynamics requires that the internal energy of an isolated system is conserved. It is simply poor language use to say that the first law of thermodynamics describes the principle that the internal energy of an isolated system is conserved. The first law does not describe any principle. It states something, a principle if you like. Moreover, the statement that the first law is not that the internal energy of an isolated system is conserved. The law explicitly refers to changes in the internal energy of any system that is covered by thermodynamics, and is thus more general than the statement about isolated systems. The phrase 'describes the principle' is pleonastic; that is to say, it says the same thing twice over in a way that does not add to the meaning; it is faulty language usage. But it is true that the law includes as one of its essential implications that the internal energy of an isolated system is conserved. The word requires here means the same as 'includes as one of its essential implications'. This is ordinary language usage, consistent with the semantics of the word law in this context, as a metaphor, and is appropriate here. It is very good that editor Rjstott should be alert for matters of language, but on this occasion he acted too enthusiastically.Chjoaygame (talk) 02:12, 18 November 2012 (UTC) I undid your reversal of Rjstott's contribution. I think the vast number of words you needed to explain your point is more than sufficient to show you have not got one. --Damorbel (talk) 07:49, 18 November 2012 (UTC) Damorbel, this utterly unjustified undo of yours is most naturally, in view of current activity here, read as a mere personal attack on me. You have been doing this kind of thing for some time now, but I have not pointed to it till now because such things are hard to demonstrate unequivocally, or would need too much time and effort to demonstrate, and because I have not wanted to encourage your predatory and irrational editing behaviour by responding to it. This one seems unequivocally clear. Your "justification" just above makes no reference to the issues at stake, and has no weight as rational argument. Many words are needed to explain subtle abstract ideas to novices. If I write a careful justification for my action, you attack me for wordiness. If I do not, you attack me for lack of detail. You seem to have lost the plot. I will not respond by undoing your undo because such a response would only reward your inordinate appetite for irrational and destructive edit conflict, which you continue to try to arouse.Chjoaygame (talk) 08:51, 18 November 2012 (UTC) Laws simply STATE relationships. So simply state what this one states. Simplify! SBHarris 09:19, 18 November 2012 (UTC) SBHarris' compromise, that "the law states" may be acceptable, but is not as precise as the previous version, that "the law requires". The law states more than this requirement, and this is signalled by the word 'requires', which is perfectly good English. His appeal to simplicity seems to be motivated by a desire to compromise. And the compromise reduces the explicit specificity of the article entry, for no reason that I can see other than to appease Damorbel, and perhaps editor Rjstott, whose English fairly deserved censure.Chjoaygame (talk) 10:03, 18 November 2012 (UTC) Sbharris has it right. --Damorbel (talk) 09:28, 18 November 2012 (UTC) Damorbel makes no response to my observing that his undo is most naturally read as a mere personal attack on me. If Damorbel really thought for himself that the edit of SBHarris was appropriate, why didn't he make it himself when it was called for?Chjoaygame (talk) 10:03, 18 November 2012 (UTC) This is called "fiddling while the article burns!". Chjoaygame, it is far more important that an encyclopedia article should recognise that any article on heat should fully explain why the theory of heat is about the energy of particles - which is absolutely not the case at present. I find it quite bizarre that the present article does not show the proper relationship between the system energy, the number of particles in the system, its entropy and the role of temperature. Please stop going on about your personal feelings and get involved with the physics of heat - please! --Damorbel (talk) 12:03, 18 November 2012 (UTC) Damorbel was so keen to attack me that he was blind that his edit, solely of a grammatical nature, was restoring a faulty pleonasm, "the law describes the principle". Then, blind that a personal attack of the kind he made is unethical here, he suggests that it is my feelings that are the problem here. Dear Damorbel, you flatter yourself to suggest that your personal attack on me might have affected my feelings, no, it seemed a joke to me, that you would so demean yourself. But it is right that I should point out that your action is unethical. You ask to focus on the physics, but your edit was merely grammatical, and mistaken at that. It is you who is burning the article, still blind to your personal attack on me, blind because of your above noted mental block. You have lost the plot.Chjoaygame (talk) 13:30, 18 November 2012 (UTC) Damorbel seems to have a persistent confusion bewteen the concepts of temperature, "thermal" energy or, in a more general fashion, internal energy, and heat. He seems to think that "heat" is "internal energy" and that is _not_ the definition in physics: heat is not temperature, heat is the phenomena that occurs when two systems with different temperatures are in thermodynamic contact: heat flows from the hotter body to the colder body. A gradient in temperature is the "cause" of heat being exchanged, it is not the "heat" being exchanged. The energy contained within a system (internal energy) is not "heat". "Heat" is a function of path. Energy a function of state. In classical thermodynamics temperature is not defined in terms of particles. In statistical mechanics the concept is linked, succesfully, with the behavior of the atomic structure of matter. --Crio (talk) 22:26, 20 November 2012 (UTC) The reading of http://en.wikipedia.org/wiki/Calorimetry could prove--Crio (talk) 22:30, 20 November 2012 (UTC) interesting. Crio you are missing my point entirely by introducing into the argument, when you write "heat is ... when two systems with different temperatures are in .... contact:" a matter with has nothing to do with my point, because your system, having two (or more) temperatures, is not in thermal equilibrium. Thus, according to the 2nd law of thermodynamics, there is a transfer of energy in your system. My question has nothing to do with the transfer of energy since it applies equally well to a system in equilibrium. All I want to know is, what the energy (if you think it exists at all) is called that makes the system hot i.e. gives a system its temperature(s), makes it above zero K, etc. etc. --Damorbel (talk) 09:21, 21 November 2012 (UTC) Actually "hot" implies with respect to what?. Internal energy is a function of T: the internal energy of a system is related to it's temperature. In a more specific way "thermal energy" even when it is difficult to stablish what part of internal energy is "thermal" in nature and what is not. This involves studying the internal structure of the system or dedifining the system. See: http://en.wikipedia.org/wiki/Thermal_energy "Thermal energy is the part of the total internal energy of a thermodynamic system or sample of matter that results in the system temperature.[1] This quantity may be difficult to determine or even meaningless unless the system has attained its temperature only through heating, and not been subjected to work input or output, or any other energy-changing processes. " Now this is _not_ a matter of what "I think" or "Darmobel thinks" it is a matter of how quantities _are_ defined in physics, and, in this case, in thermodynamics. Classical thermodynamics defines a system and it's sorroundings, it does not study the internal structure of the system. Statistical mechanics is a mechanistic science that is compatible with classical thermodynamics and that studies how the atomic structure of matter is compatible with classical thermodynamics. but "heat(physics)" is still a transfer phenomena, not a state function. Temperature is a state variable and internal energy is a state function. I think Darmobel is confussing "heat(physics)" with "thermal energy" "internal energy" and "temperature". That is where his confussion arises whe writing about the general theory of classical thermodynamics, which he seems to think reduced to one of it's mechanistical interpretations (statistical mechanics). Classical thermodynamics theory seems to be compatible with other theories as well, including a generalized theory of gravitation (general relativity) and information physicis, even though not all of these theories have been unified as of yet. The basic concepts that prevail with the basic laws of thermodynamics seem to be a set of rules for all procecess, disregaring it's internal mechanics (how work and heat are computed as functions of path), up until now. That is what is so interesting about thermodynamic theory (classical), specially since it was born out of an analysis of "heat engines". Chjoaygame is _right_ when he mentions that the problem is regarding heat(physics,thermodynamics) and a common language use of the word "heat". This is similar with regard to a generalized concept of the word "work" (I shoud be doing some "work" right now instead of writing on the wiki). Or action, or force, or anyother quantity that has a specific meaning in physics. It is similar to what happens in mathematics when you talk of a "field" or a "group" or a "ring" or a "set" or a "lattice"). And it is true that, when one goes into "engineering topics" one stops using the most rigorous definitions if they are not "useful" to solve an engineering problem. --Crio de la Paz (talk) 17:02, 21 November 2012 (UTC) difference between physics and the discipline of heat transfer about the idea of "convection of heat" The Wikipedia article on transfer of heat says that it is concerned with a discipline of thermal engineering, concerned with thermal energy. It classifies heat transfer mechanisms as conduction, radiation, and convection. It also admits the engineering idea that a mass transfer can comprise an associated heat transfer. In this engineering terminology, sometimes mass transfer might refer to transfer of mass by diffusion between open systems, but very often it refers simply to motion of a body of fluid, considered as a mass transfer as a body moving from place to place rather than as diffusion between open systems. This thermal engineering terminology differs from that of physics. In physics, the energy associated with mass transfer by motion of a body from place to place is represented by kinetic energy of bulk movement, by potential energy with respect to long-range external forces such as gravity, and by internal energy belonging to the body considered without regard to its motion from place to place. In physics mass transfer on a microscopic scale, known as diffusion, can occur between open systems, but not between closed systems. In physics, transfer of energy as heat is defined for transfer between closed systems, but is not defined in general for transfer between open systems.(Münster, A., 1970, Classical Thermodynamics, translated by E.S. Halberstadt, Wiley–Interscience, London, ISBN 0-471-62430-6, pp. 50–51. Kittel, C. Kroemer, H. (1980). Thermal Physics, second edition, W.H. Freeman, San Francisco, ISBN 0-7167-1088-9, p. 227. Reif, F. (1965). Fundamentals of Statistical and Thermal Physics, McGraw-Hill Book Company, New York. Carathéodory, C. (1909), Untersuchungen über die Grundlagen der Thermodynamik, Mathematische Annalen, 67: 355–386 doi=10.1007/BF01450409. A partly reliable translation is to be found at Kestin, J. (1976). The Second Law of Thermodynamics, Dowden, Hutchinson & Ross, Stroudsburg PA.) It follows that in physics, mass transfer by diffusion can be associated with transfer of internal energy, but not with a uniquely defined quantity of energy transferred as heat. In physics, there are several well recognized extensive variables of state that represent well defined quantities of energy that belong to a body: internal energy, Helmholtz free energy, enthalpy, Gibbs free energy. These represent quantities of energy that, besides being state variables belonging to a body that can move with its bulk motion, can also be transferred between bodies, including transfers by diffusion. The thermal engineering term 'thermal energy' is loosely defined and may perhaps loosely refer to one or all of these quantities, but, unlike in thermal engineering, in physics the phrase 'thermal energy' is not recognized as an extensive state variable that represents a well defined quantity of energy that belongs to a body. Likewise, in physics, heat is not an extensive state variable of a body; heat is always energy in a process of transfer. In physics, one can consider convection of internal energy, Helmholtz free energy, enthalpy, Gibbs free energy, and indeed also of convection of entropy. This is because convection means transfer by bulk motion of a quantity that is indicated by an extensive state variable of a body of fluid. From this, it follows that, differing from thermal engineering, physics speaks of convection neither of thermal energy nor of heat. In physics, heat transfer is by conduction and radiation.Chjoaygame (talk) 06:01, 21 November 2012 (UTC) Response by Damorbel Chjoaygame you write "This thermal engineering terminology differs from that of physics." Interesting. But what makes you think engineers are somehow constrained in the language they use? Engineers somtimes need to describe complex system built up of already complex subsystems. For a time I was responsible for the power subsystem of a communications satellite, to do my job I needed to understand the thermal control of the satellite, the design of the solar arrays, the orbit of the satellite, the control and regulation and storage of on board power and much, much more. To handle this massive comunications problem engineers use a restricted set of terms that frequently summarise the physics involved i.e. they don't go back to basics on every occasion, it would waste far too much time. An unfortunate side effect is that this obscurity, unless one is up to date with the functioning of the new design, one will be effectively excluded from discussions. I did not actually design these various aspects but I needed to be able to talk to those who were in a meaningful way, otherwise I would have been speedily shown the door. In my job I learned a lot and I taught my colleagues a lot, that meant that, on occasions, I had to correct some of my ideas. Good engineering practice requires that designs are tested to see if they perform as predicted; in this way the validity of the communications is finally checked. In physics the problem is quite different. Theories in physical science, (unlike mathematics) come and go, think of phlogiston and caloric. Physicists (should) want their work to be understood as widely as possible so they should use terminology that is not only widely understood but self consistent. This last requirement is generally upset when improved theories emerge, for many physicists it is almost impossible to accept changes to the ideas of their youth, a good example is Joseph Priestly who carried the idea of heat as a substance phlogiston to his grave, he would not accept the new idea of caloric. In turn Sir Humphry Davy and members of the Royal Society actively suppressed the new kinetic theory of heat (with energetic particles) as expounded by John Herapath, in 1821, and again by John Waterston in 1843; you can read about this here. This is a good example of the importance of scientific experiment, a hypothesis must be tested. Sir Humphry and other members of the Royal Society did not test the new theory, they rejected it out of hand as ridiculous. Not all physics can be tested in a laboratory but there must be some evidence of its validity that is availble to all; being available to all requires a universal terminology, very different from engineers who do not rely on terminology for success. --Damorbel (talk) 07:32, 21 November 2012 (UTC) Response by Crio de la paz This page should be about how "heat" should be dealt with on the wiki, not "a contest of wills"; and it should not be a contest between "engineering" and "physics". There _is_ an specific notion of _heat_ in _physics_thermodynamics_ that is fundamental to all of physics and it's applications. In engineering one deals with "heat transfer" phenomena and equipment design and uses thermodynamics, transfer phenomena theory, dimensional analysis, empirical data that has not been well modeled mechanistically, "rules of thumb" and whatever is handy to solve engineering procecess. Thermodynamic analysis (in it's classical, general form) has been one of the most fundamental aspects of how the world we live in is described: it has hold true where Newton's laws of motion haven't (and others). In "chemical engineering" "modeling of procecess" first a system is defined, then the fundamental conservation laws that apply are stated, including the second law of thermodynamics (which is not a conservation law but the law that governs the increase of entropy of the universe in most procecess). Then the constitutive realationships and parameters that are going to be used are introduced to solve for the model in question. The laws of conservation of mass, momentum, angular momentum, charge, energy, the second law of thermodynamics they are regarded as fundamental laws, not constitutive relationships (as are most physical "laws"). In "heat transfer" one deals with transport phenomena related to the subject matter and desing of equipment (heat exchangers, evaporators, cooling towers, boilers, furnaces, jacketed vessels, etc.)--Crio de la Paz (talk) 17:28, 21 November 2012 (UTC) Response by SBHarris Perhaps we can simplify this some. The article itself says that heat is a process of energy flow down a thermal gradient, as the result of the thermal interaction. That means that only diffusion and radiation count as pure forms of heat which fit the simple definition. Everything else which results in a "net" flow of heat from A to B, has some tricky step "in between" where heat is not being transfered (by the above definition) but rather internal energy is transferred without heat flow. The simplest example is a "heat pump" which is a beloved engineering term. But by definition one cannot pump heat against a thermal gradient, which is what heat pumps are supposed to do (that's what the name says, right?). Thus, actually it is internal energy that is pumped up the temperature gradient, not heat. At either end of this process, heat indeed flows down a thermal gradient in the normal way. The heat energy just finds that at its new home, it is in a place where it would not have gotten to on its own, in a single step or by any series of purely thermal interactions. Now, consider convection (free or forced). In the intermediate step, a fluid "advects" (carries) energy from one place to another, like water carrying silt down a river. But does the fluid here carry "heat"? Not by the definition in this article, and not even by the definition of most engineers. When you carry a cup of hot coffee from one end of the room to the other end, not letting it cool at all, would an engineer say that you're carrying "heat"? Even engineers who believe loosely in thermal energy would not say you're carrying "heat" but would say you're carrying thermal energy. We prefer "internal energy". Heat is when something hot transfers energy to something cold, not when when some peice of mass at the same temperature is moved mechanically and grossly from here to there, not changing temperature while it changes position. Likewise, an engineer would not say that a (perfectly insulated) pipe carrying hot water was carrying heat, if (again) the temperature was constant over the length and there was no heat exchange. When heat transfer happens at either end of such a pipe, then at those places, heat appears. The entire process is lumped by engineers into "(forced) convective heat transfer," but actually the only heat transfer happens at either "end" of the mass flow, and doesn't happen in between (or doesn't NEED to). And when this heating process (true and simple heat transfer) DOES happen, it happens by good-old-fashioned thermal diffusion. Down a thermal gradient. So convection is also like a heat pump-- there is heat at the ends, going in an coming out, but in between, there is none. It's like money wire transfer-- I take bills into one bank and across the country some minutes later, somebody else takes bills out. That's not bill transfer-- it just looks like it. For all intents and purposes it could be (and an engineer might be satisfied). But mechanistically, it isn't. It's money transfer, not paper currency transfer. Don't be fooled. SBHarris 01:31, 22 November 2012 (UTC) Response by Crio SBharris: Actually a "heat pump" is a thermodynamic cycle. It involves (as most usual) four steps. i.e. the fluid is compressed, it then releases _heat_. The fluid then goes through an expansionary valve (or a capillary tube, or a turbine) that lowers it pressure. Then it absorbs _heat_ from it's sorroundigs and goes again into the compressor. In an idealized system heat is absorbed from the environment on one side and heat is realeased on the environment on the other side. Work is done in the compressor and some work might be extracted on the turbine. The thing here is that _heat_ is that which is transfered at both ends. See: http://en.wikipedia.org/wiki/Thermodynamic_cycle http://en.wikipedia.org/wiki/Temperature-entropy_diagram There you can see how thermodynamic cycles are calculated. But now I realize we agree: heat is transfered _at_both_ends_ (in an idealized system, in a real system the compressor also releases heat, etc.) not "in between" in between we are changing the _state_ of the fluid. Convection is a more complicated subject as you can see in: http://en.wikipedia.org/wiki/Convection "Convective heat transfer is one of the major modes of heat transfer and convection is also a major mode ofmass transfer in fluids. Convective heat and mass transfer take place through both diffusion – the randomBrownian motion of individual particles in the fluid – and by advection, in which matter or heat is transported by the larger-scale motion of currents in the fluid. In the context of heat and mass transfer, the term "convection" is used to refer to the sum of advective and diffusive transfer.[1] " Of course it all depends on the system being analyzed and wether you are establishing a "volume control" or a "mass control" for the system in order to establish your conservation laws for the ssytem. Since the system might not be "closed" depending on the definiton of the system, when doing an energy balance on the system you have to take into account the energy brought into the volume of control by mass that enters the system and mass that leaves the system, in your energy balance. And of course, if one tries to model turbulent flow of compressible fluids one might run into situations where Navier Stokes prove unsolvable and only empirical approaches are "doable". --Crio de la Paz (talk) 03:17, 22 November 2012 (UTC) response by SBHarris To Crio: thanks, I know how a modern heat pump works. The point is how a minimal heat pump works. Without the gizmos. You don't need phase changes-- they only increase efficiency. And you don't need convection-- if you do it slowly you won't get enough to count. To make a refrigerator for your house, take a cylinder of air (or any gas) outside into the hot day, and compress it until it's higher temp than the hot environment. Let the heat bleed out by conduction. Carry it indoors and let it expand against as much pressure as possible, slowly reversibly. If you've compressed it enough outside, it will cool inside to lower than room temp. Let heat flow in by diffusion. Then carry it outside and repeat. It's not a great refrigerator, but (absent your body heat) it will cool the room. The heat-equivalent of the work you do, will be ejected outside, plus whatever heat is absorbed inside. To pump heat the other way from cold outside to warm inside, simply reverse the cycle with compression phase inside, and expansion outside. Now, when I'm carrying the cylinder of gas inside to outside and vice, versa, do you think I'm moving heat? I'm not. No entropy change is involved in me moving a cylinder of gas. Entropy changes only when heat diffuses into or out of the cylinder. In fact, that's how we know it's heat: a bit of heat flow δQ is always TdS. But dS is zero when I advect, as it's reversible.SBHarris 05:05, 22 November 2012 (UTC) Respose by Crio SBHarris: Actually when there is passive difussion there is an increase in entropy, see: http://www.rsc.org/learn-chemistry/content/filerepository/CMP/00/001/061/Why%20passive%20transport%20happens%20entropy.pdf?v=1352425760476 For a TS diagram of a heat pump figure 2 in http://en.wikipedia.org/wiki/Heat_pump_and_refrigeration_cycle is quite a good example. For a TS diagram of Carnot cycle see: http://en.wikipedia.org/wiki/Carnot_cycle Figure 2. Specially http://en.wikipedia.org/wiki/File:Carnot_Cycle2.png is of interest. The Carnot cycle is _the_most_eficient_ thermodynamic process between to different temperatures, where work is done isentropically and heat is released isothermally. Actually the example of you moving a cylinder of has is flawed: it is _quite_ inefficient ;-) and it is not reversible (you need to expend a lot of work in doing so: it is not reversible, it does not happen spontaneously). Advection and convection are not reversible, quite the contrary: they tend to be quite irreversible process: when a mass of fluid is heated up by a hot surface it rises. But it will not lower itself heating the surface back without external work. I forced convection one is _introducing_ an external force into the system in order to perform work in order to do process that _are_ irreversible. A reversible process is that which occurs spontaneously. Cheers!--186.32.17.47 (talk) 19:02, 22 November 2012 (UTC) I have moved the immediately forgoing to this point in the page because it seems that this is its home. I hope this is right. Whatever. A reversible process is a theoretical idealization, and cannot occur in nature; it can be closely approximated by a slow enough process, but not exactly realized in a finite time. Spontaneous processes, the only ones that occur in nature, are always irreversible. This is fundamental thermodynamics.Chjoaygame (talk) 04:32, 23 November 2012 (UTC) Response by Waleswatcher There is very little physical distinction between radiative heat transfer - where a flow of photons carries energy from a hot to cold body - and convective heat transfer - where a flow of molecules carries energy from a hot to cold body (or for that matter conduction, where a flow of phonons carries energy from a hot to cold body or part of the body). I'm not opposed to differentiating them in the article, but we have to be careful asserting that one is more "direct" or "fundamental" than the other. Such statements need to be referenced. Waleswatcher (talk) 03:16, 22 November 2012 (UTC) response by Crio de la paz Waleswatcher has a point, though photons have zero rest mass... that ought to be a difference... --Crio de la Paz (talk) 03:29, 22 November 2012 (UTC) Another thing: most probably what will happen in most "heat pumps" at "both ends" would not be "thermal difussion" or "conduction" but "convection". Cheers!--Crio de la Paz (talk) 03:31, 22 November 2012 (UTC) Walesatcher: why is heat transfered "indirectly" in convection? I do not understand the term "indirectly" aplied in this context. Thnks! --Crio de la Paz (talk) 03:42, 22 November 2012 (UTC) Phonons typically also have a mass, so rest mass doesn't distinguish convection from conduction. Also I'm not sure why it's important in this context. The term "indirectly" isn't very good, it was a compromise to try to preserve the sense that convection is somehow less fundamental, as was written there by another editor. I'd prefer to remove it and go back to what I had originally. Waleswatcher (talk) 13:09, 22 November 2012 (UTC) Phonons typically also have a mass. They do? Never heard of it. Phonons are the mechanical equivalent of photons i.e. they derive their properties from wave motion in a mechanical lattice, but the massive particles in the lattice are not transferred. What is transferred, as with photons, is momentum. Have you got an explanation, or better still, a link? --Damorbel (talk) 14:58, 22 November 2012 (UTC) So called "optical" phonons, for example, or any other where omega doesn't go to zero with k. Waleswatcher (talk) 05:22, 23 November 2012 (UTC) response by SBHarris To Waleswatcher, you've missed the fundamental property of heat, which is that as it flows, the entropy of the system increases due to the heat flow. But there is no entropy increase when I move a hot object from here to there. Or a hot stream of fluid from here to there. That part of the "convection" scheme, the purely "advective" part, involves no entropy changes. That is because heat is not being moved. ENERGY is being moved. Do you see? Photons radiated from a hot object expand into a larger volume; entropy goes up. The same when a gas expands, even isothermally. And of course, always in all heat conduction processes, as those little phonons multiply and occupy more states. The system occupies more of phase space. But again, pure advection of hot things does not push phase space. It's (obviously) reversible. If I can move a hot object THERE, I can just as easily move it BACK. Try putting those photons that radiated from a hot object back where they came from, or the phonons conducted away for that matter. You'll pay for it in entropy cost, if you do. Ditto for everything else that has to do with REAL heat transfer. SBHarris 05:05, 22 November 2012 (UTC) That's not the case. Convection - at least when it occurs as a result of heating of a gas, as we are discussing here - is a spontaneous process that is always associated with an increase in entropy. You cannot separate the "advection" part from the "heat" part in this context (which is rather the point). Advection is simply the motion of a lot of molecules, gas in this case; if that motion carries hot gas molecules into a region occupied by cold gas molecules, the entropy of course increases even in the absence of any molecular collisions. As you say, try putting the hot molecules back in the corner where they came from after advection has carried them into and a region of cold molecules. Waleswatcher (talk) 13:13, 22 November 2012 (UTC) In the absence of diffusive energy transfer (which would be better approximated in free convection in a viscous fluid like heavy oil), you could partly reverse it, simply by turning the system over, so that buoyancy forces put the plume back where it was. In high viscosity systems where diffusion is limited, very strange and odd-looking reversible things like that, actually happen. Have you seen the demo with the blob of colored fluid that starts in the thin space between two counter rotating concentric cylinders? You rotate them, and the color smears out and you think entropy has gone up a lot. Wrong, because when you turn it backwards the blob puts itself back together! Surprising degree of reversibility there is due to relatively little entropy of diffusion. You say "even in the absence of molecular collisions", then specify a *gas*, where all the irreversibility happens for precisely that reason! In any case my example of forced convection where these two parts of convection (advection and diffusion) CAN be separated, demonstrates the truth of my point. Purely advected heat is not actually heat. Throwing a hot object is not "heat transfer". That's just silly. SBHarris 16:29, 22 November 2012 (UTC) I am very familiar with that demo - but its relevance to this discussion is close to zero. Yes, it's possible to have advection that is approximately reversible, and I never claimed otherwise. But when flows of particles occur because of heating, that is never the case. You say "even in the absence of molecular collisions", then specify a *gas*, where all the irreversibility happens for precisely that reason! Sorry, but that's simply wrong. For example, the free expansion of a gas is irreversible and generates entropy even with no molecular collisions whatsoever. Purely advected heat is not actually heat. I have no idea what you mean by that. Look - take a high temperature object and put it into a cold enclosure. If the enclosure is completely empty initially, the object will radiate photons, filling the container with a gas of photons that will eventually equilibrate with the object. During the equilibration, there will be convection in the photon gas (let's say the container is very large, so it takes significant time for the photons to cross it) as photons flow out from the object, but not - at least initially - back into it. In that instance, convection and radiation are identical If the enclosure is full of a cold gas - photonic or molecular - there will again be convection of gas particles as the hot particles near the object expand outwards. If the enclosure is full of solid, there will be convection of phonons. In that case, conduction and convection are identical. If a hot gas and a cold gas are brought into contact, there will be a net flow from hot to cold initially, because the hot gas diffuses faster. etc. etc. The point is, convection is an important and fundamental mechanism of heat transfer, and is described as such in multiple reliable sources. Until and unless anyone finds a reliable source that explicitly states that convection is not heat or some such, the article should not imply it. A source not mentioning convection does not indicate anything of the kind, and interpreting as such is in contravention of wiki policy (it's unjustified synthesis and/or original research). I'm perfectly happy for the article to explain the usage and differences between convection, conduction, and radiation - that's a good idea - but I do not agree that it should ignore convection or treat it as if only ignorant engineers regard it as a form of heat. Waleswatcher (talk) 00:35, 23 November 2012 (UTC) What you term convection of photons (or EM radiation classically) is diffusion. Diffusion needs a concentration gradient. That can be mass per volume or energy per volume. Entropy goes up in either case and I never said otherwise. But entropy does not go up in advection, which doesn't involve concentration driven processes or increases in volume. Advection just means carrying along. When I move a thermos of hot coffee from my desk to yours, that's advection. Advection of caffeine, for instance (mass transfer). Advection of energy (internal energy transfer). But unless I open the thermos and allow energy out, there is no HEAT transfer. There is no change in entropy. It is reversible. I have not moved (transferred) heat, because there is no heat! Can you find the heat? So, do you now understand my meaning, when I say that pure advection of heat is an oxymoron? Heat cannot advect by definition. It can only diffuse, and radiative transfer is only a type of diffusion. Whether one-way or two-way makes no difference. The point is that entropy increases more in one direction than it decreases in the other. But there is always a change, in diffusion. SBHarris 23:25, 23 November 2012 (UTC) Diffusion needs a concentration gradient. That can be mass per volume or energy per volume. Entropy goes up in either case and I never said otherwise. Actually, yes you did - you said that molecular collisions are the only source of irreversibility in a gas. That's wrong. Diffusion, or simply free expansion, or convection, all increase the entropy and are irreversible, and all can happen in the absence of any molecular collisions whatsoever. As for advection, I didn't term anything "advection" or use it anywhere in the article - that's a term that you introduced into the discussion. The term I used is "convection". In standard usage, "convection" includes diffusion from a heat source. So if you agree that diffusion is a form of heat or heat transfer, then unless you have a different definition of convection than the standard one, it sounds like you agree with the text of the article as it is now. In that case, we are done here. Waleswatcher (talk) 00:12, 24 November 2012 (UTC) Convection is advection plus diffusion. I brought in the word because it's a simple way to separate out the physical processes in convection where heat transfer happens, from those where it does not. Heat is transferred by diffusion not by advection. All the heat transfer in convection is by diffusion, so why confuse the issue for the poor reader that takes this article at its word that heat cannot "reside" in materials and thus clearly cannot be transferred by material motion. The last being essential for the idea of convection as some kind of process in heat transfer differentiable from diffusion , no? I've sorry that you apparently had some volume-expanding process in mind as part of what makes convective heat flow irreversible. I didn't visualize your model. Gas expands as it rises but in an adiabatic system it also is compresses when it sinks. That is the cause of the lapse rare in the atmosphere. It means a parcel of air can rise or fall reversibly and pure temperature differences cause no convection unless temperature gradient exceeds this lapse. Adiabatic expansion is reversible as entropy doesn't change. in any case what do we tell the reader who wants to know if hot water flowing along an insulated pipe is "heat transfer"? An engineer, thinking very loosely, would say yes. A thermodynamicist clearly "no". By this article's definitions, no. But that's a textbook case of forced convection of "heat". Since most texts make no distinction between "thermal energy in motion" and heat. This article would rather not talk about thermal energy and it's easy to see why. SBHarris 01:38, 24 November 2012 (UTC) A more common and familiar case of convection is hot air rising or being blown from a vent or space heater. That is a form of heat transfer, both because the hot air diffuses into the surrounding cold air, but also because (at least if it's blown by a fan) there's an bulk flow that carries hot air some distance. After it arrives, it diffuses... except that diffusion happens all along the flow, and cannot be separated in any clear way from the flow itself. And in some cases, the flow itself is diffusion. For these reasons, convection can't really be split into diffusion+advection, nor does diffusion as a term really suffice to describe it. I'm perfectly happy describing all of this in more detail in the body of the article, but for the lead, I think the word "convection" suffices - and that's why in many reliable sources, convection, radiation, and conduction are described as the three primary mechanisms of heat transfer. Waleswatcher (talk) 02:46, 24 November 2012 (UTC) A valuable comment by true hot air expert!Chjoaygame (talk) 07:25, 24 November 2012 (UTC) I fail to understand your approach. In science when we have two simultaneous effects we cannot disentangle, normally we look for a controlled situation where one or the other is minimized so we can tell what each one by itself is doing, We do that all the time to separate out separate contributions of radiative and diffusive heat transport for example. We don't just throw up our hands and say "Oh dear me, they happen together so I can't tell what each one contributes!" There are many convection problems where advection can be nearly separated from diffusion, as in an auto radiator , and in those cases it's obvious that the advection phase does not transport heat as we define heat in this article. It follows logically that if heat cannot be stored in constant temp objects, that heat cannot be advected or convected (except as diffusion). If you don't like that, then change the definition given here! It gets even worse with energy transport systems constructed so you do without heat transport at all. When you compress a gas adiabatically to make it warmer, do you produce heat? Not according to this article, as δq= 0. When you conduct (or simply carry) that hot gas outside and allow it to do adiabatic work on the environment, even work that increases the environment's temperature indirectly (like turning a paddle wheel that heats water by friction), is heat involved? No, according to this article's definition. So, does this entire chain of events transfer heat? No. Heat is never seen here. Just because you have a hot gas at some point does not mean you have heat, or ever had heat. With no thermal gradients, no entropy change, no thermal diffusion, there never exists heat. Only advected internal energy. SBHarris 18:29, 24 November 2012 (UTC) It follows logically that if heat cannot be stored in constant temp objects, that heat cannot be advected or convected (except as diffusion) Again, it appears you acknowledge that heat can be convected. If so, we can finish this discussion, which doesn't seem to be aimed at improving the article. Waleswatcher (talk) 18:54, 24 November 2012 (UTC) The article would be improved by pointing out that heat "convection" is only heat diffusion, and that any extra energy transported by convection is not transported as heat but rather as internal energy, which is not the same thing. Further, you're probably the only editor here who does not agree with this point of view (though I don't know about clueless DamὊorbel), so you are outvoted. SBHarris 19:18, 24 November 2012 (UTC) If you can find a reliable source that says that, go ahead and add it (not to the lead, it's too detailed for that). Waleswatcher (talk) 19:20, 24 November 2012 (UTC) I see you've come back and edited your comment. First, off, "outvoted"? Huh? That's (a) not how wiki works, (b) there's been no such vote, (c) Crio de la paz has listed convection along with radiation and conduction as one of three mechanisms - so that's three editors to two, I guess (although I don't know, see (d)), and (d) I have no idea what you even believe any more. You've acknowledged that convection is indeed a mechanism of heat transfer. It's just that you (erroneously, I think) believe there's a clear and useful distinction between the diffusive and advective parts of convection. As I said, in accord with wiki policy, if you can find a reliable source that supports your view - whatever it is - feel free to edit it in. Meanwhile, we have tons of sources that list convection as one of the primary mechanisms for heat, so it's staying in the article like that. Waleswatcher (talk) 23:36, 24 November 2012 (UTC) response by Chjoaygame Perhaps very little difference, but still significant. The energy that is carried by convection is carried partly and importantly through the cooperation of the particles including their mutual potential energy, whereas for the most part, energy carried by a photon is the sole property of the photon. Also, convection is mainly one-way. One can have convection that is entirely one way. But radiative transfer is essentially two-way. This is because of the Helmholtz reciprocity principle. The heat transfer is the difference between the two ways. Photons carry energy from a source body constituent directly to a target body constituent, in one step. Convection essentially involves many particles on the way.Chjoaygame (talk) 05:31, 22 November 2012 (UTC) response by SBHarris §  Photons and diffusion, transfer heat only one way, if the cold reservoir is at zero K. The two way thing is not necessary, nor is potential interaction in a fluid, which would work just as well with an ideal gas. Nor is forced convection needed if you stop diffusion aka heating by use of an insulated thin pipe. Take a partitioned cubical container with warm gas in the lower level and cold in the upper. Or separate containers, for that matter. Make sure pressures are equal or else you'd get flow even in 0 g and it wouldn't be free convection type flow, but forced by non buoyancy pressures. Connect the spaces with a thin insulated vertical pipe. Warm gas now moves up the pipe. Before it hits the end of the pipe, is there "heat transfer" by free convection of gas? No! At any point before diffusion of heat happens you can just turn the whole assembly over and it will all go back to initial state. It's reversible. Entropy didn't increase. Energy flowed but heat did not. SBHarris 17:47, 22 November 2012 (UTC) Talking about processes with a cold reservoir at zero K !! Surely you are clutching at straws !! In the history of the discovery of the Stefan-Boltzmann law, it was recognized that the law had to be tested by formulas of the form 'heat transfer = function of T1  −   function of T2. The Helmholtz reciprocity principle of 1847 points out that if radiation can pass from A to B, then it can pass with the same attenuation from B to A. This means that heat transfer by radiation is essentially two-way, the actual heat transferred being the difference between the two ways. In a sense, you are acknowledging this by asking that the cold reservoir have a temperature that you prescribe, even if your prescription is rather demanding. In an ideal gas the molecules interact by colliding. That is an idealized kind of interaction, because it restricts the interaction to the collisions, requiring it to be zero in between collisions. When you point to forced convection as an example of one-way transfer, you are agreeing with what I am saying. That convection is different from radiation in this way.Chjoaygame (talk) 19:39, 22 November 2012 (UTC) I didn't really want to discuss radiative transfer of energy from a cold to a hot object because strictly speaking this subprocess isn't heating since by definition heat doesn't flow against temperature gradients. You cannot break this down without losing the meaning of the macro process of heat transfer that must refer to the sum of this interaction, or nothing. Break down a process into its various parts, some of which increase entropy and some of which decrease it , and you have passes into a subrealm where heat is no longer a useful concept. Heat is what happens overall. SBHarris 23:45, 23 November 2012 (UTC) response by Waleswatcher §  I'm not saying the difference isn't significant. I'm saying they are equally valid mechanisms of heat transfer on more or less the same basic footing. I suppose in some vague sense photons are more fundamental than molecules, but by the same token they are more fundamental than phonons too. And in the real world, all three are more or less equally common in people's experience. So for explaining heat on wikipedia, it makes no sense to exclude convection. Waleswatcher (talk) Dear Waleswatcher, you are making it up off the top of your head as you go along, or perhaps I should say spinning it as you go along. We are not seeking to exclude convection, as you allege. We are just pointing out that it has a status different in physics from that of the primary pair, conduction and radiation. As I have noted above, and as you have ignored, your chosen sources for the definition of transfer of energy as heat, Kittel & Kroemer, and Reif, do not actually mention convection of heat in those exact words; Reif does not mention it at all. As is your habit, you are seeking to hide this basic point of physics.Chjoaygame (talk) 19:49, 22 November 2012 (UTC) response by Damorbel §  If progress is to made in this article it is necessary to be pedantic about language. Chjoaygame you write The heat transfer is the difference.... Isn't it energy, the conserved quantity, that is transferred? With 'heat transfer' surely we are back in the days of caloric. --Damorbel (talk) 11:06, 22 November 2012 (UTC) Boltzmann constant Can anybody tell me why the Heat article does not mention of the Boltzmann constant? --Damorbel (talk) 21:44, 21 November 2012 (UTC) Yes, the reason is that instead of putting your heart's desire into the right place in the article, you have frittered your efforts into sabotaging the efforts of others in other parts of the article. No one would have hindered you from putting it in the right place.Chjoaygame (talk) 23:50, 21 November 2012 (UTC) Frankly I don't know what we'd do with kB in this article (or R = N kB, either). These constants don't have anything to do with heat. R and kB act as the simple proportionality constants, that arise because we need constants to mediate between the (arbitrarily produced) kinetic energy and temperature scales that we happen to have independently developed, and that we want to continue to use (thus requiring conversion factors between them). But neither energy or temperature is heat. SBHarris 01:06, 22 November 2012 (UTC) "These constants don't have anything to do with heat" How so, Sbharris? You argue "But neither energy or temperature is heat." Who is arguing this? Certainly not me! Then:- 1/ what is energy? Is work energy? Do chemical bonds contain energy? Is there potential energy in an elevated mass? 2/Do joules measure energy 3/Does a lump of iron at 10K; 100K; 1000K contain heat? Does it contain energy? If so, how can you calculate the energy at 10K; 100K; 1000K? If you... ...calculate the heat at 10K; 100K; 1000K? I would like to discuss the article but as the above shows, your response, addressed to me, has nothing to do with my arguments. --Damorbel (talk) 07:08, 23 November 2012 (UTC) Yes. But think of the possibility of some happiness for Damorbel if it is in the article!! And we are admitting that heat has a microscopic explanation and saying something about that in the article.Chjoaygame (talk) 05:02, 22 November 2012 (UTC) Chjoaygame, for long enough you have denied the role of the energy of particles in the thermodynamics of heat; now with your inclusion the Boltzmann constant with its dimension joules per particle per K you may have changed your position. I have always argued for revising the article to include what you were determined to reject, that thermodynamics, and thereby Heat, is all about the energy of particles. Now, after what seems to be a small step for you; we can proceed to a giant step for the article; so to speak. --Damorbel (talk) 11:22, 22 November 2012 (UTC) Dear Damorbel, you endlessly muddle yourself, and try to drag us into your muddle. You write: "you may have changed your position." I have not changed my position. At 03:39, 24 March 2012, I originated the section of the article initially entitled Motion of microscopic particles explains heat. It has been there, ready for you to put in details to your heart's content. But instead of doing that good thing, you frittered away your energy in sabotaging the work of other editors on other parts of the article. You write: "you have denied the role of the energy of particles in the thermodynamics of heat". I have denied that thermodynamics is concerned with particles, in which I am correct. I have not denied that the statistical mechanical explanation of thermodynamics is concerned with particles. The problem for us here is that you have persistently ignored the distinction between thermodynamics and statistical mechanics, and have tried to put the statistical mechanical explanation as primary without recognizing that it is an explanation of something more general and primarily empirically based. You still give yourself away here, when you write that "Heat is all about the energy of particles", which is a denial of the primary status of thermodynamics here. Well, at least we seem to agree that it is a fair thing that I did actually put in information including the Boltzmann constant into the section that evolved from my original one, and is now, owing to Waleswatcher, renamed Heat#Microscopic origin of heat. Sad to say, the ever destructive Waleswatcher has removed the reference to Boltzmann's constant. Perhaps you might take that up with him. Indeed I have noticed that you are very skilled at undoing edits. You are free to undo Waleswatcher's unjustified removal of the comment about the Boltzmann constant, or to replace it as you think fit with your own preferred version; I would urge you to keep it to the right part of the article, whence it was removed.Chjoaygame (talk) 19:19, 22 November 2012 (UTC)Chjoaygame (talk) 00:45, 23 November 2012 (UTC) I did actually put in information including the Boltzmann constant into the section. Can you give me a diff. for this? I couldn't find it. --Damorbel (talk) 09:40, 23 November 2012 (UTC) I put it in twice for you. First time that was subsequently removed by Waleswatcher. Second time that was subsequently removed by Waleswatcher.Chjoaygame (talk) 12:04, 23 November 2012 (UTC) Thanks! --Damorbel (talk) 12:15, 23 November 2012 (UTC) I removed it not because I think it's a bad idea to mention it, although it's not particularly central here, but just because it complicated that passage and wasn't needed to make the relevant point there. Where do you think it should go, Damorbel? Waleswatcher (talk) 14:13, 23 November 2012 (UTC) Rewording I did some rewording of the first parragraphs. Please review. Cheers! --Crio de la Paz (talk) 01:14, 22 November 2012 (UTC) Very well done!Chjoaygame (talk) 04:59, 22 November 2012 (UTC) Waleswatcher's current backward step Waleswatcher, you have practically reverted the most recent improvements in the article. Your reversions mostly just restore word for word your previous edits. It seems you feel a need to dictate the article, word for word, even when faults are pointed out in your dictated version.Chjoaygame (talk) 19:58, 22 November 2012 (UTC) I can't recall a time when you pointed out a single fault in any of my edits. Not that there aren't any - there are many - but you seem to be incapable of constructive or even specific discussion. Instead, you go off on vague rants such as this one, accusing me (and others) of all sorts of evils. Worse, your writing (in this and other articles) is stilted to the point of incomprehensibility. Physics is difficult and abstract, and it needs to be explained simply and clearly, using language most people can understand. It's hard to do this kind of writing well. Please try to contribute constructively. Waleswatcher (talk) 03:47, 23 November 2012 (UTC) Waleswatcher, where on the talk page? Waleswatcher made an edit at 05:23, 23 November 2012 with the cover note (rv as per talk page), but I don't find a corresponding entry on the talk page. The next edit by Waleswatcher, at 05:25, 23 November 2012 has the cover note (restored Chjoaygame's last edit which was unintentionally reverted), but that edit was not fully restored; only part of it was restored. Please, Waleswatcher, where is the talk page entry to which you refer?Chjoaygame (talk) 05:45, 23 November 2012 (UTC) It's all over the place. No one has given any physical reason or reliable source for separating convection from radiation and conduction. On the other side, both physics and a large number of sources list convection as one of the primary mechanisms for heat transfer. Waleswatcher (talk) 14:11, 23 November 2012 (UTC) In other words, you can't point to where it is. You are just bluffing us; or perhaps you are just bluffing yourself? In reality, there are three editors here who reject your bizarre story that there is very little physical distinction between radiative heat transfer and convective heat transfer. If you really believe that, let's see you source it and put it in the article!!! You respond to SBHarris thus: "Purely advected heat is not actually heat. I have no idea what you mean by that." Indeed it does seem that you have very little idea. I have given clear physical reasons: "The energy that is carried by convection is carried partly and importantly through the cooperation of the particles including their mutual potential energy, whereas for the most part, energy carried by a photon is the sole property of the photon. Also, convection is mainly one-way. One can have convection that is entirely one way. But radiative transfer is essentially two-way. This is because of the Helmholtz reciprocity principle. The heat transfer is the difference between the two ways. Photons carry energy from a source body constituent directly to a target body constituent, in one step. Convection essentially involves many particles on the way." Your response to this was evasive in the area of physics, and then wandered off into your views on pedagogy in the Wikipedia. Crio de la paz recognizes a difference between the physical and engineering accounts: "There _is_ an specific notion of _heat_ in _physics_thermodynamics_ that is fundamental to all of physics and it's applications. In engineering one deals with "heat transfer" phenomena ...", but he does seem to give you some vague support, which I think is indecisive. Reif, one of your two defining sources, does not mention convection, but talks at great length about conduction and radiation. The other of your defining sources, Kittel & Kroemer, mentions convection but not convection of heat, and that only once, in a problem. For the rest, it talks about conduction and radiation. That separates them. The difference is so obvious that no one would bother to make it explicit. It is amazing that you seem unable to see the difference, considering how obvious it is. If they really were the same, why would they be listed as three, instead of people routinely pointing out that they are the same? The idea that convection is of the same character as conduction and radiation is bizarre, an unsourced invention by you to justify your position. I do not deny that many sources list all three; I started by saying that I had been taught it when I was a schoolboy. That is not the point. The point is that the strict physical definition, upon which people here have been so dogmatic and insistent, refers only to conduction and radiation. SBHarris has pointed out that three steps are needed for convection: (1) conduction or radiation from the source heat bath into the carrier fluid, or work done on the carrier fluid, which add to its internal energy; (2) bulk flow of the carrier fluid with its contained internal energy; (3) conduction or radiation into the destination heat bath, or work done by the carrier fluid, by which it unloads the internal energy that it has carried. This is more complex than simple conduction or radiation, which you are trying to deny. And you have made no answer to my pointing out that when you said you had reverted, you had done so only partially, so that your statement was misleading.Chjoaygame (talk) 15:03, 23 November 2012 (UTC) Just FYI, I only read the beginning and end of your ridiculously long comments. Convection is discussed at length on this page; I have no idea what you expect me to point out to you other than that. Waleswatcher (talk) 20:50, 23 November 2012 (UTC) It is not news to me that you ignore what I write. You can ridicule it, and repeatedly say that you "have no idea"; no problem there. But you can't get the physics right; that's a problem.Chjoaygame (talk) 21:44, 23 November 2012 (UTC) It is energy that moves with temperature difference, It is energy that moves with temperature difference, 'heat' is not a Conserved quantity.--Damorbel (talk) 14:16, 23 November 2012 (UTC) Indeed, heat is not a conserved quantity. That's true by definition - heat exists only during transient processes, so it obviously cannot be conserved. Your point? Waleswatcher (talk) 14:25, 23 November 2012 (UTC) "heat exists only during transient processes" What is it that 'flows' then, in "Heat flow from high to low temperature"? (Heat article, 1st line, 2nd para? --Damorbel (talk) 16:16, 23 November 2012 (UTC) Energy. How many times have you asked that same question? And why is the answer so hard for you to grasp? Yes, the semantics are a little confusing, because heat is used differently in common parlance than in physics. And yes, "heat flow" and "heat transfer" are a bit redundant, since "heat" already implies a flow. But after months and months of being told the same thing, I would have thought you'd understand it by now. Waleswatcher (talk) 20:48, 23 November 2012 (UTC) Waleswatcher:Your [my] point? You say "heat exists only during transient processes" and the article says "Heat flow from high to low temperature occurs spontaneously" Now my point is that it is energy that goes from a high temperature to a low - as in a "heat" engine and it is energy that comes out - in the form of work along the crank shaft. The energy going in equals the energy coming out - conservation of energy OK? So my question is, in your (heat ) book, what is this transient heat that flows from hot to cold? Does it only exist when going in? In that case, what do you call the energy that comes out along the crank shaft, and what do you call the energy that comes out with the cooling water? --Damorbel (talk) 21:04, 23 November 2012 (UTC) Now my point is that it is energy that goes from a high temperature to a low...and it is energy that comes out - in the form of work along the crank shaft. And it is money that goes into your bank account, and money that comes out. But we still have terms for "salary" and "bill payment". As I said, I haven't a clue why you find this so hard to understand, so I'm afraid I give up trying to explain it to you. Waleswatcher (talk) 21:18, 23 November 2012 (UTC) "And it is money....." and "....I give up trying to explain..." I responded to this here: http://en.wikipedia.org/w/index.php?title=User_talk:Waleswatcher&oldid=524554339#Your_talk_page but it has since been removed. --Damorbel (talk) 07:48, 24 November 2012 (UTC) Heat Transfer One of the main problems with this discussion, that seems to be going in circles, is that we are mixing two different things. One is "heat", a concept in "thermodynamics" and another is the dynamics of "heat transfer". This is similar to confussing "work" as a concept of thermdynamics with dynamics (mechanics). When one annalyses a thermodynamic "system", it's changes between _equilibrium_ states and the ammount of heat and work that might exist through different paths one does not delve in, either, a mechanistic annalysis of how work is perfomed, nor of how heat is transfered nor of the internal dynamics of the system. Of course statistical mechanics does a lot into explaining phenomena that mechanistically explain some concepts as temperature, entropy, internal energy. Of course mechanics explains how forces do work. Of course heat transfer explains how heat is transfered from one place to another. But these are not _required_ from a classical thermodynamics stand point: wether heat is transfered via conduction, convection or radiation is not that relevant, in the thermodynamic annalysis of the system. If one, i.e., defines the system as a volume of control, all energy that crosses the borders of the volume of control _is_ heat: whether it includes mass transfer of not. That means that an influx of mass _implies_ an influx of energy: it implies "heat". If one does a balance of mass all the mass that enters the system minus all the mass that exits the system is accumulated in the system (in the volume of control). If one does a balance of energy one has that all the energy that enters the system minus all the energy that exits the system is accumulated in the system. (in the volume of control). Energy accumulation would be the enthalpy of incomming mass flux, minus the enthalpy of the exiting mass flux, plus the work done on the system, plus the heat absorbed by the system minus the heat released by the system. In this case it is clear that these last two "heaat" quantities imply _conduction_ and _radiation_, since _convective_ components are already considered with the enthalpy of the mass flux. Regarding entropy: the entropy accumulation within the system is the ammount of entropy carried by the flux of mass, pluss the entropy that is transfered between the sorroundings and the system generated by heat transfer, plus the entropy production within the system. If a system is closed this is simplified. Darmobel is finding it difficulty to understand the basic concepts of thermodynamics. Energy is exchanged between a system and it's sorroundigs through two different path dependent functions: heat and work. When heat is exchanged or work is performed it is _energy_ that is being transfer from one system to another. The work done by a force through a distance _is_energy_, the heat transfered from a body to another body _is_energy_. Energy conservation implies that, when two systems exchange energy through work or heat, energy is conserved. _But_ the ammount of energy that is actually avaiable to do work _diminishes_ with each process: in every process there is an ammount of energy that is realeased without performing work. Free energy is actually the energy avaiable for _doing_ work (either A=U-TS or G=H-TS). In a more general case where concentration of materials are studied and required (i.e. difussion) the uidNi must be taken into account (ui being the chemical potential of component i and dNi it's number of molecules or mols). At constant temperature and pressure dGtp=SUM(uiDNi). Advection misdirection I also responded to SBHarris: Actually when there is passive difussion there is an increase in entropy, see: http://www.rsc.org/learn-chemistry/content/filerepository/CMP/00/001/061/Why%20passive%20transport%20happens%20entropy.pdf?v=1352425760476 For a TS diagram of a heat pump figure 2 in http://en.wikipedia.org/wiki/Heat_pump_and_refrigeration_cycle is quite a good example. For a TS diagram of Carnot cycle see:http://en.wikipedia.org/wiki/Carnot_cycle Figure 2. Specially http://en.wikipedia.org/wiki/File:Carnot_Cycle2.png is of interest. The Carnot cycle is _the_most_eficient_ thermodynamic process between to different temperatures, where work is done isentropically and heat is released isothermally. Actually the example of you moving a cylinder of has is flawed: it is _quite_ inefficient ;-) and it is not reversible (you need to expend a lot of work in doing so: it is not reversible, it does not happen spontaneously). Advection and convection are not reversible, quite the contrary: they tend to be quite irreversible process: when a mass of fluid is heated up by a hot surface it rises. But it will not lower itself heating the surface back without external work. I forced convection one is _introducing_ an external force into the system in order to perform work in order to do process that _are_ irreversible. A reversible process is that which occurs spontaneously. You have taken much trouble to explain things here that I already understand. But let me return the favor by correcting your misconception about advection. You CAN do work advecting a hot object, but you need not, in theory. When I toss a hot thermos of coffee from one side of the ISS space station to the other side, Newton's first law is a big help. The only work is adding a wee bit of kinetic energy to the thermos, and it's entirely reversible (as can be seen if it hits something elastic and comes right back, at the same speed). Ideally, advection itself takes vanishingly small energy, and what it does take is reversible and does not of course increase entropy. Hence, advection is not heat transfer, but only energy transfer. Advection can transfer HUGE amounts of energy without ever transferring heat. SBHarris 22:19, 25 November 2012 (UTC) But I was not logged in: sorry! The main thing there being that in a thermodynamic cycle Carnot's cycle is the optimum cycle between 2 temperatures. At: http://en.wikipedia.org/wiki/Carnot_cycle One can check a TS and VP diagram for Carnot's cycle and see the ammount of heat exchanged at both isothermic ends and the ammount of work actually done. Sorry that I have not had the time to summarize my contributions here but I should be working! Wow: I am really amazed at how much of my physics, physical chemsitry, thermodynamics, transport phenomena and heat and mass transfer classes I do remember with a litte of work... I haven't really thought about these subjects in about 15 years!!! --Crio de la Paz (talk) 21:34, 23 November 2012 (UTC) Crio de la paz, please excuse me for reducing the space between your thoughts, it makes them a lot easier to follow. What you write suggests you are not following the discussion very well. There are two arguments here, one maintains that heat is some mysterious substance that appears when temperature differences exist. The other is that heat is the vibrational/kinetic energy of particles due to their temperature when above zero K. There that should help a little! --Damorbel (talk) 21:52, 23 November 2012 (UTC) As for your just above response to SBHarris. I hope I did the right thing. I didn't know if it was written by you or by someone else. In any case, I think I moved it to its natural home, to here? I hope so.Chjoaygame (talk) 22:02, 23 November 2012 (UTC) In physics, the difference between modes of internal energy transfer doesn't matter too much for some parts of classical thermodynamics, that is to say, for some parts of equilibrium thermodynamics. But for non-equilibrium thermodynamics, the distinction between conduction, radiation, and convection does matter.Chjoaygame (talk) 22:14, 23 November 2012 (UTC) The difference between transfers of internal energy as heat and work is not uniquely defined for open systems; so it is an arbitrary wording to say that the transfer with matter is heat; more systematic just to say that it is transfer of internal energy; some writers invent their own arbitrary distinctions and say they are specifically talking about "heat".Chjoaygame (talk) 22:14, 23 November 2012 (UTC) No, Darmobel, you are not quite understanding the basic aspects of thermodynamics: I told you the same thing that is in any thermodynamics book but you do not seem to grasp it. ΔU(T)=Q+W. What you are dubbing "heat" is "internal energy", not "heat". For any process in the universe where there is a change in energy in a system, the same ammount of energy is transfered to the sourroundings of the system by _two_mechanisms_: "heat" and "work". Total energy is _always_ conserved for an isolated system. If you divide an isolated system (i.e. "the universe") in two systems, the system you are annalyzing, and the "sorroundings" the ammount of change in the energy of the system is equal but of opposing sign the ammount of chage of the energy of the sorroundings. In _any_ physical process there is an exchange of heat, and in some work is done either on the system or by the system. The total ammount of change of energy in the universe must always be zero. But part of that energy is not avaiable to do work. The ammount of entropy by the temperature (TdS) gives the minimal ammount of energy "dispersed" as heat when transforming energy. "Heat" in physics is the ammount of energy transfered that did not do "work" in a given process. Darmobel: you are confusing the concepts of classical thermodynamics of "heat" and "thermal energy" or "internal "energy" or "enthalpy" depending on the situation. Of course that when "heat" is transfered from the system onto the sorroundings there is always a "mechanism", either conduction (which in statistical mechanics would be mostly energy of the particles that compose the system), or radiation (where electomagnetic waves/photons are exchanged until temperature is equilibrated) or, depending of your stand point even by convection (the concerted movement of a mass or a group of particles if you will within a fluid) or, maybe, gravitational waves (see http://www.omirp.it/www/Gravity+Gravitational_Waves/GW+Matter/GW_and_Matter.pdf). When work is transfered there is also a mechanism (a force that moves a body in a field or that changes it's inertial propierties. The field could be electrical, magnetic or modeled as an electromagnetic phenomena in relativity, could be gravitational or related to the weak or strong nuclear force. The inertial propierties might be equivalent or not to gravitational phenomena...). But in order to do thermodynamical analyisis one does not _need_ to delve into the intrincancies of the mechanics of such matters. Of course that when work is done and whe heat is transfered it is _energy_ that is being exchanged, not "a mysterious substance that appears when there is a temperature difference": but energy can be transfered in _two_forms_ (heat or work) from a system to it's sorroundings. Even more, for every physical process there is a minimal ammount of heat "realeased" that will not be avaiable to do work, save in ideal, reversible processess (TdS=Qrev) for the system and (TdS=Qrev) for the sorroundings, so the entropy of the "universe" (isolated system) remains the same on these procecess, but if you want to do work through a reversible process dE=W+Qrev => dE=W+TdS. That means that the energy avaiable to do work would be dE-TdS It is true what Chjoaygame says, in respect to, that, when there is a mass transfer it is a measure of it's internal energy (usually enthalpy that includes the presure volume component of the enery being transfered into the volume of control, if I remember correctly). I think Darmobel is missing a huge point in classical thermodynamics and it's fundamental laws of the conservation of energy, the necessity of some heat released when doing work, and the specification of the minimal ammout of heat required to do a process between two states. These laws are compatible with and even explained mechanistically by statistical mechanics, that is _true_ there he has a point. But the same is true for Von Newmann's generalization of entropy with regard to quantum mechanics, Shannon's entropy in information theory, black hole thermodynamics, etc. There are many mechanisms (of which statistical thermodynamics is a really important one) that are mechanistical models that are compatible with classical thermodynamics, but the general formulations of classical thermodynamics do not delve into them (wether it is "caloric" moving from one place to the other, electromagnetic waves, gravitational waves, energy residing in the vibration of molecules, it does not matter), it just starts from the concept that energy is conserved but that when there is a physical process some energy is transfered but does not do work, _ALWAYS_ for every single physical process, no matter what. Actually the measurement of the entropy of a black hole comes from this annalysis: "The only way to satisfy the second law of thermodynamics is to admit that black holes have entropy. If black holes carried no entropy, it would be possible to violate the second law by throwing mass into the black hole. The increase of the entropy of the black hole more than compensates for the decrease of the entropy carried by the object that was swallowed." http://en.wikipedia.org/wiki/Black_hole_thermodynamics. As the quote by the famous scientist Sir Arthur Stanley Eddington states: "The law that entropy always increases holds, I think, the supreme position among the laws of Nature. If someone points out to you that your pet theory of the universe is in disagreement with Maxwell's equations — then so much the worse for Maxwell's equations. If it is found to be contradicted by observation — well, these experimentalists do bungle things sometimes. But if your theory is found to be against the second law of thermodynamics I can give you no hope; there is nothing for it but to collapse in deepest humiliation." So I would avoid trying to find thought experiments or comparissions with courrency where people try to describes process where the entropy of the universe is not increased or, at most, remains the same, and where, when using energy to do "work", some of the energy, at least δQrev=TdS, is not usefull for work. --Crio de la Paz (talk) 23:44, 23 November 2012 (UTC) Or: The second law of thermodynamics is, without a doubt, one of the most perfect laws in physics. Any reproducible violation of it, however small, would bring the discoverer great riches as well as a trip to Stockholm. The world’s energy problems would be solved at one stroke. It is not possible to find any other law (except, perhaps, for super selection rules such as charge conservation) for which a proposed violation would bring more skepticism than this one. Not even Maxwell’s laws of electricity or Newton’s law of gravitation are so sacrosanct, for each has measurable corrections coming from quantum effects or general relativity. The law has caught the attention of poets and philosophers and has been called the greatest scientific achievement of the nineteenth century. Engels disliked it, for it supported opposition to Dialectical Materialism, while Pope Pius XII regarded it as proving the existence of a higher being. Ivan P. Bazarov, "Thermodynamics" (1964)--Crio de la Paz (talk) 23:56, 23 November 2012 (UTC) A theory is the more impressive the greater the simplicity of its premises, the more different kinds of things it relates, and the more extended its area of applicability. Therefore the deep impression that classical thermodynamics made upon me. It is the only physical theory of universal content which I am convinced will never be overthrown, within the framework of applicability of its basic concepts. Albert Einstein (author), Paul Arthur, Schilpp (editor). Autobiographical Notes. A Centennial Edition. Open Court Publishing Company. 1979. p. 31 [As quoted by Don Howard, John Stachel. Einstein: The Formative Years, 1879-1909 (Einstein Studies, vol. 8). Birkhäuser Boston. 2000. p. 1] Can somebody please clean this mess up? It is completely impenetrable, close to disruptive editing. For example: No, Darmobel, you are not quite understanding the basic aspects of thermodynamics: I told you the same thing that is in any thermodynamics book but you do not seem to grasp it. ΔU(T)=Q+W. What you are dubbing "heat" is "internal energy", not "heat" How can I possibly respond to an item that, without a reference, begins No, Darmobel....? --Damorbel (talk) 08:05, 24 November 2012 (UTC) Conservation of ' 'Heat ' ' ? Heat is not a conserved quantity so, in thermodynamic terms, it cannot be transferred. What is transferred is energy. The article should make clear that common usage does not explain subtle differences in language. The Heat article currently doesn't explain these subtle differences either; this is a serious deficiency because it contains statements such as :- Heat flow from high to low temperature occurs spontaneously (Opening statement, 2ndpara 1stline) which is thermodynamic nonsense because it does not respect the conservation of energy according to the 1st Law of thermodynamics. --Damorbel (talk) 08:47, 24 November 2012 (UTC) Nope: 'work' and 'heat' are forms of _transfer_ of energy. Neither is conserved. What is conserved is _energy_ not 'work' and not 'heat'. Nobody is saying (only Darmobel) that "heat is conserved". Energy is conserved and for any thermodynamic process 'heat' must be released when doing 'work'. ΔE=Q+W. What flows spontaneously from high to low temperature is 'heat' which is _a_form_ of energy transfer. In that (when only heat is tranfered) case W=0 and ΔE=Q: the change in energy is exactly the ammount of heat released. But when work is also being done then ΔE=Q+W. Energy is used to do work _but_ some energy is transfered as heat _always_. What this means is that not all energy is avaiable to do work. The minimal ammount of heat released during a process is δQrev=TdS: in general ΔS>=Q/T. Notice that is not "ΔQ": there is not a "heat change" there is an "energy change" where energy is tranfered via 'heat' with no 'work'. There are two main phenomena for energy transfer: 'heat' and 'work', which are distinct and are not conserved in themselves: that which is conserved is energy (for an isolated system) ΔETOT=0. This is why the first law of thermodynamics is stated as ΔE=Q+W or as ΔU(T)=Q+W when only the internal energy of the system is used. This internal energy might have been at a time considered only as 'thermal energy' but nowdays we know there is also "chemical energy" and "nuclear energy", etc., involved. Darmobel is missing the basic point of the laws of thermodynamics entirely, especialy the second law. He wants "heat" to be "thermal energy", which it is not. The main point of the laws of thermodynamics is that, when you use energy to do work some of the energy is _always_ transfered but not used as work. These concepts arose from a generalization of real world observations of physical processes: it is by no means self evident, but it seems to be the truth in the universe we live in, similarly to the arrow of time or that the velocity of light in a vacuum is a constant. The laws of thermodynamics (as happened with Newton's laws of motion) _might_ be disproven for some generalized case, but that has not been the case (as per the quotes if somebody finds a case where the laws of thermodynamics do not hold he or she probably would win a Nobel Prize of physics and hailed as greater than Einstein, Newton Et.al. all together. Even when studying black holes the concepts of conservation and of the increase in entropy of the universe and conservation of information arise). What Darmobel is missing is not easy matter to understand: the need for 'heat' that arises when realising that, when using 'energy' for doing 'work', not all 'energy' that is transfered is used as 'work' but some is transfered and not transformed into 'work'. This is the quantity that in thermodynamics is called 'heat'. This means that perpetuum mobile of the second kind _does_not_exist_ Whenever you use 'energy' to do 'work' some 'energy' is transfered but not used to do 'work'. These concepts began as an analysis of thermal engines and thermal procecess but later ere generalized as laws for "the universe". The interesting thing is that these "laws" have never being disproved but actually seem to hold in one form or another for all physical processes. It seemed to be a bold move to generalize the laws of thermodynamics to _every_physical_process_in_the_universe_ but, up until this day and age, there is not a single process where the laws of thermodynamics are not obeyed. Darmobel: the concept of 'heat' in physics arises when it is realized that an energy change cannot be used only to generate work. The rest of the energy that is tranfered is then called 'heat' and it seems to be related to a gradient in the quantity called temperature. Even in the study of "heat transfer' the differences in temperature are an important part of the velocity at which heat transfer occurs. Depending of the mechanism the dependence is different. In conduction the quantity of heat flow is a function of the gradient of temperature (dQ=kAdT/dx in one dimmenssion), in convection it is a function of a generalized gradient of temperature(dQ=hAdT), in radiation a function of the fourth power of temperature (dQ=σεdAT^4). Actually here we have a distinction between convection and conduction, even more established by Nusselt's number Nu=(h/k)L, where L is a characteristic distance. Here we have a ratio of convective heat transfer over conductive heat transfer. In http://en.wikipedia.org/wiki/Nusselt_number One can find a derivation of Nusselt's number from Fourier's equation. When one delves into the details of dimenssional annalysis and convection one starts to realize that the mechanics of heat transfer through convenction are, indeed, distinct from conduction and radiation... --186.32.17.47 (talk) 15:47, 24 November 2012 (UTC) Nameless 186.32.17.47 - You write:- " Nobody is saying (only Darmobel) that "heat is conserved"" I doubt if I ever wrote Heat was conserved I opened this section and it has the title Conservation of ' 'Heat ' ' ?, the question mark is important. If you did not realise that I have been arguing the importance of the consevation of energy, not heat, for some time, then you may be struggling with the whole matter. Nameless 186.32.17.47, you write What flows spontaneously from high to low temperature is 'heat' which is _a_form_ of energy transfer. Well written" Why don't you open a section enttled Conservation of ' 'Heat ' ' ? Nameless 186.32.17.47, you write Darmobel: the concept of 'heat' in physics arises when it is realized that an energy change cannot be used only to generate.... Which of course raises the question: do you have special evening for teaching your grandmother to suck eggs? --Damorbel (talk) 22:00, 24 November 2012 (UTC) In the immediately foregoing, written I guess by Crio de la paz, good points are made, I think.Chjoaygame (talk) 17:46, 24 November 2012 (UTC) I agree - heat and work are process functions, not state functions. They are not something associated with a state. Asking how much heat a system contains is like asking how much work it contains. It's nonsense. You must ask how much work has a system done, how much heating has it done, etc. A system may lose internal energy by doing work or by heating another system, or may gain internal energy by having work done on it or by cooling another system. This idea is at odds with the non-scientific use of the word heat, the idea that a hot body contains a lot of heat, a cool body not so much. If we are going to speak scientifically, then we must use the scientific definition of heat and not confuse it with the unscientific common-usage "definition". PAR (talk) 18:13, 24 November 2012 (UTC) PAR, you write:- "heat and work are process functions, not state functions." Do you recognise any connection between heat and temperature? Or between temperature and energy? Or between temperature and state functions? --Damorbel (talk) 22:00, 24 November 2012 (UTC) I do not understand what the whole "teaching your grandmother to suck eggs" reference is about. PAR and Chjoaygame are right but Darmobel seems only to be trying to pick a fight. If he already undertsand these subjects then: What is he arguing about? Where has _anybody_ argued that "heat is conserved" or that "some mysterious substance that appears when temperature differences exist" besides him? If he already understands all we are saying and he does not require any explanation on thermodynamics: What is he arguing about? For all I've read in these discussions he is arguing only with himself. --Crio (talk) 00:44, 25 November 2012 (UTC) This is a confusion of the everyday usage of the word heat and the thermodynamic definition. In the thermodynamic definition, heat and work are mathematically similar. The problem is in the English. If "work" and "heat" were to be made as similar verbally as they are mathematically, we could write: A system transfers energy to another system by doing work on it. A system transfers energy to another system by doing heat on it. A system transfers energy to another system by working it. A system transfers energy to another system by heating it. Work is something that is done, it does not "exist". Heat is something that is done, it does not "exist". PdV represents the amount of energy transferred by work. TdS represents the amount of energy transferred by heat. Some of these sentences sound odd - they conflict with everyday English usage. Damorbel has failed to realize that the problem with these sentences is not with the physics, it is with the English. The word "heat" was perhaps a bad choice for TdS, but we seem to be stuck with it, and we have to deal with it and not declare that the English language guides the physics. You don't "do heat" the way you "do work", but rather, you "heat". You don't say "heat is done, it does not exist", you say "heating is done, it does not exist". You don't say "TdS is the energy transferred by heat", you say "TdS is the energy transferred by heating". That's an unfortunate verbal mess, but it has nothing to do with the physics. As regards "thermal energy", I don't know the rigorous definition. If I have a box with a piece of ice in it at the temperature of the triple point, and I then heat the system until all the ice turns to water, it is still at the triple point temperature. The temperature has not changed, but the internal energy has increased because entropy has increased. Has the "thermal energy" increased? I don't know. PAR (talk) 16:20, 25 November 2012 (UTC) PAR referring to your , it is still at the triple point temperature...". In practical terms this wouldn't happen because the water would not turn to ice at the same instant. The triple point cell does not normally allow much heating or cooling, it is supposed to be an equilibrium cell, where energy exchanges occur only between the ice, the water and the vapour, the total cell energy should remain constant. I am interested in this post, I hope to return later, you identify misunderstanding via language as a problem - I agree with you!--Damorbel (talk) 16:54, 25 November 2012 (UTC) This is not correct. You can heat a fixed-volume system containing ice, water, and vapor at the triple point. Let it equilibrate. As long as you have not added enough energy to melt all of the ice, the temperature will still be at the triple point. There will just be more water and less ice. That's why a triple point cell is so useful - heat it, cool it, work it, make it work, thereby adding or subtracting from its internal energy. When it comes to equilibrium, it will still be at the triple point as long as the three phases still coexist. The internal energy will have changed because the entropy has changed, but the temperature will not have changed. PAR (talk) 19:10, 25 November 2012 (UTC) What you said is "....until all the ice turns to water That means that the buffering effect of the ice is no longer working..... But I understand what you mean! A system transfers energy to another system by doing work on it. The effect you get depends on how the work is done - if the system is a shell (in the barrel of a gun) work done is the propellant pushing the shell out of the barrel and the work gives the shell velocity. If you are forging a billet of steel the work is changing the shape of the billet and it gets hotter A system transfers energy to another system by doing heat on it. The gun's propellant burns in the breech, producing hot gas that heats the barrel. A system transfers energy to another system by working it. 1/When forging a billet of steel the work is changing the shape of the billet and it gets hotter 2/When bending a nail stuck in a plank of wood the nail gets hot fron the internal friction resisting the force bending the nail, A system transfers energy to another system by heating it. The gun's propellant burns in the breech, producing hot gas that heats the barrel. Work is something that is done, it does not "exist". The work done by the propellant gas accelerates the (depleted uranium anti-tank) shell to 1500m/s, giving it a lot of kinetic energy. The (depleted uranium anti-tank) shell hits the enemy tank, deforming the tank and, by means of friction, the tank brings the shell's 1500m/s velocity to zero. This friction changes the kinetic energy of the shell into heat, and induces chemical change by cooking the people in the tank. Heat is something that is done, it does not "exist". There is chemical (thus potential) energy in the propellant, waiting for someone to trigger its release. When burning, the propellant decomposes to gas which is very hot (flames and suchlike) and so at a high pressure, this hot gas forces the (depleted uranium anti-tank) shell out of the barrel. The potential energy in the propellant does a number of things 1/it raises the temperature and pressure of the combustion gases 2/ it heats the gun's barrel and 3/pushes the shell out of the gun at high speed; cooking the enemy in their tank. From this you will realise that the chemical energy, when triggered, is spread all over the place but it is not destroyed it just gets spread around to lower and lower concentrations, always lower than the orignal (chemical) energy in the propellant. PdV represents the amount of energy transferred by work. Only if it is a gas that is worked on and only if the action is adiabatic. TdS represents the amount of energy transferred by heat. Depends on what dS means. Is the system at maximum entropy. I assume there is only one source of energy, but it the energy doesn't have to be evenly distributed, perhaps there is (= there always is) a gravitational field.--Damorbel (talk) 21:49, 25 November 2012 (UTC) I wrote above:- the chemical energy, when triggered, is spread all over the place but it is not destroyed it just gets spread around to lower and lower concentrations, always lower than the orignal (chemical) energy in the propellant. What I should have mentioned is that the total energy released by burning the propellant remains traceable i.e. it is conserved but it is continually changing its form: from chemical energy to heat: to kinetic energy of the gas and the shell: to low temperature energ in the gun barrel: back to heat energy, possibly hotter than the combustion products when the shell strikes the tank. Other energy products from triggering the propellant are sound and perhaps gravitational potential energy - I invite contributions! But also it should be noted that none of the combustion energy is transformed into another conserved quantity such as momentum. --Damorbel (talk) 07:04, 26 November 2012 (UTC) The simple answer to your question is that "thermal energy" is undefined and is a bad term to use because it seems to have meaning when it does not. Likewise thermal internal energy which suggests we can identify what part of U came from heat and what didn't. If you have a sample of hot gas, did it get hot from compression PdV or heating TdS? No way to know. Either is possible or some combo. To pretend you know, perhaps by crystal ball, is fooling yourself and others. Thus there is no heat content. There is no latent heat content. Potential energy goes up in a phase change, and that's the way internal energy is stored, but you don't know how it got there or how that energy will come out, so you're kidding yourself if you think it's tagged by Mother Nature as "thermal" energy. It's just potential energy. It follows that heat cannot be advected. Heat is not, and cannot be, stored. Heat is not a noun! As declares a famous pedagogical paper. This all goes back to Mark Zemanski's opus of 1970, called "The Use and Misuse of the Word "Heat" In Physics". Still widely cited after 42 years (but still not online, alas). But also widely ignored by college text writing boobs, which makes well-nigh impossible to cover these topics on Wikipedia. Much as happened with "weight" and "matter". There are ten careless writers for every rigorous one. And WP editors would rather win an argument than think. SBHarris 17:15, 25 November 2012 (UTC) SBHarris writes words of wisdom: "There are ten careless writers for every rigorous one." His next sentence I think needs a slight amendment, the addition of the word some: "And some WP editors would rather win an argument than think."Chjoaygame (talk) 18:51, 25 November 2012 (UTC) definition of heat in this article The present article starts by defining heat in a way not precisely that of any particular reliable source. The sources cited are Reif and Kittel & Kroemer, two student texts of statistical or thermal physics. They both come from a particular pedagogical viewpoint, that one should teach thermodynamics along with statistical mechanics. In his introduction, Reif makes the point that he thinks he is particularly clever to do this. Another well represented pedagogical viewpoint is that thermodynamics should be taught separately from and prior to statistical mechanics. The reason for the latter viewpoint is that it is good for the physicist to have a good grasp of what can be done with thermodynamics alone, without calling on the special notions of statistical mechanics. The present article's precise wording is nearer to Reif's than to Kittel & Kroemer's definition. The article's definition omits the word "purely" from Reif's definition. Reif, like most sources, defines heat in a carefully constructed context, and does not intend his definition to make sense without that context. The present article's definition omits that context. It follows that the present article's definition of heat is original research. Reif defines heat in a context of classical thermodynamics. There are two bodies which can interact by exchanging energy. There are, according to Reif here, two types of interaction available for them. Reif has already defined a system or body in specific terms; the terms point to the working body of a classical thermodynamic system, defined statically by external parameters. Regrettably, as a result of his pedagogical stance, Reif's definition is partly clouded by its inclusion of loosely worded ideas that refer vaguely to the quantum mechanical Hamiltonian, with the result that the context of his sentence that introduces the word heat on page 67 is complicated or even, one might say, cluttered. Kittel & Kroemer are likewise practitioners of the mixed-teaching pedagogical persuasion. They do not use the same definition as Reif, though the difference does not amount to a significant conflict. They specify on page 227 that "Heat is the transfer of energy to a system by thermal contact with a reservoir." Their reservoir is assumed to possess a well-defined temperature. The term "thermal contact" is worth examining. It comes from a tradition of rigorous classical thermodynamic thinking started by Bryan, and continued by Carathéodory, and blessed by the authority of Born. The tradition examines very simple assemblies of bodies of respectively homogeneous chemical constitution, in communication with each other through defined partitions. The partitions are considered to be permeable to or capable of transferring energy or matter in specific ways. Amongst the ways is the thermal way, in Carathéodory's translated words, "as heat". This refers to the case when matter cannot permeate the partition, and where the partition does not move so as to produce volume-related work, and where external long-range forces are invariant. Carathéodory is burning to obey Born's advice to follow up on Bryan's observation that if one relies on the principle of conservation of energy as a prior supposition, or if one imagines that one can perform reversible work, then one can simply define heat transfer as transfer of energy that is not as work. This thinking is often regarded with awe as brilliant physical insight. Carathéodory admits the existence of partitions permeable only to "heat", but he carefully words his definition of them so that the words heat and temperature are not explicit in them. Indeed, he continues his article without actually offering a definition of heat according to his scheme of development of the basic ideas of classical thermodynamics for closed systems. Nevertheless, his scheme has built into it, for its definition of the equilibrium states of parts of his systems (the only states defined in his development), a "non-deformation" variable, that other more traditional developments would regard as a potential measure of empirical temparature, Carathéodory's development carefully avoids explicit mention of empirical temperature. Thus for Carathéodory, the father of this very rigorous way of thinking, heat is transferred by conduction or by radiation, though, for the sake of the brillianct cleverness of the development, the wording is carefully constructed to hide this fact, a fact which appears clearly in other more traditional developments that do not consider themselves quite as brilliantly clever as Carathéodory. Many texts, such as Reif and Kittel & Kroemer, in developing the notion of transfer of energy as heat, do not proceed to discuss the first law of thermodynamics for open systems, but restrict their systematic development to closed systems.Chjoaygame (talk) 17:40, 24 November 2012 (UTC) Response by Crio Quite an interesting exposition Chjoaygame! --Crio (talk) 00:50, 25 November 2012 (UTC) Response by Damorbel Looking at your sources (BTW, please don't cite sources without refencing some relevant passage(s)):- Kittel & Kroemer on the 1st law of themodynamics p49:- First law. Heat is a form of energy. This law is no more than a statement of the principle of the conservation of energy, Ch.8 discusses what form of energy heat is. Ch.8Has the heading :- Energy and entropy transfer Definition of Heat and Work They open:- Heat and work are two different forms of energy transfer but heat is not a conserved quantity. Later they go on about entropy transferbut entropy is not a conserved quantity. Thus form the beginning Kittel & Kroemer are mixing conserved and none conserved items and not drawing attention to the fact that only conserved items can be transferred, non-conserved items can appear or disappear, sometimes without trace, e.g. chemical energy and kinetic energy. Thus Kittel & Kroemer cannot be considered as a reliable source on the first law of thermodynamics, so the the rest of their arguments are necessarily quite doubtful.--Damorbel (talk) 10:43, 25 November 2012 (UTC) Dear Darmorbel, contrary to your comment, they are not my sources; they are, as I wrote, the sources cited in the article, which gives the relevant page numbers, only p. 227 in the case of K & K, not the p. 49 to which you further refer. I am not proposing that these sources are, or are not, reliable. I am pointing that they are the ones cited in the article for its definition, though that definition does not follow them precisely, and is therefore original research. By the way, you are utterly mistaken to say that only conserved quantities can be transferred. In systems which can gain or lose bulk potential energy by long-range forces with the surroundings, internal energy is not conserved, but can be transferred. It is customary in the field theory of non-equilibrium thermodynamics to say that entropy can be transferred, though at least one writer, B.C. Eu, uses a specially invented word, "calortropy", to deal with the concern that "entropy" can be created as well as transferred, which should make you happy. Above, you say that you are "arguing that Kinetic theory ... is ... at the base [italics by Chjoaygame] of thermodynamics and statistical mechanics". You are missing a main point there. No one is denying that kinetic theory or statistical mechanics can be considered to be "at the base [italics by Chjoaygame] of thermodynamics"; I think it clearer to say that they explain thermodynamics, though many people, including you, like to say that the explanation is "basic", relegating thermodynamics proper to a derivative or secondary status. What is being said, and is the consensus here, is that for the definition of quantity of energy transferred as heat, thermodynamics provides the primary definition, which is then exported to statistical thermodynamics, there to provide the target propositions that it aims to derive and thus explain in terms of the microscopic picture. How many times do we need to repeat this to you, before you hoist it in? One problem here is that much of the time you are arguing against straw men of your own making, misrepresenting what we try to tell you.Chjoaygame (talk) 11:47, 25 November 2012 (UTC) Chjoaygame, you write they are not my sources; Who cares whether they are your sources? The article is not "your article". Kittel & Kroemer are in the article, they are being used to support unsupportable 1st Law assertions (heat flow.) Further you write:- B.C. Eu, uses a specially invented word, "calortropy" Possibly related to caloric? Chjoaygame without explaning its relevance to the Heat article. This comment is utterly irrelevant and is time wasting. Usng this kind of logic you must not be surprised when your contributions get reversed. Please stop this kind of disruptive editing. As regards reliable references WRT kinetic theory and thermodynamics you will find that the Royal Society and Sir Humphry Davy denied that heat was a property of molecules and deliberately obstructed publications on the matter (see here) so the aricle in distinguished company with Kittel & Kroemer as references! Further you write:- By the way, you are utterly mistaken to say that only conserved quantities can be transferred. Really? You go on toexplain with:- In systems which can gain or lose bulk potential energy by long-range forces with the surroundings, internal energy is not conserved Who is saying internal energy should be conserved? Please explain, this idea cannot possibly be supported in Wikipedia. --Damorbel (talk) 13:06, 25 November 2012 (UTC) Damorbel, you write tetchily: "Chjoaygame, you write they are not my sources; Who cares whether they are your sources?" Damorbel, you care, as is shown by your gratuitously attributing them to me, a straw man of your own creation. In fact I had written: "... contrary to your comment, they are not my sources." Dear Damorbel, you now misrepresent my response to a previous misrepresentation by you of what I wrote previously. Previously you inaccurately wrote that they were my sources; I was just observing that I had written that they are the article's sources; I was just corrrecting your inaccurate statement about what I wrote. Now you try to make out that this means that I am engaging in disruptive editing. And next you write further erratic and irrational remarks. Your misrepresentations are too much. I don't have time for your antics. Why do we reply to you at all? We know from painful experience that trying to discuss physics with you is futile because of the way you behave. You have a current invitation by other editors, to put into the section on the statistical mechanical explanation what you want to about the Boltzmann constant, your heart's desire, but instead of doing so, you turn aside to behave so as to make another editor write just above here: "... Damorbel seems only to be trying to pick a fight." Chjoaygame (talk) 14:08, 25 November 2012 (UTC) Comment by Chjoaygame No one has responded to my statement at the beginning of this section, that the present article's definition of heat is original research. A reasonable response would be that the lead is a summary and cannot be required to be limited to exactly sourced material; it should accurately summarize the properly sourced material of the body of the article.Chjoaygame (talk) 22:04, 25 November 2012 (UTC) I don't have it here to check, but the definition in the first line of the article is nearly verbatim K&K's definition of heat, isn't it? If so, how in the world can you construe that as "original research"? Are you familiar with the meaning of the phrase? Waleswatcher (talk) No, it isn't "nearly verbatim K&K's definition of heat". When you wrote the above, you were not in a position to ask any rhetorical questions, let alone insulting ones. Please come back to us when you have done your homework.Chjoaygame (talk) 02:34, 26 November 2012 (UTC) "Homework" - you have a very bizarre idea of what this talk page is for, don't you? Anyway, I checked. According to K&K, "heat is the transfer of energy to a system by thermal contact with a reservoir". Doesn't quite coincide with our first sentence, but "original research"? As I suspected, you clearly have no idea what that phrase means. Now why don't you go do your "homework" and get us Reif's definition, Chjoaygame. Waleswatcher (talk) 04:15, 26 November 2012 (UTC) Good of you to do at least half of your homework; thank you. As I remarked above, Reif's definition includes essential context, which takes nearly a page, but is not supplied in the lead definition in the article. It cannot be copied safely here without copyright problems, I think.Chjoaygame (talk) 04:52, 26 November 2012 (UTC) Waleswatcher, there is no way Kittel & Kroemer can be considered a reliable source on thermal physics. They are both highly qualified and have published an interesting book but neither have a background in teching the matter, Kittel is a solid state physicist and Kroemer a solid state engineer. In no way does it rule out their book but it does mean that, when citing it, it is necessary to examine what they have written. I regard reliable sources papers by people like Fourier, Einstein and Clausius. Such people have defended their theories and we may attack them (if we dare!). The problem with Kittel & Kroemer is over the first law of thermodynamics; on p49 they have:- Heat is a form of energy [true, but then] This law is no more than the principle of conservation of energy. It isn't, it is the energy that is conserved, but it need not be as heat, it may well be (and frequently is) chemical energy. The arguments put forward by Kittel & Kroemer for their "Thermal Physics" fall down badly on the fundamentals, they treat thermal energy as a conserved quantity, it isn't. What is conserved is the energy of the heat but the whole of modern physics revolves around the fact that energy has many different forms, Heat, potential energy, chemical energy, sound energy, electrical energy etc.etc. None of these forms are conserved, that is why Heat flow (in the article) is not a scientific concept. I am not saying that Heat flow should not appear in the article, it should, but it must be put in the category of practical but unscientifc ideas about heat. --Damorbel (talk) 09:58, 26 November 2012 (UTC) The immediately above comment by Damorbel is mostly drivel. I would say that Waleswatcher has no need to respond to such drivel.Chjoaygame (talk) 11:01, 26 November 2012 (UTC) Good morning Chjoaygame. I would like to know why you think my contribution is drivel. Also I think you owe it to the other users of Wiipedia to show them you can manage better than simple abuse. --Damorbel (talk) 11:55, 26 November 2012 (UTC) Damorbel, K&K is plainly a reliable source for this article. If you don't believe me, please go and read wiki's guidelines for reliable sources. You might note that K&K is one of the standard texts for undergraduate and Ph.D. level courses in thermal physics and statistical mechanics. Regarding the physics in your comment, I've decided to stop engaging you (and to a lesser extent, everyone else here) on physics unless it is directly related to a specific edit of the page. Waleswatcher (talk) 13:26, 26 November 2012 (UTC) So if Kittel & Kroemer say that heat is a conserved quantity that is right is it? And if Richard Tolman - Principles of Statistical Mechanics. p 528 section 118. 1st para p529 section 119 says it isn't then he is somehow just - wrong? Waleswatcher, there are some things in life that you have to be able to work out for yourself; I invite you to read Kittel & Kroemer and Tolman and explain which is the better argument. --Damorbel (talk) 14:00, 26 November 2012 (UTC) Further comment This section is relevant because Waleswatcher wants to put convection in the lead on the same status as conduction and radiation as modes of transfer of energy as heat. The definition that he adverts to just above, "heat is the transfer of energy to a system by contact with a reservoir", is taken from the student text by K&K in which the exact word "convection" does not appear at all, and in which the nearest to it is the term "convective isentropic equilibrium of the atmosphere"; the rest of the book concentrates on conduction and radiation. The other cited source, Reif, mentions convection only in order to exclude it, while the rest of Reif's book concentrates on conduction and radiation. Waleswatcher here is minimizing the departure of the article definition from its cited sources, that is to say, minimizing its aspect of original research. Apparently this minimizing of the aspect of original research is in order to bolster his effort to put convection in the lead on same status as conduction and radiation. I would describe this as spinning by Waleswatcher.Chjoaygame (talk) 08:19, 26 November 2012 (UTC) As is his nature, Waleswatcher has now made a trivial edit that he thinks further minimizes the problem with the lead. He has replaced the word body with the word system, which is vague as to the important point that it is a closed system that is being considered. He is referring to the definition of Reif. He continues to omit the important word "purely" used by Reif; it is hard to be sure, but it seems perhaps that his cover note intends to excuse this omission by appeal to something about Wiki style? He writes an unusually long cover note because it is beneath his dignity to reply here on the talk page. But not long enough to actually deal clearly with the problem. And as for context in K & K, Waleswatcher omits their "contact with a reservoir", which for them has a temperature. Thus Waleswatcher continues to omit the important contexts indicated by K & K and by Reif. He also avoids mention of the important absence of convection from either K & K or Reif. He is a master of spin, but not of physics.Chjoaygame (talk) 16:35, 26 November 2012 (UTC)Chjoaygame (talk) 16:46, 26 November 2012 (UTC) Your problem, Chjoaygame, is that you are an atrocious writer. You are incapable of writing coherently even here on talk pages, let alone in articles. You persist in embellishing, qualifying, decorating, and otherwise festooning your prose with so many unnecessary and overly elaborate semantic details that even an expert in the topic can barely follow them, let alone some innocent layperson that simply wants to know what "heat" is. When I read articles you've edited, I can see right away what part you wrote and what anyone else wrote. If you get nothing else from this discussion, at least understand that you need to learn how to write. Learning how not to insult and antagonize anyone that disagrees with you or prunes your bloviations would help, too. The first sentence of the lead of a wiki article is supposed to succinctly introduce the subject. It should have the title of the article in bold, preferably as the first word or phrase of the sentence. It is not the place to insert caveats, details, or if at all possible terms with a meaning that won't be clear to the average reader. That's what the rest of the article is for, to explain the details. As for your patently absurd assertion that the first line is "original research", there's no point in even commenting on it further. From this point on, I will no longer respond to you on the talk page, as it is a clear waste of my time. The only exception will be if you have a specific objection or suggestion to a specific passage in the article. If you think "purely" is important, why haven't you edited it in rather than wasting everyone's time? Waleswatcher (talk) 21:10, 26 November 2012 (UTC) Comment by Count Iblis Thermodynamics is part of physics, and in physics we tend to put things in a broader context. Physics is, after all, about describing Nature and there are no imaginary boundaries between subjects such as electromagnetism, relativity, thermodynamics etc. etc. in Nature. When you do an experiment, you are dealing with all of Nature, not some aspect of it that only exists in some limit. This is why I support he way Reif treats this subjects. He approaches the topic from the point of view of physics, he motivates what he is doing, justifies approximations etc. etc. Count Iblis (talk) 23:30, 25 November 2012 (UTC) The reason that I said there is a departure from sources, that warrants the technical term own research, is that the definition in the article departs from that of Reif, its closest source, by omitting the careful setting of context that Reif offers, and by omitting the word "purely" that he puts in front of "thermal". I further pointed out that Reif's book does not have the word convection in its index; I may now add that a computer search through Amazon reveals just one use of the word in its text, as follows. On page 492, in problem 12.15, Reif considers an experiment. He writes: "In the absence of any convection in the gas, make a rough estimate ..." I also pointed out that Kittel & Kroemer do not write the exact word 'convection' at all; they pose one problem in which they write of "convective isentropic equilibrium of the atmosphere".Chjoaygame (talk) 02:28, 26 November 2012 (UTC) Reif does consider some specific examples, but the main definition is based on the definition of macroscopic work. The First Law is then taken to be the definition of heat, I think Reif makes that very clear. So, the question is then how Reif defines macroscopic work. This is done in terms of external parameters which define some macroscopic properties (constraints) of a system, such as the volume. A change in these external parameters will lead to a change in the internal energy. The work done by a system is the decrease in the internal energy due to the change in the external parameters. And here you always have to consider an ensemble of systems and take mean values to make this well defined. Count Iblis (talk) 03:42, 26 November 2012 (UTC) It seems you and I agree here, in the major point that Reif states his definition carefully, referring explicitly to a context of closed systems, allowed only to exchange heat, through a diathermic partition, when the adiabatic partition is removed. Reif also follows the Bryan-Carathéodory-Born tradition of considering heat as strictly defined as a residual from work transfer, with respect to a strict requirement for conservation of energy and a well-defined internal energy, work being defined, as you note, by changes in external parameters under an adiabatic constraint. Reif does indeed consider an ensemble of systems, because his context is that of quantum statistical mechanics. The present article takes instead the point of view of thermodynamics in its plain sense. I think you would like the article to change its point of view to that of quantum statistical mechanics.Chjoaygame (talk) 05:22, 26 November 2012 (UTC) Thermodynamic and mechanistic explanations Statements above like: " A proper explanation of heat has to be based on the energy contained in the motion of particles, not on the transfer of that energy between particles" by Damorbel ilustrate the problem with some of these approaches. Even though the laws of thermodynamics predate statistical mechanics and do not require it in order to be formulated (but are explained, in some cases, by it) when texts rely on statistical mechanics in order to explain thermodynamics they create confussion. The basic laws and concepts of thermodynamics were well under way before being "explained" by statistical mechanics and are compatible also with, i.e., Von Neuman entropy, Shannon entropy, Balck hole entropy, the entropy of gravitational fields, etc. That the mechanistic approach of statistical mechanics is compatible with classical thermodynamics is true, as are Newton's laws of motion, regarding work, in a non relativistic framework. But classical thermodynamics does not "need" statistical mechanics to be formulated, anymore that it need's Fourier's law of conduction, or Newton's laws of motion, or general relatitivy, or information physics theory. --Crio (talk) 01:18, 25 November 2012 (UTC) Response by Damorbel Crio I have previously explained to Chjoaygame what I am arguing as the nature of heat: From what you write above (...your idea that heat is the energy of vibrating particles...) I understand your argument to be that heat is not the energy of vibrating particles, OK? In that case would you care to explain what you accept as the proper name for the kinetic energy in vibrating or colliding particles? This is not a trivial question because it is some of this kinetic energy that is transferred between material at different temperatures. It is entirely necessary that this energy is preserved, in one form or another, during and after the transfer; were this not so the 1st law of thermodynamics would not be valid ( 28 September 2012 (UTC)) I am arguing that Kinetic theory, as extended to solids by phonons, is the only sucessful theory at the base of thermodynamics and statistical mechanics. Am I wrong? If you think I'm wrong, would you care to say where? --Damorbel (talk) 07:45, 25 November 2012 (UTC) Comment by Crio 'Heat', in a classical thermodynamic explanation of it, does not require a mechanistic explanation of either the system nor 'heat transfer'. Classical thermodynamics do not require, in principle, mechanistic explanations for it's formulation. Statistical mechanics provide _a_ framework that_explains_ (mechanistically) what does happen with _some_ of the internal energy of a 'body' and what does happen where conduction occurs. Radiation is exlained (mechanistically) in the terms of electromagnetic radiation. These two are forms of 'heat transfer', one explained by 'statistical mechanics' (conduction) the other by electromagnetic radiation (radiation). When one deals with turbulence in a fluid there are other complications: gases _do_ have a conductive heat transfer coefficient and, for specific transfer phenomena, different convective heat transfer coefficients, which are related through Nusselt's number. Nusselt's number is a function of Reynolds number and Prandtl number. The main problem of turbulent flow, specially in compressible fluids, is the lack of a proper mathematical framework that is _usable_ (since the existence and smoothness of Navier Stokes has not even been proven). There are other issues that arise with the modelling of 'heat' and 'internal energy' of systems when gravitational phenomena and 'gravitational waves' are taken into account, when dealing with 'informational physics' 'black holes' 'quantum theory' other mechanistic relations regarding thermodynamics arise. One interesting thing is that (from what I understand) some of these mechanistical interpretations of entropy and other quantities are compatible (entropy in statistical mechanics, Von Neumann's entropy, Shannon's entropy). Other's might not be compatible as the general theory of relativity has not been 'unified' with quantum mechanics. Thus entropy in regard to gravitational waves or black holes might not be (as of yet) related to entropy ina quantum mechanics. Still, one can see that the laws of thermodynamics are used without regard of the internal mechanics of the system, the mechanism of heat transfer or the mechanism for doing work. The concepual framework of thermodynamics is more abstract than that. --Crio de la Paz (talk) 15:19, 25 November 2012 (UTC) But, I _do_ agree that, as far as mechanisms to explain classical thermodynamics go, for a mayority of cases (cases that do not deal with gravitational waves or black holes and those kind of things), statistical mechanics is fundamental and of great importance, since it derives macro thermodynamic formulations from the atomic structure of matter. This is _remarkable_. But there is also the concept of entropy in information theory and in informational physics which might be another example of a physical theory that is compatible with classical thermodynamics. Classsical thermodynamics theory seems to hold in regard to the atomic structure of matter (statistical mechanics), quantum theory (Von Neumann's entropy), information theory (Shannon's entropy), and, as far as I understand, the general theory of relativity (gravitational waves and the entropy of gravitational fields). I agree with Darmobel in that the kinetic theory of gases, solids and liquids (including phonons)is a fundamental development that explains a lot of the phenomena studied in classical thermodynamics and heat transfer. But I do think he is wrong stating it is "the only theory" since, i.e. Shanon's model of informational entropy is compatible with thermodynamics too (and with statistical mechanics, in as much as I know). There are also theories of entropy related to the gravitational field (where this is the predominant form) and gravitational waves, as far as I know. Now as per the question of what is the kinetic energy of the particles that constitute a system: it is 'thermal energy' or (part of) the 'internal energy' of the 'system' (not 'heat'). The internal energy of the system includes all forms of energy of the system that do not include energy related to moving the system as a whole (kinetic energy of the whole system) nor the potential energy of the system implied in it's position in a force field. Darmobel seems to state that in a physical process, what is dubbed above, by me, as 'thermal energy' _has_ to be conserved. This is wrong: it is not an specific "form" of energy that is conserved, is energy as a whole. If there is a chemical reaction within the system that releases heat and rises the temperature of the system, thermal energy`is "created". So 'thermal energy' is not conserved: total energy for an isolated system is conserved. To clearify: Darmobel states above: " From what you write above (...your idea that heat is the energy of vibrating particles...) I understand your argument to be that heat is not the energy of vibrating particles, OK? In that case would you care to explain what you accept as the proper name for the kinetic energy in vibrating or colliding particles? This is not a trivial question because it is some of this kinetic energy that is transferred between material at different temperatures. It is entirely necessary that this energy is preserved, in one form or another, during and after the transfer; were this not so the 1st law of thermodynamics would not be valid " Heat is _not_ the energy of vibrating particles. The energy of the vibrating particles of the system is 'thermal energy'. 'Thermal energy' is part of the 'internal energy' of a system. Total energy is conserved, not 'thermal energy'. 'Internal energy' includes all forms of energy contained in a system, but it does not contain the kinetic energy of the system as a whole nor it's potential energy as a whole system in the presence of a force field. It does contain 'thermal energy', but also 'chemical energy', 'nuclear energy', energy related to the formation of Van der Waals interactions, hydrogen bonds, etc. Even when the system is considered to expand one must make room for the pressure related work to make room for the substance and enthalpy comes into play. When (some) of the energy of a system is dispersed as heat and only heat it is true that energy is conserved and, thus, all energy exchanged is used as 'heat' and there is no work production. But when a system does _work_ there is always _some_ energy that is dispersed as heat, no matter if the energy is 'thermal energy' or 'electrical energy' or 'chemical energy'. The concepts of 'heat' and 'work' and the first and second laws of thermodynamics deal mostly to the ammount of energy that _must_ be rejected as heat in order to change a system from one state to the other. ΔETOT=0 for an isolated system. dE=δQ+δW. dS>=δQrev/T For a reversible (ideal) process dE=TdS+δW δW=dE-TdS So the ammount of work avaiable for an ideal process of maximum efficiency is dE-TdS because there is a minimal ammount of energy that _must_be dispersed as heat. Of course a molecular explanation of conductive heat transfer involves kinetic energy of the particles involved. In the case of radiation it is electromagnetic waves and photon exchange which explains how heat is tranfered (so, in this case, 'heat' is _not_ the kinetic energy of the particles involved at all...) The case for convection is more complex and solutions for problems are expresed via dimensional annalysis since modelling turbulent flow, specially for compressible fluids, is not something easily done (Navier Stokes smoothness and continuity have not even been proved yet, and they are not solvable in a lot of cases, with any practicallity). Energy and entropy related to gravitational waves must also be considered. I do believe that explaining conductive heat transfer with the kinetic theory is similar to explaining electrical work via the electrical field. It explains an specific form of 'heat transfer' but not all of them. And in a similar fashion the general theory of relativity is not compatible with non gravitational forces of nature in it's formulations, in as much as I undertand ,since no grand unified theory is amongst us. --Crio de la Paz (talk) 05:25, 26 November 2012 (UTC) Crio you write above:- Heat is _not_ the energy of vibrating particles. The energy of the vibrating particles of the system is 'thermal energy'. This is not correct. Heat is energy with a temperature - the basis of the 2nd law of thermodynamics. Thermal energy is all kinetic energy above zero K; the distinction is subtle but, because of the 2nd law requirement, scientifically and practically very important indeed. --Damorbel (talk) 06:32, 26 November 2012 (UTC) No: Darmobel is _completely_ wrong in this last statement. heat _is_not_ 'energy with temperature'. The second law of thermodynamics does not state this. The second law of thermodynamics states that, when using energy to do work, some energy is always transfered that does not do work. This ammount of energy transfered that does not do work is what is called 'heat'. Alternatively a quantity called 'entropy' is introduced as a function of state such as dS=δQrev/T. For an isolated system ΔS>=0 for any given process. Alternatively permetual motion machines of the second kind: that is there is _not_ a machine _in_the_unvierse_ that transforms energy into work without releasing 'heat'. Nowhere in the source provided by Darmobel does it say this afirmation of his that 'heat is energy with temperature'. Darmobel insist in confussing thermal energy with heat. He should take a basic course in thermodynamics. --Crio de la Paz (talk) 23:21, 26 November 2012 (UTC) first paragraph of the lead See my edit comments. In addition to what I wrote there, heat transfer by radiation, conduction, and convection all involve mass transfer in the literal sense that the object being heated will end up being slightly more massive than it was. So "closed system" is misleading both to lay readers and as a matter of fact (not to mention that it does not appear in the definition of heat given in Reif, the source for that sentence). As for "purely", if we include that term we need to explain what is meant by it - namely, that heat is not work. Otherwise, it clashes with the next sentence. Waleswatcher (talk) 01:51, 27 November 2012 (UTC) closed systems Indeed the word 'closed' does not appear in the particular sentence of Reif to which you refer, nor indeed in the relevant section. But the context and full meaning of the sentence to which you refer are for closed systems. Reif writes: "Let us now consider two macroscopic systems A and A′ which can interact with each other so that they can exchange energy. ... The first kind of interaction is that where the external parameters of the system remain unchanged. This represents the case of purely ″thermal interaction″." Reif is talking about closed systems. Wikipedia entry that cites him should reflect this because it is important here. You are right to use the term 'body' here, I think.Chjoaygame (talk) 02:16, 27 November 2012 (UTC) Closed is correct, anyway. "Closed" means no matter transfer, not no mass-energy transfer. The last (no kind of transfer) is called an "isolated system." Closed systems go up (or down) in mass as they go up or down in energy (since mass is energy), but neither of these things happens as a result of a gain or loss in matter. Matter and mass are not the same thing, and this causes great confusion in relativity theory teaching. Matter (a poorly defined word, but usually means particles with rest mass) is not conserved. But mass is conserved. Mass and matter are equivalent to energy, but while all energy is mass (and has mass), not all energy is matter. Energy transmitted by heat is a good example-- mass goes with it, but matter does not. SBHarris 02:22, 27 November 2012 (UTC) conduction of heat in metals Conduction of heat in metals can occur through electrons, which are matter by any definition. In any case, such distinctions are far too subtle for the first sentence of a wiki article. "Exchange of energy between closed system" is a very confusing phrase, and gains nothing in terms of accuracy. Waleswatcher (talk) 02:30, 27 November 2012 (UTC) Yes, but the total number of electrons in the metal that is your "system" stays the same, even if some go in and others go out. So nobody cares, as one electron is pretty much like another. The point is not so much that matter is allowed in or out, but whether NET matter is allowed in or out (number of each kind of atom or particles changes). The reason we specify a closed system is the first law of thermodynamics demands it if you state that law in terms of only two RHS terms (work and heat). If you use the first law form that says dU = dq + dw (pretend I put in the deltas) and if you allow net atoms or electrons in or out of your system that has an internal energy U, that changes dU without being either dq or dw, so this equation is wrong. So if you're going to use that equation to define heat, you have to specify "closed". Adding the terms for mass in or out gives you another set of terms, a different equation, and now you have the first law of thermo for open systems, which you've seen with the sigma and the particle numbers and chem potentials, etc. If you want to know how an electric current into and out of your system counts, most texts define this as a sort of "work" (it's potential*dC) where C is the charge that goes in and comes out with DC, or the charge that wiggles back and forth in AC. By the way, "convection" doesn't necessessarily require an open system, since heat may be transfered into and out of your system to the surroundings by diffusion, even in convection. Mass moves (is advected) in the surroundings. If you want to analyze energy tranfer within the fluid plume, only then are you looking at an open sytem. As far as the system transfering heat to the fluid, that can remain closed in analysis. SBHarris 03:49, 27 November 2012 (UTC) It improves communication and saves time to carefully specify the formalism one intends. Electric current carried by electrons can be considered as a whole discrete body macroscopic process, when one may think of it as doing work. Or it can be considered at a phase boundary, or in a continuous medium, or both at once, when it is connected with the Seebeck and Thomson and Peltier effects. Considerations like this apply also to convection.Chjoaygame (talk) 05:31, 27 November 2012 (UTC) Okay, here's a problem that is fun. We stick one electrode in an object or even a person on an insulated stand, and ground the other. Now we connect them to a potential, letting their own self capacitance allow them to take a one-way current and build up a charge. Open system. How does their 1/2CV^2 energy compare with internal energy change just from gaining net electrons? And to what potential would you need to charge them before the two kinds of net internal E increase are comparable? Hint--it's comparable to e rest energy in eV. A reminder of how important closing the system is. SBHarris 07:14, 27 November 2012 (UTC) Okay, here's another problem that is fun: guess what I'm thinking?Chjoaygame (talk) 08:39, 27 November 2012 (UTC) Actually for an _open_ system we have a balance of energy of the form: dEk/dt+dEp/t+dU/dt=SUM(mi(Hi+vi^2/2+gzi))+q+w Where: dEk/dt is the increase of kinematic energy of the system, Dep/Dt is the increase of the potential energy of the system and dU/dt is the increase of the internal energy of the system through time. This has to be equal to the sumatory of the enthalpies, kinetic energy and potential energy of the flows of matter into and out of the system, plus the net heat flow into the system plus the net work done on the system . mi is flow of matter "i", Hi it's enthalpy by unit of mass, vi it's velocity and zi it's position in a gravitational field (this can be even generalized more if it is allowed for potential energies that are not gravitational: in that case these potential energies must be taken into account). Of course q might be decomposed in different 'heat flows' either involving differents forms of heat transfer or and w in different forms of power done on the system or done by the system. The important aspect for a conservation law is that the rate at which a given quantity varies for the system is equal to the net flows of the quantity plus net generation of the quantity within the system (this is useful for, i.e., a balance of mass of an specific susbstance in the mist of a chemical reaction. As some oher users have pointed above entropy is another quantity that, for all processes that are not 'reversible' or 'ideal' actually might be 'generated' as far as I understand. --Crio de la Paz (talk) 22:51, 27 November 2012 (UTC) matter Just in case, the article on matter on the wiki says " Matter is generally considered to be a substance (often a particle) that has rest mass and (usually) also volume.". It also states (correctly ) that "Albert Einstein showed[4] that ultimately all matter is capable of being converted to energy, by the formula: $E=mc^{2}\,\!$ where E is the energy of a piece of matter of mass m, times c2 the speed of light squared" Also "An example is positrons and electrons (matter) which may transform into photons (non-matter). However, although matter may be created or destroyed in such processes, neither the quantity of mass or energy change during the process". But, also, it says "Scientifically, the term "mass" is well-defined, but the term "matter" is not. For this reason, none of the uses of the word "matter" in this article should be considered definitive.". And then "Matter therefore is anything that contributes to the energy–momentum of a system, that is, anything that is not purely gravity.[17][18] This view is commonly held in fields that deal with general relativity such as cosmology". There is also the concept of "strange matter", "antimatter", "dark matter", and "dark energy", that complicate matters even more.--Crio de la Paz (talk) 16:21, 27 November 2012 (UTC) Particle physicists tend to define "matter" as the fermions of the standard model, with the possible exception of neutrinos. So that includes electrons, muons, etc. and composites like the proton and neutron, but not for instance the W and Z bosons (even though they're massive) or the photon. Anyway, a system that allows electrons to flow in or out is obviously not "closed" by any sensible definition. If in some specific process the net flow of electrons is close to zero one can ignore the chemical potential terms, but calling such a system "closed" is very confusing, and I think we should avoid using the term in this article. Instead, we can simply explain that energy is conserved, and net matter flowing in or out contributes to the energy balance, which is hence simplest when the net flow is zero. Waleswatcher (talk) 16:52, 27 November 2012 (UTC) Waleswatcher writes: "Anyway, a system that allows electrons to flow in or out is obviously not ″closed″ by any sensible definition", and "calling such a system ″closed″ is very confusing, and I think we should avoid using the term in this article. Instead, we can simply explain that energy is conserved, and net matter flowing in or out contributes to the energy balance, which is hence simplest when the net flow is zero." Thermodynamicists are not in general particle physicists, and this article is more about thermodynamics than about particle physics. Thermodynamicists may not use a "sensible definition", but for purposes like the present they often regard the flow of electricity as just that, without concern about whether particles carry it, and do not regard it as flow of matter; I have not noticed any confusion arising from this.Chjoaygame (talk) 17:23, 27 November 2012 (UTC) Anyway, I agree with Waleswatcher that the word 'body' is convenient here. It did not strike me that SBHarris disagreed with that usage. I had the impression that he was just confirming that Reif and K & K are talking about closed systems, not that he was trying to insist on those very words 'closed system'?Chjoaygame (talk) 17:51, 27 November 2012 (UTC) purely thermal interaction Waleswatcher writes: "As for ″purely″, if we include that term we need to explain what is meant by it - namely, that heat is not work. Otherwise, it clashes with the next sentence." Indeed, otherwise, it clashes with the next sentence. "Purely" is repeated by Reif and is important for his presentation. It is also implicit in that of K & K.Chjoaygame (talk) 03:05, 27 November 2012 (UTC).