Talk:Heat: Difference between revisions
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--[[User:Crio de la paz|Crio de la Paz]] ([[User talk:Crio de la paz|talk]]) 03:29, 22 November 2012 (UTC) |
--[[User:Crio de la paz|Crio de la Paz]] ([[User talk:Crio de la paz|talk]]) 03:29, 22 November 2012 (UTC) |
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Another thing: most probably what will happen in most "heat pumps" at "both ends" would not be "thermal difussion" or "conduction" but "convection". |
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Cheers!--[[User:Crio de la paz|Crio de la Paz]] ([[User talk:Crio de la paz|talk]]) 03:31, 22 November 2012 (UTC) |
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== Boltzmann constant == |
== Boltzmann constant == |
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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
egouser 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."[1]
- 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."[2]
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 = 1/2kBT?
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 98.4oF? --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)
- 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 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 ? That is to say: NA = R/kB. You make it worse by not recognising that your k (= kB) 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)
where (including the SI units)
: is the amount of heat transferred per unit time (in W) and |
: 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)
naughty, naughtyI 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 editsI 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)
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 articleIt 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)
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 mechanicsThermodynamics 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:
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:
Addendum of text quotes for the benefit of DamorbelAdkins (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
further response by Damorbel
repsonse by editor 186.32.17.47I 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 heatThere 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 WaleswatcherWhat 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)
response by Waleswatcher
response by Damorbel
response by DamorbelConvection 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)
response by editor 186.32.17.47Heat 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:-
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)
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)
"However, if the unit of heat is the Joule - section 2/ (energy - conserved)
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)
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)
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)
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)
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 : 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 requirementsEditor 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)
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.
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 DamorbelChjoaygame 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 pazThis 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 SBHarrisNow, 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 CrioSBharris: 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)
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)
Cheers!--Crio de la Paz (talk) 03:31, 22 November 2012 (UTC) Boltzmann constantCan anybody tell me why the Heat article does not mention of the Boltzmann constant? --Damorbel (talk) 21:44, 21 November 2012 (UTC)
RewordingI did some rewording of the first parragraphs. Please review. Cheers! |
- ^ Partington, J.R. (1949), p. 118.
- ^ Maxwell, J.C. (1871), p. 10.