Talk:First law of thermodynamics

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Contents

Separate article[edit]

I agree with such reunification, on the basis that statistical mechanics defines internal energy as the mean of energy. The averaging is done on the set of microstates of the systemThorinMuglindir 21:51, 4 November 2005 (UTC)

Agree - I was going to do this myself, but Karol was quicker. PAR 00:23, 5 November 2005 (UTC)

Agree - I was tempted to do this myself but feared that there would be some resistance. Cutler 12:26, 6 November 2005 (UTC)

Succinctly[edit]

Hello - your recent edit states:

  • The work exchanged in an adiabatic process depends only on the initial and the final state and not on the details of the process; or,
  • The sum of heat flowing into a system and work done by the system is zero.

Mathematically, the first law is δQ=dU+δW. Mathematically the above two statements amount to the following

  • If δQ=0 then δW is an exact differential or,
  • δQ+δW=0

The first is true, but nowhere near a complete statement of the first law, the second is simply wrong. The sign of δW is wrong, and the dU is missing. PAR 23:06, 7 November 2005 (UTC)

A succinct statement would help this article. I am not particular to the math and a english version of the math would be apreciable to the non-mathemtician reading Wikipedia. I gotta go right now ... but it seem to be related to this article Thermodynamic potentials (from a search) ... I just got your msg, but have not the time to respond in full. Mabey tomarrow .... sincerel,y JDR 22:46, 8 November 2005 (UTC)

Here is the statement from the previous page:

The first law states that the amount of energy added to a thermodynamic system
by heating is equal to the increase in the internal or "stored" energy of the
system plus the amount of energy lost by the system as a result of work done
by the system on its surroundings.

What about this do you think needs improvement so we can fix it. PAR 01:46, 9 November 2005 (UTC)

It's a lil wordy ... a good start and doesn't really need improvement .... I'm not sure if this would be any better, but how about "The amount of energy added to a system is equal to the increase of internal system energy plus energy lost in its surroundings as a result of work done". But if not the prior is good with me ... hopefully someone else can suggest a briefer one. Sincerely, JDR 21:57, 9 November 2005 (UTC) (PS., even this one I did seems a bit word to me ... oh well)

Using your statement, I took a cut at it. PAR 22:09, 9 November 2005 (UTC)

Thanks for the note on my talk ... but I think either the version is good (and why I just indented it a few days ago and didn't change it) ... I don't have any objection to the sentence (just wish I was better @ words to 'condense' it) .... I just wanted something that got the concept out without the math or complicated word ... the main thermodynamic laws page need the statement too (I'll copy it over to the main page; which seems to need to be cleaned up ... mabey something I could take a stab at ...). I saw that you removed "thermodynamic", "or stored", and "work done by the system". I was just thinking that a nice short statement would be good for the article. The sentence is hard to cut down without losing needed parts. As I said before, mabey someone else will suggest a better one (though I think this doesn't get much attention; eg., trying to give laymen tersm to technical articles) ... but it may be "good enough". Sincerely, JDR

Negative work: on or by the system?[edit]

The statement in this section that the common convention in Physics is  \Delta U = Q-W is simple wrong. To quote authority Feynman, Landau and Liftshitz and Callen all use \Delta U = Q+W. This is by far the most common convention, and since this is a physics article I propose changing the convention of the article to match the mainstream of physics. Nonsuch 22:46, 24 February 2006 (UTC)

As far as I know, Callen is the best authority, with Landau and Lifshitz high on the list. If they use the plus sign, then I am in favor of using it. Lets be sure and keep it as dU = \delta Q+\delta W using "d" and "\delta" to differentiate between the exact differential and inexact differential. PAR 00:19, 25 February 2006 (UTC)
In the IUPAC pages, one convention is used here: http://www.iupac.org/didac/Didac%20Eng/Didac01/Content/T02.htm when it explicitly states dU = \delta Q+\delta W and then the other convention is used here: http://www.iupac.org/didac/Didac%20Eng/Didac01/Content/T12%20-%20T13%20-%20T14.htm in an actual problem that concludes with the common statement that W=Q (not -Q) for motors. The wikipedia article right now is confusing. One convention is stated once as "the usual", then the other convention is stated twice and applied to open systems. Flying Jazz 17:04, 26 February 2006 (UTC)

To me this section could be deleted entirely. There is already too much fluff in this article which obscures the physical basis of the first law completely. I would actually delete everything from the first equation to the math section but maybe it can be cleaned up.152.1.22.105 20:38, 3 March 2006 (UTC)

I think someone changed the law to the formula  \Delta U = Q+W which is fine, but then W is now the work done on the system, not by the system. —Preceding unsigned comment added by 128.230.72.229 (talk) 21:21, 26 March 2008 (UTC)

A note on notation[edit]

Many modern textbooks use upper case for internal energy and lower case for heat and work. This leads to equations such as dU = δq + δw. An instructor can use this notation (with care!) to emphasize that two different types of properties are being represented (state and path). -- Astrochemist 03:34, 15 September 2006 (UTC)

Bank account analogy[edit]

"As an analogy, if heat were money, then we could say that any change in our savings (dU) is equal to the money we put in (δQ) minus the money we spend (δW)."

Problems with this:

  • We could just as easily switched the money put in and the money spent, which renders our choice of concepts (spending and spending) vacuous.
  • We are using the definition utilizing a plus sign for δW and a minus in the analogy.

The analogy doesn't have to be perfect, but this will only confuse the laypersons which the analogy is supposed to make the article more accessible to. Maybe, we could change δW to interest, but then again that can't be negative. If there no objections, I'm removing this.Loodog 20:41, 17 July 2006 (UTC)

I think an analogy is a nice idea - shame the current one is appalling! LeBofSportif 20:51, 17 July 2006 (UTC)

You could also try this for the dU = δQ + δW sign convention: There are two ways for your bank account's balance (U) to be changed, legal methods (δQ) and illegal methods (δW). Whenever money comes in, you regard the change as positive, reflecting an increase in the balance. Whenever money is removed from your account, either by writing a check (legal, therefore δQ) or bank robbery (illegal, therefore δW) then it's a reduction to your account. Not perfect, I admit. There's no particular reason for associating "legal" with either δQ or δW, so take your pick as to which is used. -- Astrochemist 03:28, 15 September 2006 (UTC)

Article is a total mess (regarding the sign of work)[edit]

Yes, I know this is a valid argument and each field uses its own peculiar variation of work depending upon the system it is studying; however, this is the first law of thermodynamics, not the first law of physics. According to Amazon.com book sales, the top three thermodynamics books used are (#1) Cengel (2006), (#2) Van Ness (1969), and (#3) Fermi (1936); they all use ∆U = Q – W. According to Van Ness: “The equation is usually written in this form. The reason is that it is just an historical accident of history. The first applications of thermodynamics were made on heat engines, devices which take in heat and put out work.” I am going to give this article a quick clean and please simply use side notes in the article if you have an issue regarding how signs are used in each respective field or book. Later: --Sadi Carnot 00:25, 26 July 2006 (UTC)

Cut parts (temporally)[edit]

Essentially, the First Law of Thermodynamics declares that energy is conserved for a closed system, with heat and work being the forms of energy transfer. Heat is a process which transfers energy as a result of a temperature difference between a system and its surroundings. Mechanical work is the product of the force acting on a system and the distance moved in the direction of the force. However, work input can produce a temperature rise that is a mechanical equivalent of heat.

As an analogy, if heat were money, then we could say that any change in our savings (\mathrm{d}U) is equal to the money we put in (\delta Q) minus the money we spend (\delta W).

The δ's before the heat and work terms are used to indicate that they describe an increment of energy which is to be interpreted somewhat differently than the \mathrm{d}U increment of internal energy. In mathematical terms, heat and work are not exact differentials. Work and heat are processes which add or subtract energy, while the internal energy U is a particular form of energy associated with the system. Thus the term "heat energy" for \delta Q means "that amount of energy added as the result of heating" rather than referring to a particular form of energy. Likewise, the term "work energy" for \delta W means "that amount of energy added as the result of work". The most significant result of this distinction is the fact that one can clearly state the amount of internal energy possessed by a thermodynamic system, but one cannot tell how much energy has flowed into or out of the system as a result of its being heated or cooled, nor as the result of work being performed on or by the system.

After cleaning up and re-organizing the article these are the parts cut-out; if someone wants to re-insert parts of these, without duplicating anything, please do so.--Sadi Carnot 00:56, 26 July 2006 (UTC)

Sign convention in relation to Gibbs free energy[edit]

Moreover, the historical sign convention is the standard form used to define and derive the Gibbs free energy equation. Starting from the first law, and neglecting differential details:

dU = dQ - dW\,

From the second law we have:

dS = dQ/T\,

Hence:

dQ = TdS\,

By substituting this into the first law, we have:

dU = TdS - dW\,

Rearranging we have:

dU + dW - TdS = 0\,

Letting dW be pressure-volume work, we have:

dU + PdV - TdS = 0\,

By assigning the quantity to the left of the equals sign the symbol G, as Willard Gibbs did in 1876, this reduces to the following at thermodynamic equilibrium:

dG = 0\,

Or for a spontaneous process:

dG \le 0\,

Thus, this expression is referred to by many as the combined law of thermodynamics; Gibbs showed that deviations of this quantity could be used to predict the direction of various natural chemical processes. The other sign convention doesn't facilitate this derivation.--Sadi Carnot 18:41, 26 July 2006 (UTC)

What were the experiments from Joule that contributed to this law?[edit]

"It was Jame Joule, sho first laid down the foundation of The First Law Of Thermodynamics, saying that The Heat and Work are mutually convertible through his extraordinary series of experiments."

The word "extraordinary" would entice readers to question what were these "experiments". The article should at least include one or two experiments into this sentence such that it would say:

"...through his extraordinary series of experiments such as [experiment 1] and [experiment 2]".

Joule Paddle Wheel experiment is certainly a famous one, but I can't be bothered to do sufficient research to make a worthy edit. Perhaps someone wants to look it up. It may even have a wiki article already. LeBofSportif 16:32, 7 November 2006 (UTC)

As far as I know, Julius_Robert_von_Mayer was the first (1842) who postulated the conservation of energy principle. Beeing a physician and not a physicist, he couldn't express and publish his idea according to the scientific standards of his time. Five years later Hermann_von_Helmholtz refined the first law of thermodynamic and disseminated the news. --Gunnar.Kaestle 11:04, 4 January 2007 (UTC)

Proof[edit]

Why is there no section on the proof of the first law? Is there no such proof or is it horrendously complicated? If the latter, could someone provide an overview for it on the article explaining from what principles the first law is derived? --Kick the cat 09:00, 9 July 2007 (UTC)

It's a three-month-old comment, but I'll answer anyway. There is no proof for the FLoT or any other fundamental physical law. They are axioms that are derived from observation and testing. Crabula 15:26, 11 October 2007 (UTC)

So, in all the observations and testings by man so far in the material physical universe of his access by actual contacts or by concepts in his mind, the socalled first law of thermodynamics has worked;but man has not really or exhaustively performed all the observations and testings that are possible in the totality of time and space of the material physical universe.

Wherefore, the first law of thermodynamics is a convention of man's thinking; but it works in the environment of the material physical universe where man has access and does his activities of manipulating material physical things, and also manipulating concepts in his mind which concepts need not have any correspondence to realities outside his mind. 112.198.79.207 (talk) 18:16, 3 July 2011 (UTC)Yrreg

Editor 112.198.79.207 is commenting on the question of the article's proof or lack of proof of the first law of thermodynamics. The article contains a section Evidence for the first law of thermodynamics. The section is very far from perfect, and needs more work. The comment of Editor 112.198.79.207 is on the philosophical side and it is not clear that he is directly commenting on the section Evidence for the first law of thermodynamics. If Editor 112.198.79.207 is interested in a detailed history of the discovery or proof of the first law, he may find it useful to read the reference given in the article to the carefully researched 1980 book of Truesdell, The Tragicomical History ..., though he may find that book rather too detailed.Chjoaygame (talk) 20:16, 3 July 2011 (UTC)

First section of article seems wrong[edit]

The first section (about everyone being wrong as to their perception of what the first law of thermodynamics is) seems wrong to me, as a quick google search has produced a lot of evidence of the supposedly "wrong" version being correct and zero evidence that it is incorrect. Joeedh (talk) 07:03, 14 March 2008 (UTC)

Sign convention (march 2008)[edit]

I have edited the article so it is internally consistent. It now reads dU = dQ-dW. with the work term being work done by the system. My personal preference is dQ+dW but consistency is much more important. If any vigilante wants to revert back, discuss here first.

I have also removed the bank account analogy because I don't feel it was helpful. LeBofSportif (talk) 21:46, 26 March 2008 (UTC)

Sin convention - need source for this idea.[edit]

My professor told the class that the reason the equation was original made with a "-" was because engineers back then wanted to make the numbers with what you put "in" and "out" both be positive, such as in locomotives and stuff. —Preceding unsigned comment added by 129.119.149.32 (talk) 23:08, 23 April 2008 (UTC)

Ironic?[edit]

"It is actually the second of four Laws of Thermodynamics, the ironically named "Zeroth Law of Thermodynamics" having been added retroactively."

What exactly is "ironic" about the name of the "Zeroth Law of Thermodynamics"? It would be ironic if the law stated that "zeroth" is not a real word or something to that nature, but as it stands I don't find it very ironic. I'd call this naming convention "odd" or "misleading" at best.

--209.2.224.148 (talk) 05:57, 12 September 2008 (UTC)

History of the law[edit]

it would be interesting to have this in the article, or a link to the article that discusses this. 67.180.144.239 (talk) 05:32, 5 November 2008 (UTC)

Unreferenced[edit]

How can this page be assessed as B-Class when it contains NO references? The first criteria listed in WP:BCLASS is "The article is suitably referenced, with inline citations where necessary." Even a start-class article is supposed to have references. Weakly referenced, but referenced just the same. Killiondude (talk) 20:06, 1 December 2008 (UTC)

Internal energy[edit]

The article states that internal energy is conserved and that

dU=\delta Q-\delta W\,

But isn't this wrong, is it not? If internal energy was conserved, shouldn't dU = 0? -63.226.203.127 (talk) 22:12, 21 January 2009 (UTC)

Alternate description[edit]

"The increase in the internal energy of a system is equal to the amount of energy added by heating the system, minus the amount lost as a result of the work done by the system on its surroundings."

Is this ignoring work put into the system and heat leaving the system? Maybe it should say something about "net work" and "net heat." 63.196.195.215 (talk) 04:37, 14 October 2009 (UTC)

Alternate description[edit]

"The increase in the internal energy of a system is equal to the amount of energy added by heating the system, minus the amount lost as a result of the work done by the system on its surroundings."

Is this ignoring work put into the system and heat leaving the system? Maybe it should say something about "net work" and "net heat." 63.196.195.215 (talk) 04:37, 14 October 2009 (UTC)

Need link or definition for "quasistatically"[edit]

I added this link today.--Llewkcalbyram (talk) 12:45, 7 January 2010 (UTC)

History of the First Law[edit]

There seems to be no history of how the First Law was discovered and/or formulated. Who was behind all this? How did they reach the conclusion? When? This would be an enormously valuable addition to the article it would seem to me. ThePeg (talk) 11:32, 24 January 2010 (UTC)

Article is lacking key aspect[edit]

What is the history of the 1st law? Who proposed it? When did it come into being? How was it formalized? Was it really Hermann Helmholtz [1] or was that simply the first theory of thermodynamics, which was later proven into law by somebody? --Bertrc (talk) 00:27, 23 February 2010 (UTC)


Is it a Law or a Theory? Is there a convincing proof? If a Law, then the Big Bang Theory is wrong and the Universe is infinite in time and space.

Sign convention April 2010[edit]

I would really like to know which disciplines use which sign conventions for work. I have a physics textbook by Daniel Schroeder that states:

"Many physics and engineering text define W to be positive when work-energy leaves the system rather than enters. The equation 1.24 instead reads delta U = Q- W. This is convenient when dealing with heat engines, but I find it confusing in other situations. My sign convention is consistently followed by chemists, and seems to be catching on among physicists."

Is that true? I, as a physicist, am used to W as work done on. What do chemists use this as well?--Louiedog (talk) 15:09, 29 April 2010 (UTC)

delta U = Q - W is not going to change anytime soon in physics textbooks. When it is more convenient to to have a plus sign in here, one can define another symbol for the work done on the system to distinguish that from work done by the system. This is what F. Reif does in his textbook whenever he wants to focus on work done on the system. So, you can just define
W' = -W and then write dU = Q + W'. Count Iblis (talk) 15:22, 29 April 2010 (UTC)

Original version of the first Law[edit]

I think that the First Law, as is stated here, is incomplete, since it relies in separate means of calculate work and heat, that are not defined. Work can be calculated extending the mechanical definition of work, to electrical, gravitational, or chemical ones, for instance. However, heat is often calculated using this version of the first law, that then becomes void of physical meaning, serving as a mean to calculate the value of heat.

I would suggest, following Atkins excellent explanation in "Four Laws that drive the Universe" (ISBN:0199232369) or Çengel "Thermodynamics" (ISBN:0071257713), to use Clausisus original statement:

For all adiabatic processes between two specified states of a closed system, the net work done is the same regardless of the nature of the closed system and the details of the process.

that contains the physical content of affirming the existence of a state function (the internal energy) even when work depends on the path in general, in the same way that the zeroth law defines temperature. Later on, the expression can be extended to include non-adiabatic processes, from

Q = \Delta U - W=W^\mathrm{ad}-W\,

where the increment in the internal energy has been already defined by the first law.Gonfer (talk) 09:33, 20 May 2010 (UTC)

We could have a separate section explaining the definitions in classical thermodynamics. Thing is that today in physics we typically don't base thermodynamics on classical thermodynamics anymore.
As you point, this is the current approach in physics (that said, I am a physicist and I was taught classical thermodynamics prior to statistical physics). But thermodynamics is very important for chemists and engineers too. As a physics teacher in first courses in a engineering school, I find classical thermodynamics easier to understand and more general than statistical thermodynamics (since except for ideal gases or perfect crystals the discussion in terms of microstates and collectives becomes too complicated). For engineers, a discussion in terms of thermal machines and efficiencies is much clearer and related to their experience.
Is the same with entropy, I know that it is easily explained in terms of k lnw, but for an engineer is better interpreted in terms of lost work and irreversibilities.
In any case, neither the statistical nor the Clausius original statement are used in this wikipedia article to express the First Law, that seems incomplete from my point of view.Gonfer (talk) 07:43, 21 May 2010 (UTC)
The modern point of view is based on statistical mechanics. So, we have the laws of quantum mechanics and then we already know that energy is conserved. Thermodynamics arises as a coarse grained description of a system with a huge number of degrees of freedom by averaging out the microscopic degrees of freedom.
In this description you explicitely keep track of a few variables (the so-called external parameters) while all the other variables that have been averaged out are described statistically. Work is then by definition the change in energy due to the change in external parameters, heat is everything else. Count Iblis (talk) 14:01, 20 May 2010 (UTC)

First law of thermodynamics is about thermodynamics[edit]

No doubt that the first law of thermodynamics observes the principle of conservation of energy, as noted in the third sentence of the lead; but the two are distinct. The first law of thermodynamics is about thermodynamics, while the law of conservation of energy does not specifically refer to the distinction between work transfer and heat transfer, a distinction which is of the essence of thermodynamics. The one reference to a web page that was given for the new edit does not match the eleven references to authoritative texts on thermodynamics that supported the previous and now restored version. And indeed the web page given as a reference supports the previous and now restored version, not the new edit: it starts "Thermodynamics is the study of systems involving energy in the form of heat and work." The webpage is however defective in that it does not at that point observe that heat and work are forms of transfer of energy, not forms of energy as such; the distinction matters.Chjoaygame (talk) 21:18, 11 August 2011 (UTC)

meaning of edit[edit]

I think that the previous edit was meaningful and useful. Energy is an abstraction if ever there was one. Its non-uniqueness is part of the meaning of that. One can measure the length of a rod, and there is no arbitrary zero adjustment for that; the length of a rod is a more concrete, less abstract and less purely mathematical, quantity, than the energy of a system. I agree that it is useful, as you suggest, to note that the arbitrary constant is an additive one.Chjoaygame (talk) 23:52, 11 August 2011 (UTC)

But then we do have to note that this is not the case in General Relativity. The vacuum energy appears as a cosmological constant term. Suppose that term is zero but you decide to redefine the zero point of the energy, so that the vacuum now has non-zero energy, you would have to include a fictitious cosmological constant term to compensate for that.
Of course, General Relativity is not the first thing one thinks about in thermodynamics. But then the study of the early universe is heavily based on thermodynamics, so we should get this right. Count Iblis (talk) 14:52, 12 August 2011 (UTC)
To consistently present or to derive thermodynamics from a presupposed perspective of general relativistic thinking would make an article on thermodynamics more or less inaccessible to very many readers. Perhaps a new and separate article on general relativistic thermodynamics would be a convenient way to go ahead: such a new article would make sense to those readers who already understand general relativity, while those who do not could get the basics of thermodynamics from the present article.Chjoaygame (talk) 21:00, 12 August 2011 (UTC)

The new edit of 02:31, 15 August 2011, by 128.220.160.6 is still not right; indeed it is worse than before. Editor 128.220.160.6 seems to want to promulgate an ultra-simple statement of the first law, but this Wikipedia article is not the place for him to do it. His new effort is so vague as to be nearly meaningless. He says he was requested to state the law without referring to energy; no, he wasn't.Chjoaygame (talk) 07:08, 15 August 2011 (UTC)

edits of editor 128.231.77.217 of 16 August 2011[edit]

The edits of editor 128.231.77.217 of 16 August 2011 are intended to impose a particular point of view that is not supported by the majority of authoritative sources that are cited on the page on this particular point. The physical content of that particular point of view is already stated in the lead of the article. There is a difference and distinction between the first law of thermodynamics and the principle of law of conservation of energy. The particular point of view of editor 128.231.77.217 tries to ignore or by-pass or erase that distinction; if the distinction did not matter then it would come into question whether there should be separate articles about the two subjects first law of thermodynamics and law of conservation of energy.

The editor 128.231.77.217 initially on 11 August 2011 proposed to justify his edit on the grounds that it seemed like an intuitive change. Now he has tried to impose it without engaging in conversation on this page, and without dealing with the many authoritative references on the page that do not support his particular point of view. He has produced one reference that he apparently thinks supports his point of view.

The zeroth law of thermodynamics does not concern transfer of energy as work, but only transfer as heat, and, by contrast, it is material that the first law concerns both. So it is material to state the distinction as an introduction to the statement of the first law, in the context of the zeroth law.

The particular point of view, that is put by editor 128.231.77.217, does not bring attention to the main feature of thermodynamics that it is about the distinction between transfers of energy by heat and by work. So that particular point of view is inferior as a view of a law of thermodynamics. Editor 128.231.77.217 offers no more than his intuition to justify his particular point of view. His particular point of view is not new to this page; it has been dealt with in the past, and is covered already within the article. He has not bothered to say anything about it on this talk page. He is not participating in the edit process in a reasonable way.Chjoaygame (talk) 22:14, 16 August 2011 (UTC)

As a Wikipedia editor, I do not impose points of views. I originally made what I thought was an obvious fix to the article based on text I had just read, but I couldn't remember the source. When that fix was questioned, I tried to reconcile my fix with the questioned content. When that reconciliation attempt was reverted, I found the material that was the original source of my edit. I don't understand how you can disagree with an edit that is restating almost word-for-word the text of a secondary source. It would seem like this is the sort of material that belongs in Wikipedia. I have changed the article to leave my sourced edit in place. If you continue to disagree with the edit, please tell me why the original source cannot be relied on. My edits simply restate information that has already been published, it has the added benefit that it is easy to understand. I find many technical Wikipedia articles could use a good revision based on an undergraduate source textbook, many are simply written to esoterically to be meaningful. 128.231.77.217 (talk) 16:00, 18 August 2011 (UTC)
I showed a colleague your statement, and he was interested in what you thought the difference was between the "difference" and the "distinction" between the first law of thermodynamics and the principle of law of conservation of energy. Thank you. 128.231.77.217 (talk) 16:33, 18 August 2011 (UTC)
Reply to editor 128.231.77.217
Editor 128.231.77.217 has now begun to talk about his proposed edit, but still seems to feel that it is ok simply to overwrite a previous edit without substantial reason.
Editor 128.231.77.217 says "As a Wikipedia editor, I do not impose points of views." But his actions belie his words. He has not made any attempt to justify his edit beyond saying that it fitted a source that he had just read. Apparently he has not taken any notice of the eleven authoritative sources that he was overriding, nor of the presence of his point of view already in the lead which he is editing. Contrary to his words, in effect he is making moves to impose his point of view. He writes "I don't understand how you can disagree with an edit that is restating almost word-for-word the text of a secondary source." It does not seem to occur to him that eleven authoritative sources have a point of view different from his own, and that he should take that into account in his edit, but does not.
Editor 128.231.77.217 makes the trivial, gratuitous, scarcely relevant, and apparently sarcastic remark that "I showed a colleague your statement, and he was interested in what you thought the difference was between the 'difference' and the 'distinction' between the first law of thermodynamics and the principle of law of conservation of energy." But editor 128.231.77.217 does not engage in the substance of the matter.
It does not seem likely to be useful that I should simply revert again the edits of editor 128.231.77.217 of 16 and 18 August 2011, because it seems likely that editor 128.231.77.217 would simply continue with his habit of overwriting without sound reason. I will need to think of some other way of responding.Chjoaygame (talk) 23:41, 18 August 2011 (UTC)

request for other opinions about the very recent edits of editor 128.231.77.217 on this page[edit]

It seems that the appropriate next step for me in this situation is to ask for other opinions on the very recent edits of editor 128.231.77.217 . This entry is my request for such opinions.Chjoaygame (talk) 23:55, 18 August 2011 (UTC)

I'm not sure who is right. To 128.231.77.217 I would say that simply having a reference which supports your point of view does not justify its inclusion in Wikipedia, particularly if there are other references which dispute it. Please read at least some of those references and try to understand their point of view. To Chjoaygame, I would say that the the question of "what is the difference and distinction between conservation of energy and the first law" is a valid question which needs an answer, even if it was asked in a less than perfectly civil way. Can you give me a short description of the distinction mentioned in these other references? PAR (talk) 03:49, 19 August 2011 (UTC)
Thank you for your comment, PAR. The distinction between the first law of thermodynamics and the law of conservation of energy is attested to by the presence of separate articles, rather different from each other, on the two. The article on the law of conservation of energy makes only one small reference to transfer of energy, not about the law itself, but about a consequence of the law; in that article's lead there are the words "A consequence of the law of conservation of energy is that perpetual motion machines can only work perpetually if they deliver no energy to their surroundings", hardly a statement that thermodynamics finds enlightening, since thermodynamics holds that perpetual motion machines cannot physically exist. The rest of the lead of that article is about isolated systems, for which energy transfer is forbidden. There is no mention of heat in the lead to the article on the law of conservation energy. The article on the law of conservation of energy has a section on the first law of thermodynamics which starts with the rather vaguely or loosely worded sentence: "Entropy is a function of a quantity of heat which shows the possibility of conversion of heat into work." Though loosely worded, this sentence immediately makes clear that thermodynamics is about transfer of energy as work or as heat, a distinction not mentioned in the law of conservation of energy.
The difference between the first law of thermodynamics and the law of conservation of energy is that the first law is explicitly about the distinction between energy tranfers as heat and work, while the law of conservation of energy is about energy in general, not focused on energy transfer. Heat is not in general recognized in thermodynamics as a form of energy so much as it is viewed as a form of transfer of energy, particularly by conduction and radiation, which are explicitly forms of transfer of energy. The distinction between the two laws is to be drawn largely from the way in which the laws are stated in the more authoritative texts of thermodynamics: they all state the first law of thermodynamics as is done in the article. Less authoritative texts may cut corners by conflating the two laws, but in doing so they more or less erase the special concern of thermodynamics with heat transfer, which is not a special concern of the law of conservation of energy.
The reference given for his edit by editor 128.231.77.217 is not to a textbook of thermodynamics. It is to a textbook of chemistry, with a molecular approach. Thermodynamics is primarily about the molar as opposed to the molecular approach, and is concerned largely with physical questions not of particular interest to chemists. Thus, whatever view that textbook might put on this matter, it can hardly be claimed to be an authoritative reference about mainstream thermodynamics; it proclaims itself as from a special point of view, that of a molecular approach to chemistry. It will take me some time to find a copy of that reference, which will need to be read reasonably carefully, because a one or two line quote from it may not give a reliable assessment of its position.Chjoaygame (talk) 08:46, 19 August 2011 (UTC)
The reference I provided is the chemistry textbook most often used for introductory and intermediate level chemistry at the undergraduate level. I am interested in hearing your opinion on the statements made in this book. 128.231.77.217 (talk) 21:07, 19 August 2011 (UTC)
Editor 128.231.77.217, I read your comment here. I note that you have so far not offered any reason in thermodynamics in favour of your edit. You have not told us how your reference moves from the general statement about energy to the concept of heat transfer that is at the heart of thermodynamics. You have not responded to the reasons I have given here for the usual point of view that you wish to overwrite. You have not indicated that you have considered the existence of a separate Wikipedia article on the law of conservation of energy, the idea with which you wish to overwrite the article on thermodynamics.
You have now appealed to what, it seems, you think is the the authority of what you think is "the" chemistry textbook most often used for introductory and intermediate level chemistry at the undergraduate level. This identifies your point of view, which has been well represented in the article for some time before your edit, and does not need to be made the overriding viewpoint that you want to make it. Thermodynamics is largely based in physics, and has a long and honourable history, of which so far you have made no mention. You have made no mention of your having consulted any of the eleven authoritative texts that favour the usual view of thermodynamics, that you intend to overwrite with your point of view.
You are now asking for my opinion of statements made in a chemistry textbook that you have cited. Sad to say there is no copy of it in the university library that I usually use. Of the four universities in my town, only one has a copy, and that in a rural campus branch library, 150 km out of my town. I note that the edition that you cite is not the latest edition of Tro's chemistry textbook for students. I cannot precisely predict how long it will take me to get a copy, it being Saturday morning here now. You have not offered evidence in favour of your proposal that the textbook you have cited is "the" textbook of its class.Chjoaygame (talk) 23:01, 19 August 2011 (UTC)

I am still working on access to a copy of "the" chemistry textbook most often used for introductory and intermediate level chemistry at the undergraduate level. In the meantime, I note that no thermodynamic reasoning has appeared in response to my request for opinion on the recent edits of editor 128.231.77.217 to this article on the first law of thermodynamics. May I draw attention to reliable sources that may help anyone wanting to form an opinion on this matter.

One reliable source on thermodynamics is Bailyn, M. (1994). A Survey of Thermodynamics, American Institute of Physics Press, New York, ISBN 0-88318-797-3. On page 79, Bailyn writes of what he calls "the thermodynamic approach" to the first law of thermodynamics, distinguishing it from what he calls the "mechanical approach", used by Caratheodory amongst others. He attributes the "thermodynamic approach" to Clausius. The statements of Clausius are provided in the Wikipedia article on the first law of thermodynamics.

Bailyn devotes a chapter to the distinct natures of heat and of work. In Part D of that chapter, he writes on page 50: "Processes in which heat is not allowed to flow to or from the environment are called adiabatic." Thus Bailyn makes it clear that the concept of adiabatic process takes the physical reality of heat as a presupposition. That is to say, heat is a fundamental element of the concept of adiabatic transfer of energy, and the use of the term adiabatic does not excise the notion of heat from the discussion. Recognition of an adiabatic process requires recognition of heat transfer, for empirical verification of its absence.

Another reliable source on thermodynamics is Planck, M. (1897/1903). Treatise on Thermodynamics, translated by A. Ogg, Longmans, Green & Co., London. Planck in the first sentence of section 55, the lead section of Chapter 1 of Part 2, writes: "The first law of thermodynamics is nothing more than the principle of conservation of energy applied to phenomena involving the production of absorption of heat." Thus Planck distinguishes the principle of conservation of energy from the first law of thermodynamics by the absence of a mention of heat from the statement of the principle of conservation of energy and its presence in statement of the first law of thermodynamics.

The law of conservation of energy is noted (this stood also before the recent edits of editor 128.231.77.217) in the lead to that article in its third and fourth sentences: "The first law of thermodynamics observes the principle of conservation of energy. Energy can be transformed, i.e. changed from one form to another, but cannot be created nor destroyed." Thus the point of view of editor 128.231.77.217 was already well and properly presented in the article as it stood before his recent edits, though it was not presented as the primary viewpoint of the article, as his edit appears to make it.

The recent edits of editor 128.231.77.217 have the effect of appearing to erase the distinction between the first law of thermodynamics and the law of conservation of energy, by erasing the the second part of Planck's sentence quoted just above. This is a confusing and inappropriate move for an article on the first law of thermodynamics, especially when the Wikipedia has also a separate article on the law of conservation of energy, and the existence of the two laws is explicitly mentioned in each article. No thermodynamic reason has been offered here for such a move.Chjoaygame (talk) 00:28, 24 August 2011 (UTC)

The law of conservation of energy is more general than the first law of thermodynamics - the first law is a special case of the law of conservation of energy in that it is specifically involved with the relationship between thermal and mechanical energy. This is a part of the general law of conservation of energy. The law of conservation of energy and the first law should not be combined for this reason. The general law of conservation of energy must be concerned with transfer of energy, obviously. The first law is again, a sub-topic in the discussion of energy transfer. I do not see any aspect of the first law that is "outside" of the general law of conservation of energy, except for the historical path taken to arrive at this realization. (Another reason the two articles must not be combined.) PAR (talk) 02:45, 25 August 2011 (UTC)
Thank you PAR for your care in this.Chjoaygame (talk) 21:16, 25 August 2011 (UTC)

I now have a copy of the source of the edit of editor 128.231.77.217, the first edition of Tro's textbook Chemistry: a Molecular Approach, and am reading it.

I note that my request for opinion about the currently standing edit of editor 128.231.77.217 has not led to more than PAR's very welcome view that the Wikipedia articles on the first law of thermodynamics and on the law of conservation of energy should not be combined, and his very welcome view that the first law of thermodynamics is a special case of the law of conservation of energy. In particular, editor 128.231.77.217 has given no indication of response to my comments about his edit and has given no indication that he has looked at any of the eleven reliable sources which stand against his edit. It has taken me a fortnight to get a copy of the source cited for editor 128.231.77.217's edit; secondhand copies are readily and cheaply available in the United States but not here; I have borrowed it from an interstate university library. But it should be easier to find at least some of the eleven reliable sources because they are standard works that will be in most university libraries.

Therefore I repeat my request for other opinions on the currently standing edit of editor 128.231.77.217, and in particular I would like to ask for some thermodynamic reasons from editor 128.231.77.217, who has offered none so far.Chjoaygame (talk) 20:53, 1 September 2011 (UTC)

Reading of the first edition of Tro's textbook, ISBN 0-13-100065-9, as potentially relevant to this Wikipedia article

The relevant chapter, Chapter 6, of Tro's textbook is headed Thermochemistry. It is directed by a molecular approach to chemistry. It does not advertise itself as a general source for thermodynamics as such. It cites no scientific literature. Without stating any reason, it conflates the first law of thermodynamics with the law of conservation of energy, contrary to the general run of authoritative reliable sources on general thermodynamics. In my view, it is not a reliable source for a Wikipedia article on the first law of thermodynamics.Chjoaygame (talk) 05:15, 2 September 2011 (UTC)

Continuing discussion of the very recent edits of editor 128.231.77.217 Chjoaygame (talk) 23:35, 2 September 2011 (UTC)

Just to be sure, do we agree that the first law is a particular case of the general law of conservation of energy? In other words, the general law includes all forms of energy, including thermal energy, while the first law is a particular case which specifically includes thermal energy. PAR (talk) 16:15, 2 September 2011 (UTC)

Yes, or nearly yes. The first law is a particular case of the general law of conservation of energy. It specifically refers to transfers of energy as heat and as work. The phrase "thermal energy" should be used to refer specifically to transfer of energy, because otherwise it might be hard to define in some circumstances.Chjoaygame (talk) 20:38, 2 September 2011 (UTC)

In theoretical physics, the first law is taken to be the definition of heat, see e.g. the book by F. Reif. The issue here is that from a theoretical POV (as opposed to a practical POV), the distinction between heat and work is completely arbitrary. If you have some arbitrary system and you don't consider any practical limitations, you can choose your external parameters in any way you like. Work is defined as the minus the change in the internal energy due to the change in external parameters, heat is what is left in order to satisfy conservation of energy.

E.g., if you take every degree of freedom inthe system as your external parameters, then the heat is always zero, entropy is always zero and every change in the internal energy is due to work. Count Iblis (talk) 22:52, 2 September 2011 (UTC)

Yes, good point. The first law *defines* heat and internal energy. (internal energy is exactly what I meant by "thermal" energy above). PAR (talk) 00:09, 3 September 2011 (UTC)

Thank you for this opinion, Count Iblis. I see that you make a particular link between the first law of thermodynamics and the concept of heat. I note that the law of conservation of energy does not make such a link explicit. Count Iblis distinguishes the theoretical from the practical. I suppose it is accepted that the first law of thermodynamics has both theoretical and practical aspects.Chjoaygame (talk) 07:14, 4 September 2011 (UTC)

To quote from the conservation of energy article: "A key stage in the development of the modern conservation principle was the demonstration of the mechanical equivalent of heat". PAR (talk) 10:02, 4 September 2011 (UTC)

Request for help from editor 128.231.77.217

I would like to ask editor 128.231.77.217 very kindly to revert his overwrite of the lead sentence of the article on the first law of thermodynamics. I think this would be the best way forward here. As I read the opinions of PAR and of Count Iblis, they would tend to support this request of mine. Editor 128.231.77.217 has not given thermodynamic reasons for his overwrite, and therefore I suppose he may be amenable to my request that he revert his edit.Chjoaygame (talk) 21:44, 6 September 2011 (UTC)

Why don't we try modifying what exists now. Based on the discussion, it appears that the existing text is imperfect but useful. I would like to ask editor Chjoaygame if you could edit the text that exists now. Then we and other editors can edit as we both see fit, building a collaborative document that is better than what was there originally. Isn't that what a WIKI is all about? That seems like the better approach than reverting to a substandard product. Why revert from one substandard sentence to another? It just doesn't seem like a useful exercise. 128.231.77.239 (talk) 14:05, 9 September 2011 (UTC)
Thank you editor 128.231.77.217239 for your comment. I am do not like the plan of just editing over each other, because it is not really collaborative. Collaboration will need some kind of agreement, and that I think is not likely to emerge simply by a process of repeated overwriting. The agreement needs to reflect common understanding, which is more likely to emerge by discussion on this page than by repeated overwriting. I think it better to work on this talk page to make a collaboration.Chjoaygame (talk) 21:15, 9 September 2011 (UTC)

Discussion of lead sentence[edit]

The presently standing version of the first sentence of the lead reads:

The first law of thermodynamics states that energy cannot be created or destroyed.

This version is an overwrite on the previous version, which I would like to restore, which reads:

The first law of thermodynamics refers to thermodynamic processes in which heat and work can be distinguished and measured.

The presently standing version was, in the recent round of edits, initially supported by the following taken by copy and paste from its source at [2]:

The first law of thermodynamics
12-8-99
Sections 15.1 - 15.4
Thermodynamics
Thermodynamics is the study of systems involving energy in the form of heat and work. A good example of a thermodynamic system is gas confined by a piston in a cylinder. If the gas is heated, it will expand, doing work on the piston; this is one example of how a thermodynamic system can do work.
Thermal equilibrium is an important concept in thermodynamics. When two systems are in thermal equilibrium, there is no net heat transfer between them. This occurs when the systems are at the same temperature. In other words, systems at the same temperature will be in thermal equilibrium with each other.
The first law of thermodynamics relates changes in internal energy to heat added to a system and the work done by a system. The first law is simply a conservation of energy equation:

Thus the presently standing version was originally supported by a citation which actually supported the previous version which I would like to restore, not the presently standing version. The original citation would have misled a reader who did not actually check it when he would have found that it did not actually support what it was indicated as supporting.

The previous version of the Wiki article, which I would like to restore, was like, but more informative and accurate than, the lead sentence of the cited webpage, which reads "Thermodynamics is the study of systems involving energy in the form of heat and work." This is because heat and work are kinds of process of energy transfer, not variables of state of systems. The cited webpage sentence has as its most obvious reading that heat and work are variables of state of systems, which is not a good reading; it does not indicate that heat and work refer to processes as distinct from systems; thus the form of expression of the cited webpage tends to support an inaccurate reading, and the previous version of the lead sentence of the Wiki article was better.

The cited webpage did indeed, in its fifth and seventh sentences, observe the transfer character of heat and work. In this respect the cited webpage eventually agrees with the previous version that I would like to restore.

The cited webpage did indeed, in its ninth sentence, mention the law of conservation of energy. By comparison, the previous version of the Wiki article mentioned the law of conservation of energy in its third sentence. Thus, the previous version gave perhaps more emphasis to the law of conservation of energy than did the cited webpage, which was being used support the present version's promotion of emphasis on the law of conservation of energy. Thus the new edit did not have support in this respect from its originally cited source.

The presently standing version of the first sentence of the Wiki article is now supported by a reference to another source, which is specialized in an area other than general thermodynamics. There is actually a serious flaw in the thermodynamics of that other source. The picture of The Bomb Calorimeter in figure 6.6 is utterly wrong. It is being represented as an illustration of constant volume calorimetry, but it is really an illustration of constant pressure calorimetry. The chemical reaction is shown as occurring in a constant volume bomb, and that means that the heat evolved is for a constant volume reaaction. But constant volume calorimetry refers to the calorimetric volume not the reaction volume; thus the figure makes a mistake in the heartland of thermodynamics. Thus the illustration is misleading and indicates the the author was not really focused on thermodynamics as such. After all, he advertises his book as being on chemistry from a molecular approach, not as being about thermodynamics as such, and his chapter heading is Thermochemistry, not Thermodynamics as such, which is specifically about the molar as opposed to the molecular approach. Thus the presently cited source is not a reliable source for the presently standing lead sentence.

The sources for the present Wiki article's often stated version of the first law are eleven. This list of sources is long because the matter is important. Two of them are references to the original statement of the first law, as distinct from previous historical statements that are more or less like the first law but do not exactly state it. There follow seven authoritative sources on general thermodynamics showing continuity over a century of agreement about the statement. The statement by Prigogine and Defay (1954), a textbook of Chemical thermodynamics, takes the viewpoint espoused by the current version of the lead sentence of the Wiki article; this viewpoint is represented in the current version of the Wiki article by a specific reference in its fifth sentence. Accordingly, I will shortly remove that Prigogine and Defay (1945) reference from the list of references for the often stated version of the law. Shortly I will also delete from that list the reference to the 1897/1903 textbook by Helmholtz because it is in German and not readily available to English speakers.Chjoaygame (talk) 22:59, 9 September 2011 (UTC)

I strongly disagree with any opening statement which does not make clear that the first law is a statement of the conservation of energy. I favor the statement of Fermi in "Thermodynamics". The first two sentences in the chapter on the first law reads: - "The first law of thermodynamics is essentially the statement of the principle of the conservation of energy for thermodynamical systems. As such, it may be expressed by stating that the variation in energy of a system during any transformation is equal to the amount of energy that the system receives from its environment". (Energy lost is negative energy gained, of course.) Using words like "refers to" and "study of systems involving" give no indication of the core of the first law, which is conservation of energy. Use of the word "variation" avoids the identification of work and heat with energy. Fermi then goes on to explain that the amount of energy received is equal to the thermal energy acquired by heating and by having work done on the system. PAR (talk) 03:40, 10 September 2011 (UTC)

Thank you PAR for putting your point of view here. You have a special point of view, which, especially in the article on the zeroth law of thermodynamics, you defend and promote vigorously and assiduously, the point of view that derives from the Carathéodory axiomatization of equilibrium thermodynamics, called by Bailyn the "mechanical approach" in contradistinctiom from the "thermodynamic approach". That point of view does not cover the full range of thermodynamics which includes non-equilibrium thermodynamics. And it takes only the 'state' approach to thermodynamics, leaving out the 'process' approach. It is catered for by the third sentence of the article.

To insist, as you seem to want to do, on the opening statement of an article on the first law of thermodynamics carrying the message of the principle of the conservation of energy is to push your particular point of view, so as to emphasize the more general law and to distract attention from the particular law which is actually the subject of the article. Your point of view includes the view that the first law of thermodynamics has a core in the law of conservation of energy. That is not what actually distinguishes the first law of thermodynamics and therefore does not have a preemptive claim to primary emphasis in a neutral article.

The 1936 course of lectures transcribed in the book you cite of Fermi prefaces itself by saying that it is an elementary treatise. The book is guided by notes of the lectures made by Dr Motz. The book assumes that the reader is familiar with the fundamental facts of thermodynamics and calorimetry. That might seem to make it presuppose the notions of temperature and calorimetry. Fermi's book is does not supply literature references. Fermi manages very well without ever mentioning a zeroth law of thermodynamics, and if he were to be regarded as a reliable source on such matters, then we would be looking at ignoring the explicit numbered statement of the zeroth law. True, Fermi was writing perhaps without having read Fowler and Guggenheim's 1936 text which was perhaps the first to state the zeroth law as a numbered law. Fermi is very famous for his work in atomic physics but not so for his scholarship in thermodynamics.

Fermi's book that you cite here has as the first sentence of its introduction: "Thermodynamics is mainly concerned with the transformations of heat into mechanical work and the opposite transformations of mechanical work into heat." True, Fermi says that the first law of thermodynamics is the principle of conservation of energy, and asserts that it was first discovered by Mayer in 1842. But Fermi is not the best source for the history, and in effect he is crediting Mayer with more than is right, giving him precedence over Clausius and Rankine, without mentioning Helmholtz or Hess.

Fermi's first sentence in his chapter on the first law of thermodynamics reads: "The first law of thermodynamics is essentially the statement of the principle of conservation of energy for thermodynamical systems", indicating that the laws are not identical, but that one is a special case of the other. He proceeds to derive the first law from the principle of conservation of energy over several pages. This also is a de facto acknowledgement that the two laws are not identical as he says. First Fermi heats some water with a flame. Then he raises its temperature by doing work on it with a paddle. Fermi on page 25 defines an adiabatic change as being reversible, and thus his heating of the water by a paddle does not provide an example of an adiabatic change by his definition. He does not in this derivation offer an independent empirical way of measuring heat for this derivation. Instead he tries to reason without allowing the flow of heat into or out of the system. This may seem very clever, but it makes the very meaning of the usual statement of the first law depend on the substantial validity of the second law.

Having stated the first law in a way that he wishes had expunged the notion of heat as presupposed in its own right, but not yet having stated the second law of thermodynamics, Fermi immediately goes ahead to measure the quantity of heat by use of a thermometer and a constant pressure calorimeter, without telling where he got the idea of temperature from.

As PAR notes, Fermi words his first law of thermodynamics avoiding mention of heat and work, instead using the vague word "variation"; he actually admits that this statement is imprecise, when he continues: "in order to give a precise meaning to this statement ...". This is a special point of view and is not suitable to govern the first sentence of a neutral article on the first law of thermodynamics. Fermi notes that "no perfect thermal insulators exist". Therefore he asks the reader to rely on the empirical methods of calorimetry to check for approximate thermal insulation. He has not really expunged heat from his derivation. Though he shows in footnote 3 on page 16 some signs of having followed the Carathéodory point of view, Fermi does not actually state the second law in the Carathéodory form; rather he states it in forms attributed to Clausius and to Kelvin.

Thus Fermi's book does not present a properly logical axiomatic approach, but takes a special point of view and is not in general a reliable source for a neutral article on thermodynamics.Chjoaygame (talk) 08:06, 10 September 2011 (UTC)

Planck (1922/1926) starts his treatise: "Chapter I. Temperature. §1. The conception of 'heat'..."

Fermi (1936) starts his introduction: "Thermodynamics is mainly concerned with the transformation of heat into mechanical work ..."

Guggenheim (1949/1967) starts Chapter 1 of his text: "The most important conception in thermodynamics is temperature."Chjoaygame (talk) 10:23, 11 September 2011 (UTC)

You do have a mastery of the history of the first law, and its many sources, and a very clear heirarchy in your mind about which source trumps which source. There is very little in your response about the meaning of the first law, it is almost entirely concerned with the various sources and their relative position in your heirarchy, and your reasons for placing them there.
Our job as editors is to convey an understanding of the first law, using these sources to support that understanding, not to establish a heirarchy of sources and to quote them. If a monkey types 2+2=4 on a keyboard, then that monkey has typed a true statement. I am more concerned with the truth of that statement than I am with the credentials of that monkey. I will not use that monkey as a source, but I will not discredit that monkey because he does not have a Ph.D. and has not written a well-accepted book or journal article. Your reasons for rejecting Fermi's statement have nothing to do with his understanding of the first law.
The statement above by Count Iblis (one of us mere wikipedia editor monkies) is very informative. You should not ignore it.

In theoretical physics, the first law is taken to be the definition of heat, see e.g. the book by F. Reif. The issue here is that from a theoretical POV (as opposed to a practical POV), the distinction between heat and work is completely arbitrary. If you have some arbitrary system and you don't consider any practical limitations, you can choose your external parameters in any way you like. Work is defined as the minus the change in the internal energy due to the change in external parameters, heat is what is left in order to satisfy conservation of energy.

This very clearly places the first law in the context of the general law of conservation of energy. I do not say this because I have a heirarchy of references to back me up, I say this because the statement says something very clearly to me, and I see no fault with it. Until you can indicate that you have a clear understanding of what he has said and why he is wrong (or right), or a clear statement of why his statement is not logical or meaningful, then you do not understand the first law, no matter how many references and quotes you present, no matter how well you know the history of thermodynamics.
The first law is about the conservation of energy for the thermodynamic case - a case where all of the microscopic parameters of the system are not known. The first law states that there is an internal or thermal energy of the system which depends only upon its state. The sum of change in this energy plus the energy added by work is equal to the energy added by heat. The first law thus defines the concept of heat.
Do not ask me for a reference, do not ask me for my credentials, simply ponder the statement and see if it in accord with your understanding. If it is not, then please state clearly why it is not. Do not quote references, do not give me your credentials, simply engage in a conversation about the meaning of the first law as you understand it.

I have asked for help from the Wikipedia:Wikiproject Physics community on this subject. PAR (talk) 01:29, 12 September 2011 (UTC)

I agree with PAR. Any introductory statement about the first law of thermodynamics must stress energy conservation. Dauto (talk) 02:16, 12 September 2011 (UTC)

Response to edit by Jheald

Dear JHeald, it seems you may have been seeing what was being discussed here but chose not to participate in the discussion, but rather to simply use the facility of overwriting. You seem to judge simply by clarity of expression of your viewpoint rather than by reference to reliable sources. Indeed you have simply deleted the previously standing references to reliable sources. So far, you have not entered into the present discussion on this talk page.Chjoaygame (talk) 05:03, 12 September 2011 (UTC)

Reply to PAR You compare me with a monkey. Your subsequent comparing all Wikipedia editors with monkeys does not excuse that.

You are asking me to abandon the usual Wiki policy of working from reliable sources, and to use my own understanding from my own personal point of view instead. You are apparently relying for your comment on your own understanding, with scant or no regard for reliable sources.

You have recently responded to the request by Jojalozzo for help with the statement that "I have time to do some edits, but not time to do research." I suppose you mean the kind of research that can establish reliable sources for a Wiki article.

Your own understanding seems, correct me if I am mistaken, to include the belief that the first law of thermodynamics defines the concept of heat. Perhaps we can move from here, if you will be so kind, with you checking if that last sentence of mine accurately reflects your viewpoint.

A short time before your present talk comment here, I have put the notion of conservation of energy into the first sentence of the lead, thinking that I was complying with your recent demand that "Any introductory statement about the first law of thermodynamics must stress energy conservation." My effort to do just that has been overwritten by Jheald.

I did not respond to the comment by Count Iblis because it seemed rather broad and did not directly address a neutral viewpoint on thermodynamics, but was focused on the theoretical side. Here is that comment by Count Iblis, copy-and-pasted, for discussion here. I will respond right after it.

"In theoretical physics, the first law is taken to be the definition of heat, see e.g. the book by F. Reif. The issue here is that from a theoretical POV (as opposed to a practical POV), the distinction between heat and work is completely arbitrary. If you have some arbitrary system and you don't consider any practical limitations, you can choose your external parameters in any way you like. Work is defined as the minus the change in the internal energy due to the change in external parameters, heat is what is left in order to satisfy conservation of energy.
"E.g., if you take every degree of freedom inthe system as your external parameters, then the heat is always zero, entropy is always zero and every change in the internal energy is due to work." [end of quote from Count Iblis]

Count Iblis' comment cites the 1965 book by F. Rief, Fundamentals of Statistical and Thermal Physics, McGraw-Hill, New York. That book notes in its preface: "I have abandoned the historical approach in favor of one that emphasizes the essential unity of the subject matter and seeks to develop physical insight by stressing the microscopic content of the theory." If Reif had wanted to write about about thermodynamics as such he would have written differently. Instead he wanted to advance understanding in terms of an essential unity of the subjects of statistical and thermal physics. I would like to quote one reliable source, Callen's second edition (1985): "the amalgamation of thermodynamics and statistical mechanics into an undifferentiated 'thermal physics' tends to eclipse thermodynamics."

Count Iblis proposes, as you do, that in theoretical physics, the first law is taken to be the definition of heat. Count Iblis opposes the theoretical POV to the practical. Count Iblis defines work by calculation from changes in the external parameters and defines heat, by appealing to the law of conservation of energy, as a residual without reference to its traditional definition by calorimetry. This is viewpoint different from that of Callen (1985) who writes: "An essential prerequisite for the measurability of energy is the existence of walls that do not permit transfer of energy in the form of heat." As I read this, it makes the recognition of heat and temperature a necessary presupposition for the proper statement of an empirically testable principle of conservation of energy. This will not worry Count Iblis, I suppose, because he takes a theoretical physical viewpoint as dominant, it appears from his comment.

Count Iblis proposes that "from a theoretical POV (as opposed to a practical POV), the distinction between heat and work is completely arbitrary." This is not a general thermodynamic viewpoint, which refers mainly to macroscopic variables; it is a viewpoint of statistical physics.

Count Iblis goes on to consider the entropy of a system consisting of one particle only. This is not the mainstream of thermodynamics, and not even the mainstream of statistical and thermal physics as seen by his source, Reif's textbook. I will not bore you with reliable sources for the view that thermodynamics is about systems with so many particles that the particle aspect is entirely hidden in the macroscopic variables, but again I would like to refer to Callen, as above: "the amalgamation of thermodynamics and statistical mechanics ..." Perhaps there is a good argument thermodynamics should be eclipsed, but I do not see that as a neutral point of view for an article on the subject. For those interested in the statistical approach, it is represented in the various Wikipedia articles on thermodynamics and in Wikipedia articles on it in its own right.

I therefore propose that Count Iblis is not taking the viewpoint of neutral mainstream thermodynamics, which is appropriate for a Wikipedia article on the first law of thermodynamics. I am not disagreeing with what he says, unless it is taken as a reason to eclipse thermodynamics from an article on thermodynamics.

It seems to me that Reif did the right thing, wanting to talk about statistical physics, not wanting to talk about thermodynamics as such, by entitling his book without mentioning it.

PAR, you write: "Your reasons for rejecting Fermi's statement have nothing to do with his understanding of the first law." My reasons were focused on whether Fermi's statement was a reliable source for a Wikipedia article, not on Fermi's understanding.

Dear PAR, you peremptorily order me: "simply ponder the statement and see if it in accord with your understanding. If it is not, then please state clearly why it is not." Of course, I have pondered on the statement and responded with a move to give your viewpoint more emphasis, a move now overwritten by JHeald. I see editing the Wikipedia as more than a check on my understanding. I see it as using my understanding to find reliable sources and put a neutral point of view on the subject in question, with, if appropriate, concomitant recognition of less neutral points of view. You have taken a condescendingly lecturing tone to me before in the talk page on the zeroth law of thermodynamics: "Once you understand, fully understand, an equivalence relationship," as if I did not understand an equivalence relationship. I do not wish to extend this discussion at present to the substance and style of the article on the zeroth law.Chjoaygame (talk) 05:03, 12 September 2011 (UTC)

Reply to Dauto

Thank you for your expression of opinion. My last edit of the first sentence did comply with your opinion that there should be stress on energy conservation, though it has now been overwritten by another that does so to the exclusion of explicit mention of heat and temperature, the most basic concepts of thermodynamics.Chjoaygame (talk)

General remarks

It seems to me that there is a desire being expressed here to make the Wikipedia a vehicle for a particular pedagogical project, as distinct from being a generally accessible and reliable source of neutral encyclopaedic information.

I am sorry that the strong opinions now being expressed were not forthcoming earlier, when I asked for them. These opinions seem to be simply assertions of opinion, without offered reasons in thermodynamics for them, with little regard for the finding of reliable sources or the maintenance of a neutral viewpoint. It seems to me that the present edit by Jheald seeks to suppress the call for reliable sources.

It seems to me that there are viewpoints being pushed here that downplay the importance of the empirical basis of physics. Aristotle is criticized for lacking an interest in the experimental face of physics, but it seems odd to find the same tendency being pushed today.

I am even driven to wonder whether there is an agenda here to appropriate the dignity of the name thermodynamics for more modern subjects though less widely popular subjects, which in my opinion deserve to be recognized on their own merits with their own names.

It seems to me that some of these opinions want to partly or wholly expunge the distinction between the first law of thermodynamics and the law of conservation of energy, or to expunge emphasis on heat and temperature. I do not see that as appropriate for an article about the first law of thermodynamics.Chjoaygame (talk) 05:03, 12 September 2011 (UTC)

I sincerely apologize for any offense taken by my statements, no offense was intended. I think Jheald's edit is excellent, and I will support it until something better comes along, whether from you or anyone else. It makes no reference to thermodynamic temperature, as it should not, since this is defined in the second law. It refers only to those concepts actually defined by the first law - heat and internal energy. The development of these two concepts in conjunction with the principle of conservation of energy is the body of the first law. PAR (talk) 06:39, 12 September 2011 (UTC)

Thank you PAR. Apology accepted.Chjoaygame (talk) 08:31, 12 September 2011 (UTC)

Editor Chjoaygame, it would be more helpful in the future if you could reply to comments using the ":" symbol. Your participation makes these conversations are difficult to follow. The newer edits by JHeald, et al. are most excellent and do a good job of fixing PAR's earlier criticism that this article did not do a good job of stating precisely what the first law is. I am pleased that this article received the attention of the physics working group. 128.231.77.228 (talk) 17:08, 12 September 2011 (UTC)

first law of thermodynamics from a chemist's viewpoint[edit]

The Wikipedia article on Chemical thermodynamics has as its leading sentence: "Chemical thermodynamics is the study of the interrelation of heat and work with chemical reactions or with physical changes of state within the confines of the laws of thermodynamics."

The Wikipedia article on Thermochemistry has as its leading sentence: "Thermochemistry is the study of the energy and heat associated with chemical reactions and/or physical transformations."

The present Wikipedia article on the First law of thermodynamics does not offer an explicit systematic approach to thermodynamics from the viewpoint of a chemist. Accordingly, into the lead I have put links to the Wikipedia articles on Chemical thermodynamics and on Thermochemistry.Chjoaygame (talk) 21:31, 2 September 2011 (UTC)

Definition of heat by Tro[edit]

For the interest of chemists, it may be convenient, while I still have a copy from the library of the first edition of Tro's Chemistry. A Molecular Approach, to put on record here, without prejudice, how Tro defines heat.

His Glossary entry reads: "heat (q) The flow of energy caused by a temperature difference."

His index entry for "heat (defined)" points to his page 246. On page 246 one finds the start of a section headed "Heat". It begins by telling us that "heat is the exchange of thermal energy between a system and its surroundings caused by a temperature difference." The section goes on to tell us how heat is defined or measured by calorimetry, in terms of heat capacity, specific heat capacity, molar heat capacity, and temperature. After that, starting on page 249, Tro provides a section that tells how to calculate work.Chjoaygame (talk) 01:42, 30 September 2011 (UTC)

Statements of the law of conservation of energy and of the first law of thermodynamics by Tro[edit]

While I still have the book on loan, it may also be useful to record how Tro states the two laws. Tro distinguishes the two laws, but our recent edits have expunged the distinction.

His statement of the law of conservation of energy: "Energy can be neither created nor destroyed."

His statement of the first law of thermodynamics: "The total energy of the universe is constant."

Tro defines energy on page 14: "The scientific definition of energy is the capacity to do work."

In his Section 6.2 on the first law of thermodynamics, on page 245 Tro tells the student: "Identify each of the following energy exchanges as heat or work."

Tro's index lists Carlsbad Caverns National Park, but not Carathéodory.Chjoaygame (talk) 19:07, 30 September 2011 (UTC)

exact quote[edit]

The quote in the article is just as written in the cited source, Truesdell's translation, which is accurate. The original German of Clausius reads:

daß in allen Fällen, wo durch Wärme Arbeit entstehe, eine der erzeugten Arbeit proportionale Wärmemenge verbraucht werde, und daß umgekehrt durch Verbrauch einer ebenso großen Arbeit dieselbe Wärmemenge erzeugt werden könne.

It is true, as editor 117.227.59.204 wishes to make clear, that cyclic processes were intended by Clausius, and this is indicated in the article by the sentence that introduces the quote.Chjoaygame (talk) 12:21, 27 November 2011 (UTC)

Recent vandalism[edit]

I suggest this page be semi-protected until the people changing this article to a lame fight club quote go away... since they clearly do not know when to let it go. — Preceding unsigned comment added by 96.35.171.223 (talk) 19:11, 23 January 2012 (UTC)

edit by Count Iblis: request for reliable source[edit]

To the statement that the first law of thermodynamics was originally induced from empirically observed evidence, Count Iblis has added the following: "...however, it is now taken to be the definition of heat via the law of conservation of energy and the definition of work in terms of changes in the external parameters of a system."

As I read things, it is true that some authors (e.g. Pippard 1957/1966, Reif 1965, Haase 1971) define amount of heat transferred to the system by the formula \delta Q = \mathrm d U + \delta W (using the convention preferred by Count Iblis, in which work done by the system is represented by a positive number).

But these authors, as I read them, do not take this formula as the statement of the first law of thermodynamics. On this reading, the edit by Count Iblis seems to be inaccurate in saying that the first law is now taken to be the definition of heat. Perhaps Count Iblis has reliable sources that support his edit. If so, it would be good if he would say which they are.Chjoaygame (talk) 16:54, 27 August 2012 (UTC)

Sign convention once again - NPOV needed[edit]

This talk page shows that the sign convention for thermodynamic work has been discussed for several years, and we still have a problem. Today Chjoaygame changed the article to the chemists' convention (dU = δQ + δW), and I supported this change by providing a source and changing the equations in another section to agree with this convention. But then Count Iblis changed back to the historical convention (dU = δQ - δW) and changed back all (or most?) of the equations. So perhaps we should resolve the sign question here before changing more equations.

This controversy exists in the real world (i.e. external to Wikipedia) with numerous textbooks on both sides, so I think that Wikipedia has to adopt WP:NPOV and start by mentioning both viewpoints with sources and motivations for each, perhaps in a section explicitly labelled Sign convention for work. At the end of that section, we can mention that the rest of the article will choose one convention for simplicity and recheck that all equations conform to that choice, but that the reader can switch to the other convention by changing the sign of work throughout.

As for sources, we now have the IUPAC document for the chemists' convention and can add Atkins and/or another well-known physical chemistry text. Could someone who is used to the historical convention suggest the best sources for that choice?

I have avoided specifying whether the historical convention should be referred to as from physics or from engineering. My understanding is that it is based on the early history of thermodynamics as a study of heat engines which were built to provide work for human use, so that it was natural to regard work done by the system as positive since it is useful. The chemists' convention on the other hand is based on energy transfers to and from parts of the universe considered as systems which can exist independently of any human use, so that energy transfers to the system as heat and as work are treated as an equal footing. Other comments above (e.g. sec. 11 and sec. 21) also relate the historical sign convention to the thermodynamics of engines.

Other opinions? Dirac66 (talk) 21:32, 27 August 2012 (UTC)

Some references[edit]

Clausius (physics) (German 1854, English 1856) on page 484 writes Q =U +A .W .

Planck (physics) (seventh German 1923, third English 1927 edition) on page 48 writes U2U1 = Q +W .

Tolman (physics) (1938) on page 529 writes ΔE =QW .

Partington (physical chemistry) (1949) on page 150 writes E2E1 = qw .

Fowler & Guggenheim (statistical thermodynamics for physics and chemistry) (1965) on page 57 write q = ΔEw .

Guggenheim (physics and chemistry) (1967) on page 10 writes dU Σ = q +w .

Pippard (physics) (1966) on page 42 writes dU = q +w .

Reif (physics) (1965) on page 122 writes ΔĒ = −W +Q .

Kittel & Kroemer (physics) (second edition 1980) on page 228 writes dU = đWQ .

Adkins (physics) (third edition 1983) on page 32 writes ΔU = Q +W .

Callen (physics) (1985) on page 37 writes dU = đQWMWc .

Bailyn (physics) (1994) on page 79 writes đQ −đW = dU .Chjoaygame (talk) 00:59, 29 August 2012 (UTC)

Ah, thank you. Your library is much more extensive than mine. On placing Q and W (or q and w, or dQ and dW etc.) on the same side of each equation, I find 5 with Q-W (starting with Clausius) and 7 with Q+W (starting with Planck). Close to even, which I think supports my point that we should start by discussing both conventions on an equal footing, before choosing one to present all the equations.
Re Clausius - Did A.W. mean Available Work? Or was it A(Arbeit) in the German and W(Work) in the English? Dirac66 (talk) 01:30, 29 August 2012 (UTC)
The other way round: Clausius wrote: "Nennen wir die äußere Arbeit W, und das Wärmeaequivalent für die Einheit der Arbeit A, so ist der Werth des dritten Thieles A . W, ..."
I just chose enough to give an indication that there is no unanimity, not to provide a statistic. I looked up writings by Kelvin, Maxwell, Tait, Rayleigh, and didn't find them writing either; perhaps I didn't look hard enough. I would find it hard to see a simple way to say why writers choose as they do.
I would consider using the rule of the purple cow here: "Weigh up the alternatives carefully, make a rational decision, and then act in the opposite way." I am inclined to think that we should follow Clausius because he was the first to make the choice. Then we could make a comment about it, perhaps in more detail than the present comment. As it happens, that seems to leave the article largely as it is at present, with perhaps an extended comment. I don't have burning feelings about it.Chjoaygame (talk) 03:08, 29 August 2012 (UTC)
There is no unanimity and both conventions were and are widespread enough so that more explanation of the signs is needed. I will agree to leaving Clausius as the principal convention in the article, but we should point out clearly when the opposite choice is used, as in the quote from Crawford, to make clear that the change of sign is not an error.
I will try to better explain the signs fairly soon. Is Planck's 1923/1927 book just called Physics in English? I thought to cite it since it is the earliest reference you have found which uses Q+W, so it would be good to have the correct title, publisher, etc.
Finally, thanks for the explanation of Clausius' "A.W" I see that his A factor was the mechanical equivalent of heat, later viewed as just a conversion from work units to heat units (J → cal or whatever units he used in 1854). Since all the 20th-century references suppress this factor by measuring work and heat in the same units, it is probably not worth mentioning in the article. Dirac66 (talk) 19:10, 29 August 2012 (UTC)
It would be a mighty labour to try to trace the history of the sign. Not something I want to do.
Planck used both forms in his post-doctoral professorial thesis of 1880. There he denoted the external work done by δW and wrote δQ = δU + δW . But also he referred to the work of elastic force (in effect the work done on the body), which he denoted δΦ, and wrote δW = – δΦ and thus δQ = δU – δΦ. Call it how you please.
In 1883 in Wiedermann's Ann. Phys. Chem., 19, p. 358-378, 1883 Planck was still writing δQ = δU + δW .
Though I don't know if it marked any particular event in the history of the sign convention, perhaps a reference for U2 − U1 = Q +W , that will serve your purpose, is
Planck, M.(1897/1903). Treatise on Thermodynamics, translated by A. Ogg, Longmans, Green & Co., London., p. 43.Chjoaygame (talk) 05:26, 30 August 2012 (UTC)

both sign conventions[edit]

I have now added brief indications of the motivation and origins of the two sign conventions from Clausius and Planck (though I was careful not to say that Planck was the first to use dq + dw since I don't know that). As you said, the changes are relatively minor, but I think they may help some readers who wonder why some books use one convention and some the other. Thanks for the discussion and the references. [Dirac 66, 16 September 2012]

I have taken the liberty of putting in some new headers. I hope you will be happy about that. If you wished to copy your original signature to the newly created orphan-like sections, I would agree with that.Chjoaygame (talk) 23:37, 16 September 2012 (UTC)
Also I have taken the liberty of making some slight changes in your edit, which I hope will meet with your agreement.Chjoaygame (talk) 00:15, 17 September 2012 (UTC)
These changes do make things clearer for the reader so I agree. The only problem I see is that Crawford's statement of the first law is an exception to the claim that the dQ - dW convention is used "generally in this article". So we need to point that out, and I will ask you to decide the best way to do that. Dirac66 (talk) 01:40, 17 September 2012 (UTC)

Historical origins[edit]

Two other points in the article which I think could be improved:

  1. Mayer's 1841 statement is stated to be not a general statement of the first law, but it is not very clear why. Is it just because he specified constant pressure, or was something else missing? [Dirac66, 16 september 2012]
As you observe, it seems Mayer specified constant pressure. It might be argued that the notion of internal energy is essential to the first law, and that Mayer did not discover this notion. It might be argued that Mayer was early in stating the principle of conservation of energy, but that though this is more important and more general, it is not the same thing as the first law of thermodynamics, which is specialized for thermodynamics. Truesdell's sections 7C, 7D, and 7E give a discussion of the relevant work of Mayer. In a discussion of the explanation of heat as motion of microscopic particles and as radiation, S.G. Brush (1976, The Kind of Motion we Call Heat, North Holland Publishing Company, Amsterdam, ISBN 0-7204-0482-7, book 2, section 9.5) mentions Mayer's early statement of the law of conservation of energy. On page 54 of book 1, Brush writes: "The metaphysical arguments with which Mayer supported this principle [of energy conservation] were not much appreciated by physicists of the mid- and late-19th century, ..." Brush on pages 569 and 570 of book 2 attributes the first law of thermodynamics to Clausius and to Rankine in 1850, and to Kelvin in 1851, though Brush does not place much emphasis on the first law of thermodynamics as such.Chjoaygame (talk) 01:20, 17 September 2012 (UTC)
OK, thanks. I see that the answer to my question is quite complicated, so perhaps it is best to leave the mention of Mayer as is. Dirac66 (talk) 01:50, 17 September 2012 (UTC)

Citations with the epithet 'respected' instead of the source's name[edit]

  1. The article lists several respected texts, respected authors, etc.. Sounds a little like a newspaper quoting anonymous sources, although in our case the names are available to the reader with a little more effort. Would you object to writing Reif says, Kittel says, etc.? Dirac66 (talk) 20:56, 16 September 2012 (UTC)
I would favour the reader looking at the footnote rather than the text stating the name. In this case, I see the emphasis here as giving, not the particular views of individual persons, but rather, examples of a range of views.Chjoaygame (talk) 01:31, 17 September 2012 (UTC)

Latent heat capacity?[edit]

In the section Adynamic processes, what does the term latent heat capacity mean, please? I have never seen this term. I have just added links for latent heat which refers to energy absorbed without temperature change, and for heat capacity which refers to the heat energy to effect a unit temperature change. So does latent heat capacity refer to absorption of heat with or without temperature change?? Is it a synonym for specific heat of phase change? Or should it be just heat capacity without the word latent? Dirac66 (talk) 01:25, 26 October 2012 (UTC)

Fair comment. The words latent heat capacity intend to mean absorption of heat by the whole body without temperature change. They do not intend to mean specific heat, and do not intend to mean heat capacity without a specified path.
I see what you mean. You are reading the words 'heat capacity' to refer exclusively to heat transfer that leads specifically to temperature change. I have myself not read it exclusively like that. I would say that the lead of the article Heat capacity is loosely formulated. A heat capacity needs more qualification than the lead of that article provides. A heat capacity is properly stated with a qualification of respect to the path of heat transfer. Is it a path of constant volume, or of constant pressure, or of maintenance of some other specified constraint? The lead of the Heat capacity article avoids this, perhaps for the sake of simplicity. So, in my reading, the weakness is in the failure of the lead of the article on Heat capacity to specify the path and in particular in its unsourced possible implication that the path is not permitted to be a constant temperature path.
A heat capacity, unqualified, usually refers to the amount of heat absorbed by the whole body. A specific heat usually refers to the amount of heat absorbed by a standard mass of the material of the body. Adkins 1975/1983 on page 43 writes of "specific heat capacity", which I would say was a qualified use of the phrase heat capacity; he then remarks that this term is often abbreviated to specific heat. He writes "The various heat capacities are usually represented by the symbol C to which is added a suffix indicating the constraints and a superscript in brackets showing the variable with respect to which the differential is made." He then refers amonst other things to usage of the symbol C for paths of constant temperature.
The word latent says that the heat is to be absorbed along a path without temperature change; there is no such thing as a latent heat with temperature change, I think. On page 85 Adkins writes "Latent heats correspond to a sudden change in the order associated with a first order phase change ...". On page 119 Crawford writes "Then dQT/dp is a new kind of heat capacity, ...[it] represents a sort of latent heat."
In the index of Prigogine and Defay 1954 I find "latent heat of fusion", "latent heat of pressure change", "latent heat of of vaporization", and so forth. In the index of Landsberg 1987 I find "Latent heat of pressure or volume increase". In the index of Crawford 1963 I find "latent heat of expansion", "latent heat of pressure rise", "latent heat of sublimation", and so forth.
In a brief search have not found a use of the exact phrase 'latent heat capacity'. I would think that it would not be an abuse of language to write of latent heat capacity, but I could not insist. I expect you will do what is best.Chjoaygame (talk) 20:02, 26 October 2012 (UTC)

Poor quality of enlarged formulas.[edit]

I'm not sure if anyone else sees this, but it appears that the formulas are images of rather poor quality. It might just be my computer, but I would recommend replacing the images on these formulas. --Kodiak42 (talk) 22:48, 7 November 2012 (UTC)

Semi protection[edit]

This page has been linked to on a facebook page and this seems to be bringing in a lot of vandals. I suggest that this page be semi-protected so this can die down. TornadoLGS (talk) 21:13, 25 November 2012 (UTC)

The fellow who puts in statements of the form "You don't talk about thermodynamics" has been doing it for some time. I don't know how long the page has been linked to on a facebook page.Chjoaygame (talk) 21:36, 25 November 2012 (UTC)
Now it's bringing in copycats though. It seems likely this will be a long-term problem given the Fight Club reference so why not semi-protect it permanently? I really don't understand why flyby IP editors are allowed in the first place. Most of their edits are vandalism, and most of those that aren't are unconstructive or just plain wrong. KarlM (talk) 21:58, 25 November 2012 (UTC)
Yes, it seems protection is needed urgently.Chjoaygame (talk) 22:09, 25 November 2012 (UTC)

Beta decay[edit]

From the section Overview of the weight of evidence for the law: An experimental result that seems to violate the law may be assumed to be inaccurate or wrongly conceived, for example due to failure to consider an important physical factor. It might be interesting here to mention the most notable 20th-century example which was beta-decay, originally supposed to be emission of an electron (only) from a nucleus. [From memory:] experiment in the 1920s showed that the electrons (beta-particles) from a given isotope varied in energy, which was difficult to explain since the energy (mass) difference between parent and daughter nucleus is constant. Apparently around 1930 Bohr actually proposed that in beta-decay the conservation of energy is only obeyed on average over many events. The correct resolution of the problem is that beta-decay involves emission of an electron and a neutrino, as proposed by Pauli in 1930 and in more detail by Fermi in 1933. The neutrino was confirmed experimentally only in the 1950s, but was universally assumed to be correct much earlier essentially because physicists assumed that the first law is correct.

Do others think the example of beta-decay should be mentioned in this article? Dirac66 (talk) 21:44, 7 January 2013 (UTC)

It is an important point that you make. I would say, however, that the point belongs more to an article on the conservation of energy than to one on the first law of thermodynamics. It is true that the first law of thermodynamics is a version of the law of conservation of energy, but it is a specialized version, from the viewpoint of thermodynamics. Beta decay is not very directly about heat and work and the more general concept that was derived from them, entropy; beta decay is really directly about energy as such. Sorry I forgot to sign.Chjoaygame (talk) 08:09, 9 January 2013 (UTC)
Yes, probably the article on conservation of energy would be a better place. I'll think about what to add to the history section there. Dirac66 (talk) 23:46, 8 January 2013 (UTC)
Sounds good to me.Chjoaygame (talk) 08:09, 9 January 2013 (UTC)

Open systems[edit]

Reading Smith, D. A. (1980). "Definition of Heat in Open Systems". Aust. J. Phys 33: 95–105. Retrieved 8 March 2013. .

The example of evaporation in the open systems section states "Consequently, the energy transfer of the process as a whole, though having a component of mechanical work, cannot be uniquely split into heat and work transfers to or from the open system." According to Smith, it can. Specifically, the first law for a reversible, open, simple, one-component system may be stated dU=\delta Q+\delta W+u'\,dM where u' is the energy per unit mass of the added mass. The work is the pressure times the change in volume minus the change in volume due to the evaporation. In other words, \delta W=-P(dV-v\,dM) where v is the specific volume of the added mass, and dM is the added mass. The heat \delta Q is the remainder. PAR (talk) 23:35, 13 March 2013 (UTC)

We are talking fine points here. The term u′ dM is a quantity of internal energy, of a slightly unusual character, apparently specially concocted for the present purpose. It seems hard to say what is the total work and the total heat because of this. The terms δW and δQ are perhaps not the total work and total heat. It think it remains true that "Consequently, the energy transfer of the process as a whole, though having a component of mechanical work, cannot be uniquely split into heat and work transfers to or from the open system." The case of more than one chemical component still I think resists splitting into heat and work. The split is claimed by Smith to need the one-component case. I think Smith is saying that no generalization of theory is needed for the one-component case. For the more-than-one-component case, I think it is still true that a real generalization is needed. That is an argument for considering Münster's more abstract or general statement of the first law for open systems. I am not sure about this.Chjoaygame (talk) 23:56, 13 March 2013 (UTC)
The u′ dM term is the energy of the added mass. Conservation of energy says that the change in energy of the system is equal to the change in energy of the system without the added mass plus the energy of the added mass. Taking \delta Q +\delta W as the change in energy of the system without the added mass (i.e. as for a closed system), the equation makes perfect sense - its conservation of energy. Then saying that the addition of the mass does no work means that the pressure times the volume change due to the added mass does not constitute work. v dM is the volume change due to the added mass for a reversible process. It all fits together. I think to characterize the u′ dM as "concocted" and then use that to dismiss the conclusions drawn is not right. What is needed is an illustration that the line of reasoning leads to an ambiguity or contradiction.
I think it is quite true that for multicomponent system there are indeed ambiguities and the distinction between heat and work is arguable. PAR (talk) 00:45, 14 March 2013 (UTC)
To be fair, I was non-committal, not dismissive. I wrote: "I am not sure about this."
Thinking a bit more about it. I accept, and did not intend to deny, that as a manipulation with mathematical formulas, the Smith story that you have posted makes sense, and is not ambiguous or contradictory. But I am not overjoyed with this story right here in the Wikipedia. I described it as "concocted", not as invalid. If viewed as an introduction to open system thermodynamics, it seems to me a bit artificial and formalistic and ad hoc. Indeed, Smith says: "Thus in homogeneous one-component systems the mass is almost an irrelevant variable; all changes can be described by using the laws of closed-system thermodynamics on thermodynamic densities." This is not exactly a clarion announcement for a statement of open system thermodynamics. The Smith treatment of one-component systems does not offer a very notable new physical insight. It would easily be read as hiding an important physical reality. It avoids or evades a hard-line work-heat distinction by simply ad hoc allowing a third kind of energy transfer, not considered in closed-system thermodynamics, namely transfer of internal energy. As I read Münster, strictly speaking, in general, all open system energy transfer is transfer of internal energy, punto. For open systems in general, including one-component systems, and especially for multi-component systems, the standard and well-established definition of adiabatic work, which is such a prominent and celebrated feature of the Carathéodory story, which we also celebrate, is not applicable, and cannot reasonably be made applicable by a simple word game. When it comes to physics, open systems call for a real generalization beyond the closed-system thermodynamics of the Carathéodory story. The Gibbs presentation of open system thermodynamics is a real generalization. It works mostly by direct postulation of the main facts. It does not try to offer the same depth of sourcing from empirical facts as does the Clausius-Kelvin-Carathéodory story. There are a few references in English to the German text of Falk and Jung 1959, which I have not seen. This is not trumpeted in most textbooks, but is real.Chjoaygame (talk) 05:48, 14 March 2013 (UTC)

the lede needs work[edit]

The lede is quite bloated and unclear. I think the much shorter version here https://en.wikipedia.org/w/index.php?title=First_law_of_thermodynamics&oldid=552178362 is significantly better, but probably something in between would be best. Waleswatcher (talk) 19:20, 10 December 2013 (UTC)

Semi-protected edit request on 25 December 2013[edit]

Section 5 reads: "Evidence for the first law of thermodynamics for closed systems

The first law of thermodynamics for closed systems was originally induced from empirically observed evidence. It is nowadays, however, taken to be the definition of heat via the law of conservation of energy and the definition of work in terms of changes in the external parameters of a system. The original discovery of the law was gradual over a period of perhaps half a century or more, and some early studies were in terms of cyclic processes.[1] The following is an account in terms of changes of state of a closed system through compound processes that are not necessarily cyclic. This account first considers processes for which the first law is easily verified because of their simplicity, namely adiabatic processes (in which there is transfer as heat) and adynamic processes (in which there is no transfer as work)."

HOWEVER

for the last sentence to be consistent with the text, it must read: This account first considers processes for which the first law is easily verified because of their simplicity, namely adiabatic processes (in which there is NO transfer as heat) and adynamic processes (in which there is no transfer as work).

SO

I have added the word "NO" inside the first pair of parentheses about adiabatic processes to read adiabatic processes (in which there is NO transfer as heat)

WHICH

is consistent with the second pair of parentheses about adynamic processes which reads "adynamic processes (in which there is no transfer as work)"

71.65.211.194 (talk) 02:51, 25 December 2013 (UTC)

Oops, thank you for noticing that. I have now made this correction. Dirac66 (talk) 03:26, 25 December 2013 (UTC)

Statistical interpretation of work and heat[edit]

One aspect not yet considered is the statistical or molecular interpretation of work and heat. At a recent seminar at my university, I was reminded that the average energy for a canonical ensemble of weakly interacting particles is <E> = ΣNiεi / ΣNi = Σεi exp(-εi/kT), whose differential is dE = Σ(∂E/∂εi)dεi + Σ(∂E/∂Ni)dNi, and that the first and second terms of the differential represent the statistical expressions for the infinitesimal work and heat respectively.

I believe I knew this years ago, but I have not been able to find a source now. Therefore I am uncertain if I have it exactly right, and also am not prepared to answer questions such as what are the exact conditions of validity necessary for the identification of these terms as work and heat. However I do think that the point would be of interest on Wikipedia, so I am asking here whether anyone can find a reliable source and write it properly for inclusion on Wikipedia, either here in the First Law article, and/or in the separate articles on Work (thermodynamics) and Heat. Dirac66 (talk) 02:44, 21 March 2014 (UTC)

It seems you are suggesting that the article needs some information about statistical thermodynamics or statistical mechanical explanations of thermodynamics. I think the place for full accounts of that is in the relevant specialist articles. A brief summary of that would not be an easy thing to write at the level of generality of the laws of thermodynamics. If your suggestion were to find favour, I would prefer a short section that was more of a pointer to the specialist articles than an attempt in this article to briefly expound their essence. Something like this:
Statistical thermodynamical account of the first law
Statistical thermodynamics, also called statistical mechanics, emerged with the development of atomic and molecular theories in the second half of the 19th century and early 20th century. It provides an explanation of classical thermodynamics, including the first law. It considers the microscopic interactions between individual particles and their collective motions, in terms of classical or of quantum mechanics. Its explanation is in terms of statistics that rest on the fact the system is composed of several species of particles or collective motions, the members of each species respectively being in some sense all alike.
I would not favour an attempt to give statistical mechanical formulas in this article. I think it would give an inadequate account of the statistical mechanical understanding, and it would burden this article.Chjoaygame (talk) 08:09, 21 March 2014 (UTC)
As I read your formulas, their physical reference is to a gas of non-interacting indistinguished particles in contact with a temperature bath. The εi are energy levels available to the particles and the dεi are increments in them. The formula does not state the physical factors that determine the energy levels or how their increments occur. It does not say whether the formalism is classical or quantal. The Ni are occupation numbers and the dNi are increments in them. The formula does not say how physically the increments occur. The increments might be by the transfer of energy as heat from the reservoir or by transfer of energy as isochoric work done by an external device. The formulas' independent variables are state variables, and so cannot be expected to provide a general account of transfer processes, which are the main concern of thermodynamics and are in general not described by state variables. The particles are said to be weakly interacting. This really means that their occupation of energy levels is determined not by their mutual interactions within the system, but by their gain or loss of microscopic energy in heat transfers between the system and the temperature bath. "Weakly interacting" means that the system Hamiltonian does not contain intra-system interaction terms, but still there are effective or virtual interactions of the particles by virtue of their sharing contact with the temperature bath. Thermodynamics is largely concerned with strongly interacting particles.Chjoaygame (talk) 16:34, 21 March 2014 (UTC)
One can try to address the general issue here by considering that, in principle, any energy transfer could be considered to be due to work because ultimately everything consists of particles and you can then frame everything in terms of work performed by the particles on each other. Suppose that you are the physics teacher in high school and a clever 15 year old student asks this question. Then obviously, a detailed explanation in terms of statistical mechanics would be inapropriate. But one can still explain the general idea to the 15 year old e.g. by invoking that in a coarse grained picture you don't see the individual particles anymore, that the energy that goes into the invisible microscopic degrees of freedom is heat. That then implies that the relevant quantities should be defined by averaging. So, I do think it s possible to explain this to lay people. Count Iblis (talk) 15:27, 21 March 2014 (UTC)
With respect, this article is about thermodynamics, which does not recognize the particulate composition of materials. The view that one can frame everything in terms of work performed by particles on each other is foreign to thermodynamics; it belongs perhaps to a version of statistical mechanics. If one frames everything in terms of identifiable interparticle work, one has lost the randomness that is necessary for ideas of entropy and temperature; entropy and temperature are essential for thermodynamics. The energy that goes into the invisible degrees of freedom can come from isochoric work, as for example in the experiments of Joule, as well as by heat transfer. This distinction is essential for thermodynamics.Chjoaygame (talk) 16:42, 21 March 2014 (UTC)
Thank you both for your comments. I will agree with Chjoaygame that a brief qualitative comment on the relation of this article's topic to statistical mechanics is more appropriate than the mathematical formula which I have given above, but I would like to add a brief qualitative summary of the statistical interpretation of work and heat. So I suggest using Chjoaygame's formulation plus two more sentences, as follows:
Statistical thermodynamical account of the first law
Statistical thermodynamics, also called statistical mechanics, emerged with the development of atomic and molecular theories in the second half of the 19th century and early 20th century. It provides an explanation of classical thermodynamics, including the first law. It considers the microscopic interactions between individual particles and their collective motions, in terms of classical or of quantum mechanics. Its explanation is in terms of statistics that rest on the fact the system is composed of several species of particles or collective motions, the members of each species respectively being in some sense all alike.
In quantum statistical thermodynamics, work is identified with changes in the energy of the system due to changes in the particle energy levels, associated with changes in volume or another generalized coordinate of the system. Heat is identified with energy changes due to changes in the number of particles occupying each quantum state.
This expresses the essential idea without going into the detailed formula and its exact meaning. I will answer two of Chjoaygame's points about the formula above: 1) it applies more clearly to the quantum version since it contains a sum rather than an integral, and 2) it applies to pV-work as well as (and perhaps more simply than) isochoric work, since the translational energy levels of the particle in a box vary as 1/L2 and therefore decrease with volume. However it is not necessary to discuss these points here if we exclude the actual formula from the article. Dirac66 (talk) 03:07, 23 March 2014 (UTC)
Thank you for these thoughts. I have reservations about the new proposed sentences.
"In quantum statistical mechanics, work is identified with changes in the energy of the system due to changes in the particle levels, associated with changes in volume or another generalized coordinate of the system. Heat is identified with energy changes due to changes in the number of particles occupying each quantum state."
It may be so that quantum statistical mechanics says that, but it radically differs from what thermodynamics says. The new proposed sentences treat work as identical with a change in a vast list of state variables of the system, profoundly contrary to the thermodynamic principle that work is treated as identical with work done by forces in the surroundings acting on the system, regardless of how it affects the system. The new proposed sentences treat heat as identical with a change in a vast list of state variables of the system, profoundly contrary to the thermodynamic principle that heating is gain of energy by the system due to transfer of energy from the surroundings, by mechanisms other than work or matter transfer, regardless of how it affects the system.
It is a very essential principle of thermodynamics that heat and work are described by process variables, not by state variables of the system. The proposed sentences mean that this thermodynamic principle is treated with ignore in quantum statistical mechanics. Moreover, the new proposed sentences offer no replacement for the thermodynamic concepts of heat and work that they have removed from the picture.
I would say, then, to tell about the radically different use of the term work in quantum statistical mechanics would call for a clearly expressed warning of the difference, more emphatic than just saying in a separate section what quantum statistical mechanics does. This warning would be useful only for someone interested in statistical mechanics. For others it would merely be more or less mystifying. Without an explicit warning, the new proposed sentences would risk being confusing.
I don't have my books with me right now, but I seem to recall that Fermi's little book on thermodynamics makes a related claim, that an adiabatic change is reversible? This means that Fermi has forgotten his thermodynamics and is using ideas from quantum theory, more or less along the lines of the new proposed sentences. In thermodynamics, an adiabatic change is one that is purely mechanically driven, without transfer of heat or matter. In thermodynamics, especially in the Carathéodory view, which seems to have prevailed since about 1950, adiabatic changes are often irreversible. Their irreversibility is one of the cornerstones of Carathéodory's logic. I suppose Fermi didn't worry about that. But that makes him not a reliable source on this question, as far as I am concerned. Another naughty boy in this is the otherwise mostly respectable Pippard who writes in a footnote: "Some writers prefer to use adiabatic in the sense of our adiathermal, and to call our adiabatic change a reversible adiabatic or isentropic change." At least Pippard gives notice that he wants to redefine adiabatic, a word used in thermodynamics since its inception, by Rankine, to mean just the same as adiathermal. Another mistake by Pippard is to copy Planck's axiom from which he derives the second law, and to attribute the words to Kelvin!Chjoaygame (talk) 16:32, 24 March 2014 (UTC)
As for your reason (1), Boltzmann considered finitely spaced energy levels.
As for your reason (2), I would say that, interpreted according to the new proposed sentences, the formulas practically exclude isochoric work.
The new proposed sentences seem to say that statistical mechanics ignores two of the most essential quantities of thermodynamics, heat and work, so lacking in interest in them that it takes over their names and uses them for other, different, concepts. In a sense, then, the new proposed sentences contradict the claim that statistical mechanics explains thermodynamics. I fear that the new proposed sentences are more likely to mislead than to enlighten about the principles of thermodynamics.
The new proposed sentences rely on the concepts of quantum energy levels and their occupation numbers. Would it be fair just to pluck these concepts out of the air, or should they be explained in the article?
It is not so much the use of mathematical formulas that I am concerned about here. It is the qualitative aspects. What physical variables are of interest? What is the physics here?
A quick peek at the Wikipedia article on statistical mechanics yields the following quote: "Given these considerations, the best ensemble to choose for the calculation of the properties of a macroscopic system is usually just the ensemble which allows the result to be derived most easily." Translated into ordinary language that means 'Never mind about the physics. Just produce a short derivation of the desired formula.'
Statistical mechanics as an explanation of thermodynamics is not a very simple thing, I think. I would be keen to avoid putting more than a pointer to it into the article on thermodynamics.Chjoaygame (talk) 10:04, 23 March 2014 (UTC)
I have now found the relevant statistical mechanics article which seems to be Microstate (statistical mechanics), so I have added a link to it with a very brief mention of why it is relevant. I will not attempt to explain further in this macroscopic article. Dirac66 (talk) 16:07, 1 April 2014 (UTC)

History - Clausius equation for original statement[edit]

I want to clarify which equation is being refered to in this section:

Clausius also stated the law in another form, referring to the existence of a function of state of the system, the internal energy, and expressed it in terms of a differential equation for the increments of a thermodynamic process. This equation may described as follows:
In a thermodynamic process involving a closed system, the increment in the internal energy is equal to the difference between the heat accumulated by the system and the work done by it.
Reference Clausius, R. (1850). Ueber die bewegende Kraft der Wärme ..., Annalen der Physik und Chemie (Poggendorff, Leipzig), 155 (3): 368-394, page 384 [3].

Is there a reference for this description being derived from Clausius equation, Clausius himself did not use the terminology "thermodynamic process"? Is it equation (IIa) on page 384? Or is this the description for Clausius equation (57) dU = dQ - dW from his Ninth Memoir? Nerlost (talk) 09:46, 26 March 2014 (UTC)

It is great to see someone actually checking the references.
The description in the article is my personal editorial freehand description of the equation on page 384. No reference. Indeed I did not try to use Clausius' terminology. My aim was to present his idea in present day language. If you feel like improving on it, I will not be offended. I referred to the 1850 paper to in order to defer to Clausius' priority in stating the law. I would still prefer to quote the 1850 paper rather than the 1865 one. I have not tried to present the nearly simultaneous 1850 version by Rankine, but I would not object to seeing that done as well, though I think it perhaps unnecessary.Chjoaygame (talk) 15:06, 26 March 2014 (UTC)

not interior work[edit]

Editor Nerlost, as I read your edit, I think you have confounded Clausius' "interior work" with internal energy. I think that is a mistake of physics. As I understand Clausius, "interior work" is in his terms a thing entirely different from internal energy. "Interior work" as I understand Clausius' terminology is not a function of state. It is a process function. In this context, the pressure-volume integral measures the external work in Clausius' terms, which nowadays is just called the pressure-volume work, another process function. In the present example, Clausius says that the function U can be analyzed as comprising two parts, (1) the sensible heat and (2) the heat necessary for "interior work". The function U is a function of state, namely of the pressure and temperature before and after the process.

Since you are obviously editing in good faith, I have not undone your edit, and I leave it to you to correct it.

True, here Clausius does not actually name the function U, and in particular he does not name it as the internal energy. That is a freehand description of his formula. It uses present day terminology for the easy understanding of the reader, to make it clear that Clausius was early in the use of the notion of internal energy, which is central to the first law. Clausius says that U can be written c dt where c denotes the specific heat of the gas as constant volume and dt denotes the increment of temperature. He adds that it is probable that c is a constant. Joule's second law states that indeed it is a constant, so that the fixed mass of gas has internal energy just simply proportional to temperature. Joule based it on experimental data. Joule's second law describes specifically an ideal gas, which would have been in Clausius' mind. My suggestion for the needed correction is just to omit the words "interior work".

Also I would prefer the previous wording "another" instead of "mathematical". The point is that the idea here is not just mathematical. The internal energy narrowly construed is just a mathematical function, but more broadly construed it is a basic physical notion. It refers to the energy that is internal to the body, a concept more or less in its own right physical. The difference between the two formulations is not merely mathematical, as the word "mathematical" might be read as intending. The difference between the two formulations is that one relates process functions heat and work without mention of the state function U, while the other is focused on the existence of that state function. I think that is more than a mathematical difference. I think it is importantly a physical difference.Chjoaygame (talk) 04:52, 16 April 2014 (UTC)

Absent a response here from User:Nerlost, I am undoing his edit, which I have criticized above.Chjoaygame (talk) 06:23, 19 April 2014 (UTC)

undid good faith IP edit; reason[edit]

I undid this good faith IP edit for the following reason.

It is not merely trivial that the two terms 'law of conservation of energy' and 'first law of thermodynamics' survive. Some writers do indeed identify the two, and treat them as one and the same. The proper distinction is that the law of conservation of energy is more general than the first law of thermodynamics. The first law is stated in many texts in a way that refers to thermodynamic systems, which are members of only a specialized subset of physical systems. The law of conservation of energy refers to physical systems in general.Chjoaygame (talk) 18:15, 11 May 2015 (UTC)