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definition

It has been well settled by consensus on this page that the article should use the Carathéodory approach, as advocated by Born, for its primary definition of heat. Part of the reason for this is that it is admitted that a physical system in the surroundings of a thermodynamic system may be so rapidly changing that it does not have a temperature but still it may engage in transfer of energy as heat with the thermodynamic system.Chjoaygame (talk) 18:09, 8 December 2013 (UTC)

If the article is going to use the term "hotness", it needs to be defined better. Also, "regular" was introduced prior to being defined. Spiel496 (talk) 18:58, 8 December 2013 (UTC)

I think defining "heat" in terms of "hotness" is a bad idea, especially in the lede. I'm changing it back to the slightly older wording, which is not wrong (heat exchange does occur when two bodies are at different temperatures, even if it can also occur in situations where the temperature is not defined). Remember, the lede is a brief summary of the most important points for the lay reader, not a technical treatise that must cover every possible case. Waleswatcher (talk) 09:21, 10 December 2013 (UTC)

We have now an edit to the temperature article that reads "Heat is defined as energy that is spontaneously transferred of energy between two bodies of different temperature, if they are in thermal contact." Perhaps one cannot know why the editor chose to write that, but he would have had aid and comfort if he had glanced rapidly at the new lead of the present article on heat. Its first sentence reads "In physics, transfer of energy as heat between two bodies is a spontaneous process that occurs when the bodies differ in temperature and have a physical connection." If he were an intrepid reader he might have reached the second sentence that reads "Heat is defined as the quantity of energy transferred other than by work or by transfer of matter." He would have had to read further to find out that transfer of energy as heat does not require the two bodies to have temperatures, but that it is from a hotter to a colder body.

Introducing heat in ordinary language in terms of warmth and coldness was good enough for page 1 of Planck's Treatise. So far as I know, an exact equivalent for the ordinary English word hotness (as found in the Oxford English Dictionary) is not used in German, Wärme doing the job. On page 1 of his Treatise, Maxwell wrote "The words hot, warm, cool, cold, are associated in our minds with a series of sensations which we suppose to indicate a corresponding series of states of an object with respect to heat." Maxwell does not actually use the word hotness. According to Adkins "Temperature, as we have defined it, need not bear any simple relation to our intuitive ideas of hotness."<Adkins, C.J. (1968/1983), Equilibrium Thermodynamics, third edition, Cambridge University Press, Cambridge UK, ISBN 0-521-25445-0, p. 20.> Pippard uses the word hotness four times on page 18.<Pippard, A.B. (1957/1966), The Elements of Classical Thermodynamics, reprint with corrections, Cambridge University Press, Cambridge UK.>

In physics, hotness is recognized as a more primitive or general concept than temperature. Bodies that have temperatures are in special states that lie on a special one-dimensional hotness manifold. A numerical scale on that manifold qualifies as a temperature.<Serrin, J. (1986). Chapter 1, 'An Outline of Thermodynamical Structure', pages 3-32, especially page 6, in New Perspectives in Thermodynamics, edited by J. Serrin, Springer, Berlin, ISBN 3-540-15931-2.>

A previous objection to the use of the word hotness in the lead was that it was then not defined in the body of the article. It was consequently defined in the body of the article, but that definition was deleted when the words hotter and colder were used instead of the word hotness, which was objected to.

Hotness is the tendency to transfer energy as heat.<Baierlein, R. (1999), Thermal Physics, Cambridge University Press, Cambridge UK, ISBN 0-521-59082-5, p. 349> Baierlein writes: "All physical systems are capable of heating or cooling others." Even those that do not have temperatures. Thus hotness may be regarded as being defined by its usage in a previous version of the lead: "In physics and chemistry, especially in thermodynamics, transfer of energy as heat between two bodies is a natural spontaneous process that occurs when the bodies differ in hotness and have a suitable physical connection," and in more detail in the deleted section about it.

There has been for some time an extensively discussed consensus in the present article that heat is not defined in terms of temperature. This has been considered a major point of physical principle. The point was perhaps first made in the early days of the twentieth century, for example by Bryan (1907). Encouraged by Born, Carathéodory (1909) wrote an important article which set the stage for heat to be defined without prior definition of temperature. Many texts are careful to recognize this.

It has been proposed that this is too fine a point for the lead of a Wikipedia article, as beyond the lay reader. I think many laymen already have a good idea that heat passes from a body of higher to one of lower temperature. I suppose they would come to the Wikipedia wanting a more. I don't see that the difference between hotness and temperature is too fine a point to interest them, even in the lead.

The present lead does not tell the reader that heat spontaneously passes only from the hotter to the colder body, or from a body with a higher to one with a lower temperature.

I am thinking of making some edits to the lead.Chjoaygame (talk) 09:48, 4 January 2014 (UTC)

Heat: is it energy or transfer?

Can we decide once and for all please, whether heat is "energy" or "transfer"?

After decision is made can we we make all surrounding articles consistent in this respect, please. Even this one is sloppy in this respect.

To Chjoaygame: preempting your suggestion of " you are free to remedy that fault": unfortunately I cannot accept this generous invitation. As I have already explained I am not even an amateur in this area. I merely see logical flaws (I guess because nobody else reads these articles, only writes :-) Staszek Lem (talk) 17:00, 29 August 2013 (UTC)

I do not see how heat can be transfer. Heat flow is transfer.--Ymblanter (talk) 17:45, 29 August 2013 (UTC)

Let's try using the term "payment" as an (imperfect) analogy to "heat", with "money" (or "currency") being the analogy to "energy".

Here are two examples of usage of the term "payment" (and "money"):

(A) "I am waiting for payment.", or

(B) "I have a lot more money than yesterday, because I received a payment of $1000 from Joe"..

I would say payment is both of these:

(1) a type of process or event (whose occurrence "I am waiting for" in example (A) above), and

(2) an amount of money being transferred in that process (this amount is stated in dollar units as $1000 in example (B)).

We probably wouldn't define the term payment by saying "payment is a type of money...", although payment is a type of transfer of some amount of money.

Similarly, we wouldn't (or shouldn't) define the term heat by saying "heat is a type of energy...", although heat is a type of transfer of some amount of energy.

Also, if Joe transferred (gave) $1000 to me (or my bank account), you might ask "what kind of transfer was that", and I might answer "a payment transfer", which is correct, although I might be more likely to say simply "a payment" because you would already understand that a payment is a type of transfer.

In the case of heat, I could also say either "heat transfer" or "heat". Here perhaps I'm more likely to say "heat transfer" to emphasize to the reader that when I say heat I am talking about a type of transfer, especially since the term heat is used colloquially (and even in some treatments of thermodynamics, especially in engineering) in a way that does not necessarily mean there is any transfer involved.

DavRosen (talk) 18:17, 29 August 2013 (UTC)

Sorry to be nasty, but your answers demonstrate several typical severe problems with talk pages in the areas of heat and temperature.

• What I did not:
  • I did not ask for your opinions about heat.
  • I did not ask to teach me heat.
  • I did not ask about difference between "heat transfer" and "heat" (What did I ask, again?).
  • I do not need analogies, because English language is way more confusing than average English speakers suspect (in your case, since you are not an economist (I suspect), you are rather confused or sloppy about precise meanings of the terms "money" and "payment". (ask me in my talk page for explanations))
  • tldr

• What I wanted:
  • What I asked is how to fix a problem I see with the article (inconsistency).
  • In order to do this, I need references, not opinions or explanations.
  • I would accept that :
    • some texts define heat as "energy"
    • some texts define heat as "energy transfer"
    • some texts carelessly mix the two above
    • some texts mix the two first and say in is OK
    • some texts say it is not OK mix to the two first
  • What I need is clear description of the possible controversy or contadiction to be added to the article, since it is obviously a common problem, to be addressed (based on solid references (sorry to be repetitive, but I did not ask "what do you think about heat", did I?)
  • What I need is a clear consensus, sealed and stamped, in order to fix many articles without diving into the same controversy again and again.

So far, I see two opposing wikipedians' opinions. Care to prove them with references? Staszek Lem (talk) 19:04, 29 August 2013 (UTC)

• Heat is energy being transferred from one object to another because of a temperature difference alone..unsigned post at 19:35, 29 August 2013 by Ymblanter.

• Here are two quotes from a widely accepted textbook: "An energy transfer via the hidden atomic modes is called heat. Of course this descriptive characterization of heat is not a sufficient basis for the formal development of thermodynamics, and we shall soon formulate an appropriate operational definition."[page 8] "The heat flux to a system in any process (at constant mole numbers) is simply the difference in internal energy between the final and initial states, diminished by the work done in that process." [pages 18–19]

Here is another definition from a well respected textbook: "Instead we may write the equation ΔU = W + Q,     (2·9) and thus define the quantity Q which is a measure of the extent to which the conditions are not adiathermal. The quantity Q so defined is called heat, ..."[page 16]

As I understand your post, Staszek Lem, you are asking can we decide once and for all, whether heat is "energy" or "transfer". I would say that your question is wrongly posed and, taken literally, has no useful answer. Your question more or less presuppposes that ordinary language has a property called compositionality; no, that presupposition is mistaken. Ordinary language is not compositional, that is to say it does not work by giving each word a fixed meaning, insensitive to context; instead it expresses ideas by sentences, which are combinations of words, constructed not according to strict compositional rules, but rather with structural character that is context-sensitive. So in physics and chemistry, heat is neither energy alone, nor transfer alone; it is constituted of a combination of a particular character. Reminiscent of Aristotle's ὕλη and μορφή which constitute οὐσία.

As for your desire for "solid references", it is not easy to satisfy, and it may be unfeasible to satisfy it. Individual style and usage and manner of presentation vary widely in reliable sources. This is mostly not because of significant differences of opinion, but is mostly because of the variability of habits of expression. The idea in textbooks is often presented pedagogically, progressively developing it, even in sections pages apart, often without a one-sentence definition such as is often preferred at the start of a Wikipedia article. I have above cited two texts that may perhaps to some degree come near what you are asking for, but I had to look at several well respected and reliable texts before I found them. It is always the Wikipedia editors' job to say accurately what is in the reliable sources, but not usually to quote them verbatim.

As for your perception that there are "two opposing wikipedians' opinions". It is true that there is a consensus understanding that in physics and chemistry, heat is energy in transfer, and that some Wikepedia editors oppose this for various respective reasons. At present I don't see a need to justify the consensus, because it has been debated at length and settled here already.Chjoaygame (talk) 22:15, 29 August 2013 (UTC)

(re: linguistics) Thank you for teaching me linguistics. I have always thought that exact sciences keep their language ..er.. exact. Here we are not talking a about "ordinary language"; we are talking about the fundamental term in physics. I admit it was partly my fault to receive this particular piece of retort: I was lazy and should have asked "transfer of energy" vs "energy in transfer". Still, whatever compositionality or not, there is a fundamental difference between the terms "transfer" (process) and "energy" (physical quantity) regardless their compositionalitability. And IMHO the "individual style and usage and manner" which confuses them is called "sloppiness" in my school of thought. Staszek Lem (talk) 01:27, 30 August 2013 (UTC)

(re:refs) Who told you that wikipedia insists on one-sentence definition"? Why prevents us to do it "pedagogically, gradually, progressively", i.e., it a readable way? And one of the goals of wikipedia and part of wikipedians' work is to sift through sources and make sense. Staszek Lem (talk) 01:27, 30 August 2013 (UTC)

(re:my perception): sorry, agreed. You may see a consensus, while I see a mess. May be it is settled, but not reflected in the articles. Staszek Lem (talk) 01:27, 30 August 2013 (UTC)

Stazek Lem: Your question was "Can we decide once and for all please, whether heat is "energy" or "transfer"?" The answer is yes. Let's decide "transfer".

Although DavRosen did not answer your question, his analogy is more than an opinion, it is a good way of understanding what is meant by "Let's decide transfer"

As far as a "clear consensus", I think you have it. Let's decide "transfer". Chjoaygame's references are "solid". Other "solid" references may disagree, but we should adopt a consistent definition throughout Wikipedia, and, as you say, provide a description of the controversy on the heat page. "transfer" is the consensus of all responsible editors that I have seen, and I agree with it. The articles do not yet reflect this consensus: It is a work in progress. As Chjoaygame says, "you are free to remedy that fault" or not, as you see fit. PAR (talk) 07:56, 30 August 2013 (UTC)

I do not see any consensus here. My reference (which is btw a standard modern undergraduate text) clearly says "energy", not "transfer".--Ymblanter (talk) 08:01, 30 August 2013 (UTC)

Staszek Lem is asking a very exacting question. He is now telling us that he has "always thought that exact sciences keep their language ..er.. exact". I think the present spread of reliable sources shows that his thought there is mistaken: therefore I will re-word the first sentence of this response of mine: Staszek Lem is asking a pertinaciously demanding question. As I read him, he is still, in effect, insisting that heat is just one of either transfer or energy. His new wording is 'transfer of energy' versus 'energy in transfer'. The difference is that the phrase 'transfer of energy' has transfer as the main word with energy as a prepositional attachment, while 'energy in transfer' has energy as the main word with transfer as a prepositional attachment. The problem is partly due to the elliptic nature of the term heat in physics and chemistry. The fully worded non-elliptic version is 'quantity of energy transferred as heat'. (I have been driven by various pressures in many places to use this non-elliptic version.) The lead has the oft-used ellipsis 'heat' for this six-word phrase. I can imagine the unhappy possibility that we might be driven into putting the non-elliptic version in the first sentence of the lead. Personally I think it would be not good to do this. I hesitate to say exactly why.

In deciding for "transfer", PAR is I think emphasizing that quantity of energy transferred as heat is essentially and necessarily a process quantity, not a state quantity. In going for "transfer", I don't think he means that heat is not a quantity of energy transferred in a particular mode or kind of process. Of course I think he is right that we are talking about a process quantity, not a state quantity.

Ymblanter has perhaps raised two things. One is about the grammar: he persists in wishing to make heat just exclusively one of energy or transfer. I think that wish is misguided, for reasons I have stated just above. The other is where he cites an undergraduate text that defines heat for the special case in which both system and surroundings are described as thermodynamic systems which have their respective temperatures. I think it is agreed by editors here that the more general case, carefully delineated in the article, is the preferred definition: it is not generally to be required that the surroundings have a temperature.

Staszek Lem makes more points. He accuses me of saying that Wikipedia insists on a one-sentence definition. I said "often preferred", not 'insisted upon'. He seems to want a gradual pedagogical presentation in the lead. The body of the article has a fair amount of more or less gradual pedagogical presentation. I don't think it is appropriate in the lead. The history of this article is evidence for that. The lead is a summary, not a pedagogical presentation.Chjoaygame (talk) 09:05, 30 August 2013 (UTC)

I am afraid what you write clearly shows serious lack of understanding of the subject. Very typical for Wikipedia. I am afraid I would rather unwatch this page. Perhaps I am, being a full professor of physics in one of the top universities in the world, and having taught the subject for several years, just not qualified enough to carry out this discussion.--Ymblanter (talk) 09:35, 30 August 2013 (UTC)

The rule here is that you present reasons, not appealing to your own authority. Appeal to your own authority is sometimes seen as argumentum ad verecundiam, and sometimes as argumentum ad hominem. I would like to know where you think there is serious lack of understanding. I am guessing that it may be the idea that the surroundings are not required to be describable as a thermodynamic system with its own temperature, because it is too turbulent or otherwise erratic? This idea has been largely, as I understand it, championed by Editor Count Iblis, and his view has prevailed. If you have something to contribute about it, I would be interested in your view, even if you were not "a full professor in one the top universities of the world, having taught the subject for several years, just not qualified enough to carry out this discussion". Perhaps that guess of mine is way off the mark, and you will tell us what it is that makes you see serious lack of understanding?Chjoaygame (talk) 10:24, 30 August 2013 (UTC)

Heat is energy because Joules are Joules. Since physics instruction often follows historical development many treatments start with mechanical energy, and then transition to heat -- which the ancients thought was a fluid flowing from one body to another. That, and the lack of any means of direct measurement of heat energy in an existing object -- tends to produces as many or more references for the "heat as transfer" meme. NE Ent 12:11, 19 October 2013 (UTC)

Aristotle offered a scheme for scientific explanation. There are four kinds of answer to a why question: material, formal, initiative, final.

Why is this heat? Because materially it is energy. Because formally it is in a particular mode of transfer. Because initiatively it is moved by unmasking of absence of uniform temperature. Because finally it will be completed when uniformity of temperature has been reached.Chjoaygame (talk) 06:18, 20 October 2013 (UTC)

Staszek Lem said: "Can we decide once and for all please, whether heat is 'energy' or 'transfer'? You can think of it as the change (or ∆) of the thermal energy.
Ymblanter said: "I do not see how heat can be transfer. Heat flow is transfer." Heat is the thing being transferred. Heat is the quantity of thermal energy responsible for the change of thermal energy of an object. You can think of "heat flow" as the transfer of the transferred entity "heat". So in the context of classical thermodynamics the term "heat flow" is a redundant way of saying "heat".siNkarma86—Expert Sectioneer of Wikipedia
^{86 = 19+9+14 + karma = 19+9+14 + talk} 18:12, 8 December 2013 (UTC)

This conversation will continue to the end of time until Wiki correctly describes the classical view of heat and then clearly describes why modern text books refuse to recognise correctly the classical view of heat! — Preceding unsigned comment added by 88.112.187.21 (talk) 09:32, 20 January 2014 (UTC)

spontaneous

The useage of spontaneous in spontaneous transfer is wrong. Spontaneous means without regard to external factors. Heating is only possible if there is an external temperature difference. In physics and chemistry spontaneous heat only referrs to exothermic processes where heat erupts from the object as a force that causes additional heating regardless of the temperature of the surroundings. When hot gases or hot objects heat other objects this is not what we mean by spontaneous heating. Ask yourself what is the difference between heat transfer and spontaneous heat transfer. Heat will be transferred automatically by a temperature difference but it will not be transferred spontaneously which happens without regard to the external situation. Wiki on heat is very very muddled up. It distorts the classical meaning of heat due to the modern useage of heat since about 1910/1920 as *only* heat flow where it is now realised heat is not always the kinetic energy of matter. Kelvin and co understood heat as energy in motion or kinetic heat. Anybody who has read these classical texts will know this is true. The current modern view seems mainly preferred by Americans but even that cannot be said of all Americans. Wiki refuses to bring these confusions into the light of day because the editors insist that heat in matter is the much much earlier idea of Caloric. Obviously the dominating wiki editors never had a classical education in heat! I am 58. I suspect these people with so much energy to create meanings that are muddled are much younger than me. — Preceding unsigned comment added by 88.112.187.21 (talk) 08:44, 19 January 2014 (UTC)

It is always a pleasure to be corrected by someone who knows better, especially when they express themselves in a charming way. The use of the word spontaneous might be criticized and I have removed the word.

As for your views on the definition of heat, I think you may see if you look at the history of the article that things are not quite as you propose in your above comment. The present definition of heat transfer originated in about 1908, for reasons other than the ones you suggest. It is now standard in well sourced textbooks, which are the proper sources for a Wikipedia article. The reasons have in the past been discussed in the article, but were removed because helpful editors thought they were too chatty. Perhaps they need to be put back.Chjoaygame (talk) 16:36, 19 January 2014 (UTC)Chjoaygame (talk) 16:51, 19 January 2014 (UTC)

I have now restored the sections that explained the reasons for the currently well sourced definition of heat.Chjoaygame (talk) 17:12, 19 January 2014 (UTC)

The word 'spontaneous' still appears in the highlighted lead. There were two occurances. One has been removed.

On the subject of the modern useage of heat most people including science graduates like myself had no idea the meaning was changed last century. I did my best to research why it was changed because i found it was impossible to edit wiki to properly describe the classical view of heat and neither was it possible to discuss the view on physics forum without being banned for talking about voodoo physics. Obviously there is a very major confusion in most people minds between the idea of a hot sun and the idea the sun has no heat at all.

As for me being charming i do my best. I have already wasted endless hours of my life attempted to get wiki to be something suitable to educate people and my patience was exhausted years ago. It is what is. — Preceding unsigned comment added by 88.112.187.21 (talk) 08:07, 20 January 2014 (UTC)

By the way for the record when i attempted to show a paragraph on latent heat had been confusingly rewritten by perhaps a well meaning editor, you reverted my change and told me it was fine as it was. I then had to point out to you that if you wanted the other editors change you needed to rewrite the paragraph for it to make sense. Somewhat amazingly my change has now managed to last for about 3 months without being changed back to the confusing version. And now with your change to remove 'spontaneous' it is obvious you dont take much care to produce changes and volume of changes where you are dominating is your fixation.

The way heat is described on Wiki is totally weird and yet it is taken as the gospel truth to the point that people like me are regarded as ignorant fools who cant tell the difference between caloric and the description of heat given by Kelvin! Then you want people to be charming to you! — Preceding unsigned comment added by 88.112.187.21 (talk) 08:16, 20 January 2014 (UTC)

It seems you are Damorbel without a signature. I think you are banned and should not be writing here. No further response from me.Chjoaygame (talk) 10:16, 20 January 2014 (UTC)

I am not damorbel. My comments here are relevant to heat. . Wiki heat is simply weird in the way it denies a correct view of the classical view of heat. — Preceding unsigned comment added by 88.112.187.21 (talk) 14:40, 20 January 2014 (UTC)

If you are not Damorbel, and if you are not banned, then I can continue. Your current habit of unsigned posts is troublesome. Please give some information about who you are so that it is clear that you are not banned.

If you are not banned, please give the link to the edit to which you are referring when you write above "By the way for the record when i attempted to show a paragraph on latent heat had been confusingly rewritten by perhaps a well meaning editor, you reverted my change and told me it was fine as it was. I then had to point out to you that if you wanted the other editors change you needed to rewrite the paragraph for it to make sense. Somewhat amazingly my change has now managed to last for about 3 months without being changed back to the confusing version."

I made mistake to remove the word spontaneous. It is rightly used. You are mistaken in saying it was wrong. The transfer occurs between two systems, and occurs spontaneously in the sense that it depends on nothing external to those two systems. You were led into your mistake because you were thinking of heat as belonging to just one system, with the companion system considered external to it. No, heat belongs jointly to the two systems, one the donor, the other the acceptor, in the transfer.Chjoaygame (talk) 20:57, 20 January 2014 (UTC)

new edit

Thank you, Editor guyvan52 for your care in these matters. With all good will, I am not happy with your new edit, but I don't want to undo it. I think it would be better if you chose to do that yourself.

My reasons are several. (1) in physics, nowadays phase changes and ohmic heating are not called heat transfer. (2) strictly speaking even in the days of Maxwell, convection unqualified is not a pure heat transfer. (3) while ordinary language allows your listed processes to be called heat, as you rightly say, I think it unwise to put this as the third sentence of the lead of this article, because it would too easily justify claims that "Wikipedia says it's ok". (4) I think it too valuable space on heat to put an account of work in the first paragraph of the lead on heat. (5) the second paragraph lists again the properly defined physical modes of heat transfer, making one or other redundant in the lead.Chjoaygame (talk) 06:44, 22 March 2014 (UTC)

I made that edit quickly because I wanted it out of Temperature#Zeroth_law_of_thermodynamics. I concede on points (1) and (2) but not entirely on (3) and (4): Sometimes Wikipedia needs redundancy. A week ago I asked a tenured Phd professor for a concise definition of enthalpy. In the course of our discussion I discovered that his definition of "heat" was dead wrong. I don't think he is incompetent, but rather that he (like me) thinks mathematically. We can solve problems and model systems without bothering with definitions. In real life (but not on Wikipedia) words mean what we want them to mean. I will severely edit the passage by replacing words with links.--guyvan52 (talk) 12:57, 22 March 2014 (UTC)

I am unhappy with your new edit. It is not our job to correct tenured professors. They should be self-correcting, and we don't need to worry about them. It is our job to be reliable. I don't like your edit because it is pedagogical for the benefit of tenured professors and other beginners, and over-chatty for a Wikipedia lead. I am not re-editing it right now, but I reserve the usual right to do so in future. Also I particularly don't like referring to the Wikipedia article on heat transfer. I have a policy of letting the experts there do their thing without fiddling from me. But here I like to try to get the physics right, using reliable sources. Physics is about physics, with mathematics as a handmaiden.Chjoaygame (talk) 14:07, 22 March 2014 (UTC)

I'm sorry, but your comments make no sense to me. Perhaps I am misunderstanding your words.

1. Your reference to an edit for the "pedagogical benefit of tenured professors and other beginners" seems weird to me. People need to be told that heat is not the same as energy, and the lead is a good place to say it. Wikipedia is all about educating "beginners". Many (if not most) college students come into an introductory physics course thinking that "heat" is synonymous with either temperature or internal energy. Such misconceptions are difficult to overcome.
2. As for your not liking a link to heat transfer, Wikipedia is full of unnecessary links (e.g., 2014). The link to heat transfer was not a reference, but a guide to another article that a reader might want to look at. If a link between Heat and heat transfer is inappropriate, then what is an appropriate link?--guyvan52 (talk) 16:34, 22 March 2014 (UTC)

The reason I don't like to link to the article on heat transfer is that (so far as I recall - perhaps it is changing) it doesn't follow the strict ideas of physics. It is, I seem to recall, written from other perspectives. For physics, heat is a kind of transfer, and a further article on transfer transfer is not needed.Chjoaygame (talk) 02:09, 23 March 2014 (UTC)

Perhaps I should have mentioned that the tenured professor who did not know the definition of heat was in the physical sciences. That is how deep the misconception can go.--guyvan52 (talk) 16:36, 22 March 2014 (UTC) (Perhaps I should add, that's how easy tenure can be to achieve...)

Having said all that, I have to admit that you were right about my edits to the lead paragraph. The lead now stands almost as I found it, with just two (2) changes: (1) Links found vital to the novice's understanding of heat are now located in the first three sentences. These include heat transfer and thermal contact. And (2) since introductory textbooks treat heat and work almost simultaneously, I added one sentence with links to work, state variable, and internal energy (the latter link had been absent from the article). While this (new) second sentence does go a bit off track, students attempting to understand thermodynamics for the first time will benefit. You are a good person to work with. --guyvan52 (talk) 00:20, 23 March 2014 (UTC)

Planck

It is daft to be talking about planck in this article if his definitions of heat are not allowed to see the light of day. All of the classical writers regarded heat as a living force contained within matter. Plancks book on heat had 22 revisions and was published until 1964.

It is a travesty the way the classical view of heat has been erased from text books and wiki and is not allowed to provide a clear explanation why this has happened.

Why?? It is unbelievably weird. — Preceding unsigned comment added by 88.112.187.21 (talk) 09:27, 20 January 2014 (UTC)

This comment is I think from a banned editor and should not be responded to.Chjoaygame (talk) 10:18, 20 January 2014 (UTC)

From the just foregoing, it seems that I was mistaken to think that this was from a banned editor.Chjoaygame (talk) 18:59, 1 April 2014 (UTC)

a mathematical definition can be formulated

In deference to the editor who wrote it, I have not tried to edit the sentence "A mathematical definition can be formulated in terms of the statistical distribution of an ensemble of microstates." But I think there is potential for misleading here.

If a change in the shape of a system is enforced slowly, and if it is very small, then it may change the energy levels of the system in a more or less continuous way, without creating new modes of oscillation. This is the statistical mechanical idea of an "adiabatic change". It is convenient for statistical mechanical calculations, but it should not be confused with an adiabatic change in general thermodynamics. An adiabatic change in general thermodynamics can include a gross change in the shape of the system that will be manifest in creation of new modes of oscillation and new energy levels. With a new set of energy levels, the meaning of 'change of occupation number' is blurred. What has primarily changed is the set of energy levels. Some jumps of occupation seem necessarily part of such a change.

The article on Microstate (statistical mechanics) is rightly careful about this. It writes "Work is the energy transfer associated with an ordered, macroscopic action on the system. If this action acts very slowly then the Adiabatic theorem implies that this will not cause a jump in the energy level of the system." But it does not go on to discuss an ordered macroscopic action on the system which does not occur very slowly. It does not mention the possibility of a thermodynamically defined adiabatic process which is macroscopically large and changes the shape of the system so as to create new modes of oscillation and new energy levels. In this sense, it is well called a mathematical definition, though not much good as a physical definition. It is convenient for mathematical calculations, but it does not give much recognition to the physical fact that natural processes are always irreversible. The statistical mechanical description of general thermodynamic processes is a work in progress, not an established part of physics. I would draw attention to Zurek's view, that for quantum statistical mechanics, physically, the approach to thermodynamic equilibrium requires input of noise from an external source, which means the possibility of transfer of energy as heat between the system and the surroundings.Chjoaygame (talk) 18:56, 1 April 2014 (UTC)

My reason for including that sentence was to provide and explain a link to the article Microstate (statistical mechanics) which contains the equation for the microscopic definition. I do not insist on the exact wording, and would be inclined to accept a revision provided the link is maintained.

Also I notice that you corrected my jumps in energy levels to jumps in occupation numbers. You are right about this, of course, but I checked to see why I had made such a silly mistake in a sentence which I copied from Microstate (statistical mechanics), and found that the sentence is in the other article as well. And has been since 2005 with minor revision in 2008! Shall we just copy your corrected and expanded version from Heat back to Microstate (statistical mechanics)? Dirac66 (talk) 19:24, 1 April 2014 (UTC)

Since I do not watch the statistical mechanics articles, best I leave it to your judgement.Chjoaygame (talk) 19:48, 1 April 2014 (UTC)

OK, I have basically copied the first of your two sentences, slightly rearranged to fit the context. Dirac66 (talk) 00:49, 2 April 2014 (UTC)

emphasis in the lead

Two recent additions to the lead have drawn attention to some points about heat transfer. The locations of the additions, in the first and second sentences, give great emphasis to the two points. The points are important, but I think their emphasis is too much. The matter of state variable versus process variable is specialized for thermodynamics, and one might even say that it is a bit sophisticated. The adversion to the term dissipation is also specialized. Moreover, it introduces into the sentence an idea that is valuable but not quite to the point of the sentence; one might say it overloads the sentence. It breaks the loose rule of one idea per sentence, for ready reading. I am favour of moving the points to separate sentences of their own.Chjoaygame (talk) 09:50, 2 April 2014 (UTC)

Both the links to "dissipation" and "state variable" are to weak articles. Perhaps we should keep the link to "state variable" and let me attempt to make a contribution at or near the lead of state variable. The article on "state variable" makes no mention of "process variable", and for that reason the article doesn't really say much. What is amazing about the state variable is that there exists variables which are NOT state variables.--guyvan52 (talk) 15:13, 2 April 2014 (UTC)

A good way to improve the "state variable" article is to include counter examples that are not state variables. Heat and work make for two. A third of what you call "process variable" not affiliated with thermodynamics would really help the "state variable" article. Can anybody think of any? (I will post this on the state variable talk page, but its relevant here because a better "state variable" article would greatly help out the "heat" article. --guyvan52 (talk) 15:22, 2 April 2014 (UTC)

User:Chjoaygame, I am sympathetic to your wanting to keep the heavily loaded WP on Heat uncluttered. I just found two examples (Berry and Econophysics ) of non-state variables (the phrase process variable has another meaning in WP). Both examples involve inexact differentials. Econophysics might be a forced attempt by a physicist to publish a paper in economics, but Berry's phase of quantum mechanics seems legit (though beyond most reader's comprehension). Fortunately, quantum phase is a good and simple example of a non-state variable, since it is essentially chosen by the one who writes the wavefunction. All you need to do in your prose in Heat is make a link to state variable in the first paragraph; there is no need to force a link to work b/c that will appear in the state variable article. I will add a section to state variable soon with a title that goes something like 'Variables that are not state variables'

• "Perhaps we should keep the link to "state variable"". I did not mean to remove the link. I meant to put it in a sentence further down in the lead.Chjoaygame (talk) 19:37, 2 April 2014 (UTC)

"What is amazing about the state variable is that there exists variables which are NOT state variables." What is a state variable is determined by how you set up your description of the phenomena. In classical thermodynamics, flow rate, pressure gradient, and time rate of entropy production are not state variables, and they are not considered in that subject. In local thermodynamic equilibrium non-equilibrium thermodynamics, flow rate is often a state variable, while time rate of entropy production is a variable of interest but usually I think is not considered to be a state variable, depending on how the scheme is set up.Chjoaygame (talk) 19:37, 2 April 2014 (UTC)

"to keep the heavily loaded WP on Heat uncluttered". I did not talk of clutter. I was just talking about emphasis.Chjoaygame (talk) 19:37, 2 April 2014 (UTC)

"A third of what you call "process variable" not affiliated with thermodynamics would really help the "state variable" article." I disagree. We are concerned with variables for thermodynamics that are or are not state variables. Talk of non-thermodynamic objects would distract without benefit.Chjoaygame (talk) 19:37, 2 April 2014 (UTC)

"a better "state variable" article would greatly help out the "heat" article". I am not complaining about the article on the State function. According to Münster (p. 6) a state function is a function whose differential is a complete differential of the variables of state.Chjoaygame (talk) 19:37, 2 April 2014 (UTC)

"quantum phase is a good and simple example of a non-state variable". I don't think it would help here. I think it would be an unhelpful distraction.Chjoaygame (talk) 19:37, 2 April 2014 (UTC)

• Process variable?? I have never heard the term. In my physical chemistry textbooks the opposite of a state function (or variable) is a path function or path-dependent function. Leave processes for the engineers. Dirac66 (talk) 20:08, 2 April 2014 (UTC)

Process variable -> the term here is Process function Prokaryotes (talk) 21:23, 2 April 2014 (UTC)

Yes, I just realized that WP has four articles...process variable...process function...state variable...state function. None of them make ideal links for the novice who needs to know that the question "How much heat is in that system?" is meaningless. The best link seems to be to process function. Perhaps we should call it one thing and link to the other, e.g., Heat is not a [[state function|state ???]], but a [[path function|process function]]...--guyvan52 (talk) 21:55, 2 April 2014 (UTC)

And now that I understand that the best link is to state function the need to bring up weird non-state variables like Berry phase or econophysics has evaporated. The state variable article is a bit scattered, and including nonthermodynamic process functions would do no harm, but the proper link (i.e. state function) is and should be focused on thermodynamics. Consider my most recent edit a "quick fix"; I think the paragraph can be strengthened as per Chjoaygame's comment.--guyvan52 (talk) 22:17, 2 April 2014 (UTC)

You wrote: "Heat refers to a transfer of energy, not to an internal thermodynamic equilibrium state of the system. Heating is a dissipative process." I find these words confusing for a two reasons:

1. On the first reading, I thought the "to" in "not to an internal..." referred to the verb "transfer", as in the energy is not transfered to a (...) state, but to something else. On the second reading did I realize that the word "to" referred the verb "refers", as in Heat does not refer to a state. Your words seem to be informing the reader that Heat is not something that few people would mistake it for being.
2. I believe that you are trying to say that heat is not a state function. But you have no link to the concept of a state function (or state variable). I always called them "state variables", but the Wikipedia article state function does explain the concept, and therefore we need a link to it.--guyvan52 (talk) 02:35, 3 April 2014 (UTC)

We need a link to state function to show what heat is not, and to process function to show what heat is. However the article process function should also be renamed path function, which would be less subject to confusion with the engineer's process variable. Dirac66 (talk) 02:43, 3 April 2014 (UTC)

Yes, Dirac66 and I are in basic agreement, except that the double link is optional: If one of those links (e.g. to what heat is) contains a clear and immediate link to the other (e.g. to what heat is not), then we can make only one link and let the interested reader find the other. But I do think Chjoaygame had the right idea in attempting to develop one idea at a time with this lead. --guyvan52 (talk) 02:51, 3 April 2014 (UTC)

The reason I did not make the links discussed just above is that the article is about heat, not about terminology. The terminology is the subject of much debate, and of a "weak article", as noted in the foregoing. The physics is that heat is about a kind of transfer, not about a state of internal thermodynamic equilibrium of a system. A time rate of transfer, including rate of heating, can be a state variable in non-equilibrium thermodynamics, depending on how the problem is set up.Chjoaygame (talk) 12:16, 3 April 2014 (UTC)

"Heating is a dissipative process, not a property of a state of internal thermodynamic equilibrium of a system". I like the intent but not the wording: "of" is repeated three times. Will attempt to make it smoother.--guyvan52 (talk) 15:18, 3 April 2014 (UTC) ... Also, the phrase following the comma (...a dissipative process, not a property...) might mislead the reader into thinking a that Heating is either a dissipative process OR a state function (in other words that one somehow implies the other) Work for example, can be not dissipative and not a state function. But you are correct in insisting that this preliminary description of heat include non-equilibrium situations.--guyvan52 (talk) 15:31, 3 April 2014 (UTC)

Another option is to introduce the link to state function in the last sentence of the lead, where it is pointed out that Heat plays an essential role in thermodynamics. We have a curious situation where most of the basic education of the physicist involves thermodynamic equilibrium, while most (if not all) systems are not in true equilibrium. If we move the discussion of "state function" to the last paragraph of the lead, it allows us to describe Heat as it "really is" in the bulk of the lead, and conclude with Heat as it is treated in most elementary treatments of the subject. There is a certain logic to that.--guyvan52 (talk) 15:42, 3 April 2014 (UTC)... And, after reviewing process function and state function, the more I believe we should follow Dirac66s advice and include both links. Both are "strong" links, IMHO. The weak/irrelevant articles are process variable and state variable. Proper links do wonders for a WP article.

The terms in question have various usages, and are relative to the settings of particular problems. I think it better to just say what needs to be said without relying on links. The article on state function reads "In thermodynamics, a state function, function of state, state quantity, or state variable is a property of a system ". I favour saying that heat is not a property of a state without requiring the reader to link. I also am not impressed with the looseness of the wording "state function, function of state, state quantity, or state variable". I don't see that someone interested in heat needs to be dragged through that rather disorganized list, unless he happens to be your tenured professor in need of a tutorial; is he likely to follow the link? Also I am not keen on referring to a process function, because part of the idea of heat is that it does not have to be describable as a process function, if a process function is a functional of a continuous path of equilibrium states. For heat, the existence of such a path is not required. That article has one reference, to a mathematics textbook.Chjoaygame (talk) 16:51, 3 April 2014 (UTC)

"...; it is not a state function of a system that is in internal thermodynamic equilibrium." Maybe it's a state function of a system that is not in internal thermodynamic equilibrium?Chjoaygame (talk) 17:51, 3 April 2014 (UTC)

Is it state function or state variable?

Two active editors want a link to something regarding Heat's status as a not being a state variable, and one opposes on the grounds that the terminology is to vague. I surveyed google using both keywords equally often: (thermodynamics state function OR variable) and (thermodynamics state function OR variable)

• Five sites said state function:

1. Chemwiki
2. U.Omaha
3. Roane State
4. Chemistrytwig
5. Youtube tutorial

• Three sites said state variable:

1. Physics forums
2. PhysicsNet
3. Khan academy

I concede that none of our numbers are overwhelmingly large (3 editors and a sample of 8 google links). I also could not figure out how many sites do not establish a name for the concept. But given what we have, it seems that the WP article state function is spot on, not only in not using the title state variable, but in listing state variable as an appropriate synonym for state function. I vote that we keep the link to state function and focus on other aspects of the lead to Heat. Adding an extra link to process function may or may not be a good idea, but I see no reason to press the point. I am happy with only one link.--guyvan52 (talk) 19:01, 3 April 2014 (UTC)

Though many writers do not bother with such trivia, the logic of thermodynamics is that when one sets up a problem or an account of a phenomenon, one selects the independent variables of state for it. For that problem or account, one should not subsequently change them; there are very good reasons for this. Prigogine and Defay put it thus: "Those variables which are chosen to represent the system are called the independent variables, and all other variables which are in principle calculable in terms of them are dependent variables. It is important to remember that initially we have free choice of the independent variables, but once made we cannot change our choice arbitrarily in course of a problem."<Prigogine, I., Defay R. (1944/1950/1954). Chemical Thermodynamics, translated and revised in conjunction with the authors, by Everett, D.H., Longmans, Green & Co., London, p. 1.> Then Münster says one can define also state functions based on those state variables. One can choose to re-write things as a new account by for example a Legendre transform, and then one has a fresh set of state variables in the fresh account. For local thermodynamic equilibrium non-equilibrium thermodynamics the usual state variable set of classical thermodynamics is often expanded by addition of further state variables, such as flows, which are not state variables for classical thermodynamics. These points are not made in the article State function. It is not surprising that you found a mixed result in your Google survey.

I don't think any of this is important for the lead of the article on heat. The body of the article has a section on it, but that does not consider elaborately the terminology. Also I think one should not restrict the natural language for one's article by what one finds in, or by links to, other Wikipedia articles. One should focus on one's own article, and one's own reliable sources.

I am presumably the editor who you say is opposed to a link. My latest post gave the link you want, so I am not sure how you reach your conclusion.

But yes, I oppose shackling the surface language of the article by chaining it to a special terminological link, especially a link that might change in ways we cannot anticipate, and that has to be carefully chosen from several candidate links (what if someone merges them?). The various technical terms are refinements, for this article I would say verging on sophisticated refinements. I am happy to link, as I did, but not to shackle the language thereby.

What matters is that heat is not a property of a system's state of internal thermodynamic equilibrium. (You find it objectionable that there should be three of s in a sentence. The word property turns up prominently in many accounts of state variables or functions.) We can highlight this by saying that it describes a dissipative process.Chjoaygame (talk) 23:54, 3 April 2014 (UTC)

I stand corrected, you did favor the link state function but opposed the words 'state function' in that paragraph. Also, much of our confusion arose from the fact that I was initially working with the inferior link state variable, before I learned of state function which is not only a better link, but likely a better choice of words. I too was initially bothered by the fact that thermodynamics has variables (e.g. P and V) as well as functions of those variables (e.g. PV or even PV²), all of which clouds the discussion of whether they should be called state functions or state variables. As the not-so-wise Humpty Dumpty put it, When I use a word it means just what I choose it to mean...--guyvan52 (talk) 02:40, 4 April 2014 (UTC)

If this use of jargon (state function) in the lead is really objectionable, how about saying: An important distinction between heat and energy is that heat is not a numerical attribute of a system, or more precisely, heat is not a property of a system's state of internal thermodynamic equilibrium (see state function).--guyvan52 (talk) 03:01, 4 April 2014 (UTC)

temperature related

The new cover note of the article shows a problem. It points to a faulty entry on the dab list. The faulty entry is

"Heat, in physics, is a fundamental thermodynamic process in which an amount of energy flows spontaneously from hotter (higher-temperature) to colder objects."

The main fault is the presence of the misleading parenthesis "(higher-temperature)". This gives the, at-best superfluous, and more realistically, misleading suggestion that heat is tied to temperature.

A lesser fault is that the word "thermodynamic" is overspecialized. True, thermodynamics is especially concerned with heat, but does not have exclusive rights over it.

A lesser fault is the redundant phrase "an amount of" that governs the energy that flows.

The new cover note of the article is itself faulty because it ties heat too closely to temperature. The wording "temperature-related" might be defended legalistically by its vagueness, but vagueness is a defect, so that the defence of vagueness is merely legalistic and not substantial. The added comment about irreversibility is excessively detailed for a cover note. The justification offered for the change says that ″"thermal energy" may seem simpler even though less fundamental″; this is hard to understand and is not a proper justification.

A part of the justification offered for the new cover note is that it is to distinguish heat from thermal energy. Thermal energy is a tricky term, that is not well defined and is not really a phenomenon at all. It is a vague label. Transfer of energy as heat is a phenomenon, you can see it. Thermal energy is an explanatory concept, and a vague one at that. The cover note has no need to distinguish a phenomenon from an explanatory concept.

The new cover note seems like an attempt to impose a definition of the scope of the article, even to summarize the article, without the scrutiny that the lead gets.

I am not now undoing the new cover note because I think that might not be the best way to deal with it, but I think it is bad.Chjoaygame (talk) 19:00, 17 April 2014 (UTC)

Hi Chjoaygame. I understand that these wordings don't capture universal or fundamental definitions of heat, but that's not their purpose. The fact is that there are two articles called Heat and Thermal energy, and the purpose is for the average reader is to decide which concept they are reading about, and which one they would like to read about. The in-article link used to say {{About|a fundamental phenomenon of physics and thermodynamics in which energy flows spontaneously from hot to cold objects|for other uses}} and it had been changed to {{About|a simple physical phenomenon|for other uses}} which was completely uninformative as it could just as well describe dozens of other topics (in fact, arguably, heat is not one of the simplest among them). I'm trying to get it back to something meaningful and recognizable to the average reader, but many alternatives for doing so are possible.

In any case I'll try re-doing the in-article link wording to use some of the wording of the first sentence of the lede, without reproducing the entire sentence. I'll try the word "fundamental" in there to at least allude to the important distinction you point out in status between heat and thermal energy.

DavRosen (talk) 19:57, 17 April 2014 (UTC)

Thank you, Editor User:DavRosen, for these remarks.

Your new version seems to me much better. My main suggestion for improvement now is to put in a comma, to put the phrase "from a hotter body to a colder one" in apposition, as explanatory of the previous phrase "a fundamental type of transfer of energy", as distinct from a qualification of it. I would also like to see the wording "a fundamental type of" removed. It is more philosophical and detailed than I think is called for in this cover note. I think it unnecessary to try in this way to distinguish heat from thermal energy in this cover note, because I don't think the average reader will have 'thermal energy' in mind from the start. 'Thermal energy' is a kind of jargon that will occur more in the sophisticated reader's mind. I don't think we need too much saying how this article is different from other articles; that would be a mighty task. I think we just need to say what this article is about.

Okay, but I wouldn't want to suggest that heat means or is (merely) a "transfer of energy"; it's a particular type or mode or mechanism of such transfer (though we can't adequately summarize what characterizes that type here).
DavRosen (talk) 23:01, 17 April 2014 (UTC)

A tolerable compromise between preferences for spareness and philosophic detail.Chjoaygame (talk) 23:26, 17 April 2014 (UTC)

I wouldn't say that the version that read "a simple physical phenomenon" was "completely uninformative". It occurred in a context. The context was of the word "heat". People know more or less what heat is in a physical sense. The note just indicated that the physical sense was the one for this article, not for example the metaphorical sense of 'now I'm feeling the heat'. And it indicated that a phenomenon was the subject.Chjoaygame (talk) 22:16, 17 April 2014 (UTC)

Okay, okay, it was somewhat informative :-)
DavRosen (talk) 23:01, 17 April 2014 (UTC)

I would say, informative enough.Chjoaygame (talk) 23:26, 17 April 2014 (UTC)

As for the existing disambiguation entry, we can remove the parenthetical phrase from "hotter (higher-temperature) to colder", but the reader will probably still interpret "hotter" to mean "higher-temperature" -- or is there something else we could use that would provide a preferable interpretation of "hotter"?

DavRosen (talk) 20:17, 17 April 2014 (UTC)

Thank you for this. Yes, I would be happy to see removal of the parenthesis (higher-temperature). I am happy to let the reader insert his own ideas, so long as we haven't made some suggestion that would pre-empt or mislead him. I don't think we need to try to dictate his every passing thought.Chjoaygame (talk) 22:16, 17 April 2014 (UTC)

Okay, though I'm still not sure how leaving the meaning of "hotter" unstated helps anything. I'll also remove "thermodynamic" as you requested. I don't want to remove "amount of" because the use of the term heat doesn't necessarily merely state the occurrence of a process, but is also characterized by the amount (Q) of energy transferred by this occurrence of the process.
DavRosen (talk) 23:01, 17 April 2014 (UTC)

You have just above said "the reader will probably still interpret ″hotter″ to mean ″higher-temperature″". I think that's enough for the meaning of hotter. Removal of the parenthesis removes the misleading tie to temperature. Hotter doesn't just mean higher-temperature. It is relative to its context and means 'able to transfer heat to its colder neighbour'. As for 'amount of', I think the reader can work that out for himself without our aid. Again, I don't think we need to try to dictate every word that passes through the reader's mind.Chjoaygame (talk) 23:26, 17 April 2014 (UTC)

And "colder" presumably means "able to transfer/receive heat from its hotter neighbor"? Is this a circular definition of hotter and colder in terms of one another, just to avoid bringing in an additional concept like temperature (or entropy...) DavRosen (talk) 00:00, 18 April 2014 (UTC)

This is to guide the reader to the right article, not to abstract or summarize it. As for circularity, the idea is that changes of state are recognizable, and are here identifiable by changes in internal energy other than by work or transfer of matter. Or for a more general approach, hot and cold are words of the ordinary language that do not need definition in the top note of an article.Chjoaygame (talk) 04:56, 18 April 2014 (UTC)

Hi DavRosen. I agree with Chjoaygame. Although the circular language may sound odd, it seems to be the quickest way out of the conundrum arising from the fact that the reader expects definitions that are clear, technically correct, but also brief. Some sort of compromise is unavoidable, and your recent edits to the disambiguation page are appreciated.--guyvan52 (talk) 19:18, 19 April 2014 (UTC)

why?

"Why would heat transfer spontaneously from one body to another if we haven't said anything else about the bodies?"

This is the offered justification for the undoing of the previous edit, that more emphatically separated the definition of heat from the definition of hotter and colder, making it clearer that the hotter-colder idea is defined by dependence on the sense of the heat transfer. Neither definition offers an explanation of why heat transfer occurs.

In general, a definition of something does not offer to explain why it happens.

The explanation of the spontaneous character of heat transfer is rather deep, and is not part of the definition of heat. Non-zero heat transfer implies that the bodies stand in a hotter-colder relation to one another. If, apart from work and matter transfers, no energy transfers spontaneously, then one can say either that the heat transfer was of zero magnitude, or that there was no spontaneous energy transfer and therefore no heat transfer, as one prefers to speak. Either way, the hotter-colder relation is undefined. Then the bodies are said to be in a relation of thermal equilibrium.Chjoaygame (talk) 03:07, 22 April 2014 (UTC)

beginning the lede accessibly/usably vs foundationally/theoretically

It isn't necessary that the very beginning of the lede be driven by the most modern, general, or foundationally-pure definition of heat, nor necessarily limited to stating a subset of the necessary and sufficient conditions from such such a technical definition, nor necessarily avoiding mentioning any terms in a way that is pedagogic, predictive, or useful under limited circumstances but do not encourage the exclusive use of the most fundamental theoretical framework for thermodynamics.

I believe this is at the root of many of the disagreements we see for this and some other articles, especially those in thermodynamics.

In attempting to begin each article with such a general definition, we end up making this beginning inaccessible and obscure to the average reader. The average reader could benefit more, for example, from something enabling them to recognize heating in some simple situations and begin to be able to make predictions in such situations when they actually encounter them.

The most notable things for a nontechnical reader to know about, and be able to use, and relate to something else they know, are not always the same as the most notable things that a theorist or expert needs to know in order to understand the theoretical foundations of the field or which variables are primitive and which are defined in terms of which.

Also, prediction is useful and important even when you are not necessarily predicting an effect from its cause. If I have objects 1 and 2 (each at equilibrium etc) whose temperatures I've measured with a thermometer as T1 > T2, I can predict that if I put them in appropriate contact, heating will occur spontaneously, transferring energy from object 1 to object 2. This is a very useful prediction and a very notable "thing to know" about heating, even though the transfer is not caused by the temperatures themselves, and even though temperature is not more fundamental or primitive than heat, and even though today's most notable foundational or technical definitions of heat do not and should not define it in terms of temperature. And, yes, even though there exist other cases in which the temperature of a system as a whole is not even well-defined and yet heating can occur, and even though, in a subset of such cases, even the concept of local temperature or partitioning the system into small approximate-equilibrium or infinitesimal equilibrium cells doesn't always make temperature well defined or usable to predict heat.

Even beyond the first sentences, as it stands now (and in contrast to most other introductory treatments of heat, including probably many other wikipediae) a general reader of this article would likely close it without having learned that there are some simple (predictive) relationships among measured temperature and energy transfer via heating in some situations that he may encounter every day. He/she would not know that when he goes outside in the winter, his body spontaneously loses energy via heat, nor even that the concept of "heat" is in any way applicable or relevant to this phenomenon (aside from his possible preconceived conflation of heat with temperature), nor that energy will *not* similarly flow spontaneously in the other direction to give the energy back to him, nor perhaps that science has very much at all to say about this phenomenon that he encounters every day. Of course you and I know that there is relevant information in the article, but it is buried deeper and thus de-emphasized in favor of the more technical aspects that are applicable in the more general case rather than the simpler or more common cases.

Even in the lede we launch into engines before discussing any simpler situations that might be relevant for that person going out in the winter. Heat is an important and useful concept even if engines had never been invented or discovered. Engines are also of course a more complex example because there is much more than heating going on in an engine. Some of these complexities may have been brought in very early primarily in order to justify the more general/technical treatment itself

DavRosen (talk) 17:29, 22 April 2014 (UTC)

Well, it emerges that you would like to see big changes in the article, especially in the lead. I will need a few days to think about this.Chjoaygame (talk) 18:46, 22 April 2014 (UTC)

In the meantime, I have removed from the lead the chatter about engines, which has worried me for some time, that it was excessive.Chjoaygame (talk) 02:13, 23 April 2014 (UTC)

Having thought about what you write just above, I see it is about Wikipedia policy. I think it unlikely that I can respond usefully about that.Chjoaygame (talk) 22:00, 23 April 2014 (UTC)

Okay, do you mean that what I'm proposing may indeed be more consistent with wikipedia policy than what we have in this article today? Or that what I'm proposing is less consistent with, and thus would require a change to, WP policy? Or that you aren't certain which (if either) is consistent with policy and will leave that question to others? Or something else? DavRosen (talk) 13:58, 24 April 2014 (UTC)

I mean that I think it unlikely that I can respond usefully about it.Chjoaygame (talk) 22:08, 24 April 2014 (UTC)

Does anyone like this idea for modifying the lead?

In physics, heating is transfer of energy, from a hotter body to a colder one, other than by work or transfer of matter. It occurs spontaneously whenever a suitable physical pathway exists between the bodies.[1][2][3][4][5][6] The pathway can be direct, as in conduction and radiation, or indirect, as in convective circulation.[7][8][9] (Heating is a dissipative process. Heat is not a state function of a system. (reinsert below)

Kinetic theory explains transfers of energy as heat as macroscopic manifestations of the motions and interactions of microscopic constituents such as molecules and photons.

The quantity of energy transferred as heat is a scalar expressed in an energy unit such as the joule (J) (SI), with a sign that is customarily positive when a transfer adds to the energy of a system. It can be measured by calorimetry,[10] or determined by calculations based on other quantities, relying on the first law of thermodynamics. In calorimetry, latent heat changes a system's state without temperature change, while sensible heat changes its temperature, leaving some other state variable(s) unchanged; the terms latent and sensible are correlative.

Heat is a central concept in thermodynamics and statistical mechanics, and is also important in chemistry, engineering, and other disciplines. Heating is a dissipative process. Heat is not a state function of a system.

--guyvan52 (talk) 21:01, 24 April 2014 (UTC)

Not I.Chjoaygame (talk) 22:11, 24 April 2014 (UTC)

That makes the vote 0 to 1, as I shall abstain.--guyvan52 (talk) 14:46, 25 April 2014 (UTC)

I like moving down & clarifying the "not a state function" part as this is meaningless to the general reader. Something about microscopic constituents should stay because it is a good pedagogy for visualizing what heat can be (even if not in the most general case). Dissipative is important and slightly easier to understand than not a state function but could be explained.
Is this meant to address my concerns in previous section, or is it separate from that? DavRosen (talk) 17:23, 25 April 2014 (UTC)

Yes, this was meant to address your concerns in the previous section. But I must confess that I had trouble understanding your concerns. The lead as it now stands is acceptable to me -- all Wikipedia leads are compromises, so acceptable is the best we can ever get. I like the idea of clarifying phrases like "not a state function" but in thermodynamics, efforts at clarification can easily go astray. I believe this is because concepts like "heat", "temperature", and even "entropy" are just words, and words can have different meanings in different contexts. Defining (or describing) "heat" as energy that flows between objects of different temperature is good. Qualifying that with advanced concepts such as "ohmic heating" or reversible heat flow between substances of nearly the same temperature can quickly send the reader into an abyss of complexity that must be avoided. (In fact the only reason I wanted to include the non-state-function status of heat in the lead is that it is such a common misconception among students)

To reiterate, clarifying "not a state function" is a good idea. But I cannot support it until I see the actual words. I do like the idea of deleting "Kinetic theory explains transfers of energy as heat as macroscopic manifestations of the motions and interactions of microscopic constituents such as molecules and photons.". Among other things, not all thermal energy is kinetic energy. Moreover, it not "kinetic theory" but "quantum theory" that ultimately explains anything in the real world. But as I already stated, the lead is acceptable to me. (Is lede the British spelling?)--guyvan52 (talk) 00:48, 26 April 2014 (UTC)

At the risk of arguing with myself, I now see the need for some sort of statement informing the novice that heat and temperature must be understood at the microscopic level of randomly moving particles. Therefore, my proposed deletion of the sentence containing "kinetic theory" probably needs to be replaced by a suggestion that we look for a better way to express the concept.--guyvan52 (talk) 00:58, 26 April 2014 (UTC)

(Spelling it lede means one is very much au fait and with it. Spelling it lead means one is just ordinary. Lede is not ordinary English, British or not.)

I think that some mention in the lead of kinetic theory, or somesuch, is almost inevitable. If it is removed now I guess it very likely that someone will soon put it back, with some determination, with either of the words kinetic or statistical. Kinetic theory is good at explaining temperature for some problems, but heat is best considered as primarily a macroscopic thermodynamic concept I think. While kinetic theory can account for heat as microscopically diffusive transfer of energy, it is hard to see it as giving an account more easily accessible than is given by the more or less intuitive concept of macroscopic conduction. Kinetic theory is hardly the most obvious simple way to describe radiation. I don't think the summary use of quantum ideas makes heat transfer clearer to intuition. I think that in order to understand the quantum approach, one first needs to understand the macroscopic.

The phrase 'motions and interactions of microscopic constituents' intends to include the potential energies of particle interactions.

I would be unhappy to describe "heat as energy that flows between objects". It might give the impression that it started as heat in one object and ended as heat in the other. I would not be so unhappy to see it described as energy in flight, or as energy flowing, because these do not seem to me to suggest the impression of the just previous sentence. But I think there are some who would be unhappy with these as well.Chjoaygame (talk) 04:53, 26 April 2014 (UTC)

I don't think we want to immediately rewrite those first couple of sentences; they were constructed through a lot of negotiation to be just ambiguous enough not to outright contradict foundational views while still conveying at least a little bit of usable information to the general reader.

1. The first sentence is ("intentionally" in my view) loosely readable in at least two ways: as heat being the [perhaps "form of"] energy itself, and as heat[ing] instead being the transfer process/mechanism (which in turn transfers energy rather than being energy).
2. The first & second sentences together (again "intentionally" to me) allude to heat and a temperature difference co-occurring in some situations, without strictly implying that heat is caused nor defined by temperatures nor depends on temperature being a more primitive concept.
3. Ultimately I believe macroscopic thermodynamics is largely "explained" by statistical physics/thermodynamics (even without quantum mechanics) -- not just under the assumptions of simple kinetic theory. But I don't think mentioning the term kinetic theory itself adds anything for the general reader except a technical term that doesn't itself aid in the simplest summary of the concepts of heat.

I wasn't so much trying to elicit new wording as I was trying to start a discussion about the goals of the article and especially for the general reader who will not read deeply into it. My view is that foundational definitional questions that don't affect the predictions of thermodynamics nor actual outcomes of experiments may provide nothing understandable or usable to the general reader; rather they are a subject of great interest and importance to those among us with a deeper interest in thermodynamic theory. If it's absolutely necessary not to denigrate the most current or notable definitional formulation of thermodynamic theory, I would rather see such caveats in a footnote than see them constraining the entire approach of what's the most notable for the general reader to take away from the article.

DavRosen (talk) 03:13, 28 April 2014 (UTC)

BTW, one approach, which may or may not be helpful here, is to convey useful (but non-universal/non-foundational) information without the explicit caveats, but then, either immediately or even later in the section, say "More generally, ....". DavRosen (talk) 03:26, 28 April 2014 (UTC)

The "more generally" phrase is a good idea to keep in mind. But it is not a panacea. For example, "Heat is energy that spontaneously flows from hot to cold objects. More generally it can refer to other forms of energy transfer, such as energy delivered to conductor by passing current through it." The problem is that we are talking about two different definitions of the same word, not exceptions to one definition. In this case, I think the best solution is to take a long range approach and wait for Wiki glossaries or dictionaries to fill that gap. Whenever I look at a WP history page, I see that improvement has occurred over the years. I trust that this is also happening with Wictionary. Another place to fill such gaps is Wikiversity. Someday I would like to write a Wikiversity learning resource that "teaches" a Wikipedia article. Unfortunately I have years of projects with higher priority ahead of me.--guyvan52 (talk) 14:14, 28 April 2014 (UTC)

I don't think we should get too hung up on having the first sentence (or several) constitute a definition of heat in the most advanced and airtight way. Rather we should start with what ever conveys the largest amount of the most notable characteristics or characterizations of heat. By "conveys" I mean what the general reader will take away from it, not what we state that they don't know what to make of. In science, the ability to recognize instances of the concept that you may encounter or to use it to make testable predictions are important measures of how much notable information you've really absorbed about the concept. For example, if they know that A is at a greater temperature than B, then they can predict that appropriate contact will result in energy transfer from A to B as heating. Or vice-versa -- if this energy flow is occurring spontaneously then they can predict that, if they are able to measure a consistent temperature on both sides of the boundary, the temperature must be lower on the side receiving the heat. This is a phenomenon that the general reader can recognize and use to make predictions in situations he will encounter. Prediction can go in more than one direction among a set of variables and doesn't in itself imply the causation or definitional relationships among the terms or variables used. It isn't possible to immediately convey the causal or especially definitional relationships even though these are of paramount importance to an expert, who, by the way, can already recognize (and make predictions with) the aforementioned heat examples without necessarily digging down through the fundamental definitions themselves explicitly. The fact that it isn't the temperature itself that causes or defines the presence of heating (but rather both are caused by....) is a subtlety that the general reader is not yet equipped to appreciate in the first couple of sentences of the lede, so it shouldn't drive the content there. Constraining the initial content so as not to contradict what the expert knows most fundamentally may make the expert happy but is going to cause the general reader to take away less comprehension. The first couple of sentences shouldn't be targeted at the expert, who already knows far more than we could state there anyway. (Distinguishing heat from a transfer of matter may be another definitional subtlety that needn't appear in the first sentence; you can understand and use a lot about thermodynamics that isn't nullified even if you refer to a diffusive dissipative transfer of matter as a type of heat terminologically.) DavRosen (talk) 14:05, 30 April 2014 (UTC)

modify the lead?

I think also that the lead need to be modified. In particular, the actual definition is related just to the case where heat is transferred between two systems. In the general case, heat can also be:

• consumed or generated by a chemical reaction
• generated (or consumed? - I don't know) by a nuclear reaction.

Hence, I suggest this definition:

In physics, heat is defined as the contribution of energy consumed or generated because of a chemical or nuclear reaction or transferred between two systems or two parts of the same system, not attributable to work.

This definition is translated from it.wikipedia. Actually, in it.wikipedia it says "not attributable to work or energy conversion", but I think that heat can be seen as a particular energy conversion, for example "Heat of reaction" is generated by the conversion from chemical energy to thermal energy.
I agree that, if possible, it could be also clearer to give a brief definition of "dissipative process" and "state function", otherwise it is difficult for the common reader to understand.
Finally, regarding the sentence:

Kinetic theory explains transfers of energy as heat as macroscopic manifestations of the motions and interactions of microscopic constituents such as molecules and photons

It looks to me to much complex to stay in the lead. Or at least, it could be moved at the end of the lead, with the sentences related to the state function and dissipation. @Chjoaygame: Kinetic theory explains also the process of heat transferred by conduction; in fact we can think that during conduction the particles collide each other and during this collision they exchange "microscopic kinetic energy" (= thermal energy). --Daniele Pugliesi (talk) 00:18, 30 October 2014 (UTC)

Thank you for these comments.

There has been a consensus here that heat is as defined in the lead of the article. Your proposal goes radically and incurably against that consensus.

I agree that the sentences about state function and dissipation are rather technical and opaque. They are a compromise to partly satisfy some editors who want those concepts emphasized. I am inclined even to think that dissipative process is not the best way to express the matter. Considerable care would be needed to remedy this.Chjoaygame (talk) 01:54, 30 October 2014 (UTC)

I have now taken care of it.Chjoaygame (talk)

First of all, please read here:

"Editors may propose a change to current consensus (...)"

and:

"Editors who revert a change proposed by an edit should generally avoid terse explanations (such as "against consensus") which provide little guidance to the proposing editor (or, if you do use such terse explanations, it is helpful to also include a link to the discussion where the consensus was formed)"

Now, please concentrate to the issue: I raised more than one reason to say that the actual lead is not general enough.

It makes no sense to talk about "opinions", so I will look for reliable sources that give a clear and complete definition of heat. I invite also the other participants to the discussion to do the same: let's just pay attention to choose reliable sources and more than one, so we can realize which definition of heat is universally adopted. I think this is the wiki-way to approach the issue, if you have any other opinion please let me know. Thanks. --Daniele Pugliesi (talk) 19:36, 6 November 2014 (UTC)

• The problem is there exist an infinite number of types of potential energy that can be transformed into heat. Not just from nuclear and chemical reactions. If you get shot by a rifle, or drop a rock on your toe, that energy also turns into heat (eventually), but this is not a good reason to redefine the lead, because the energy in these processes, even after it becomes kinetic, isn't HEAT energy (yet) Or THERMAL energy (yet). A bullet or fission fragment has no temperature just because it is moving fast. Its kinetic energy must be "thermalized" to make a temperature, before heat can appear, and a bullet or fission fragment is not carrying "heat" or thermal energy.

  The reason is that heat is a special type of energy transferred down thermal gradients as dq = TdS, and you must set up a temperature and a thermal gradient before this entropy-increasing process can happen.

  Something irreversible, in other words, needs to be done to the energy before it becomes "heat." That is true also in chemical and nuclear reactions, which don't specifically release "heat" so much as fast particles. A chemical reaction does not release "heat" any more than a fission fragment or a bullet does. Rather, before "heat" appears, there's some necessary entropy to pay court to. There must be some randomization of direction of kinetic energy in a solid or gas that much happen first, before we make "heat." Just because "heat" is what we wind up with at the end, does not mean we should make a mistake of thinking "heat" is what we had, all along. This article is about what happens when temperature gradient has been established, and heat flows as a thermodynamic process, down that gradient. It's not about what happens as the rock is dropped on your toe, before impact. The heat from an impact or reaction is well after the mechanical steps you want to talk about, which (strictly speaking) are "pre-heat" energy transformations. There really isn't a name for them. But "heat" doesn't appear until late in this process. By that time, there are limits as to how much of your previous chemical or kinetic energy you can get back! SBHarris 21:25, 6 November 2014 (UTC)

• Thank you, Editor Daniele Pugliesi for lecturing me on my bad manners. I am glad to learn from you.

Going to your proposal, which I copy here from above for convenience: As I read you, you are proposing to change the present article's definition of heat to the following.

In physics, heat is defined as the contribution of energy consumed or generated because of a chemical or nuclear reaction or transferred between two systems or two parts of the same system, not attributable to work.

This definition is translated from it.wikipedia.

This may well be the view of the Italian Wikipedia, but it is not the consensus view here, as may be found out by reading this talk page over some years. So far, you give no hint that you have done that. Neither have you actually produced a fair survey of good sources to show which we should regard as reliable. Indeed, the only source so far that you have cited is the Italian Wikipedia. Wikipedia does not qualify as a reliable source, because that would be dangerously circular.

There are good reasons for the consensus here. In a nutshell, internal energy cannot be split consistently into heat and work and chemical constituent moieties. This is because heat and work describe processes of energy transfer, not states of a system, while internal energy describes a state of a system. You seem to have taken no notice of those reasons.

The definition you propose is naturally read to imply, even if only tacitly, that heat is a constituent moiety of internal energy.

There are of course, plenty of old-fashioned texts that do not use the foregoing strict definition of heat as a transfer quantity. In that respect they are not here considered to be reliable sources. As I have mentioned, to recognize a reliable source in a scientific area such as thermodynamics, one needs to compare a good range of potential sources.

I think it fair to say, in view of the many old-fashioned texts that use the word heat in more or less the ways you propose, that one cannot expect to find a "universally adopted definition" such as you suggest we seek. It would be very bad to try to reflect the various obsolete ideas in the present article as if they were of equal merit with the preferred and best. If you wish to write a section on obsolete ways of using the word heat, I suppose you might do so, explicitly recognizing them as obsolete. You would need to make it clear that from the viewpoint of the present article, the obsolete usages represent errors or confusions of thought in physics.

You also seem to want to put more in the lead about a dissipative process, and about a state function. The lead is a summary of the article, not the place for extensive detailing. As a matter of detail, following your suggestion, I have removed the word 'dissipation' and replaced it with the perhaps more controversial, but I think more accurate and appropriate word 'dispersal'. Dissipation really refers, I think, to conversion of bulk kinetic energy, and work, into internal energy, and of chemical potential energy into other internal energy, not heat transfer, which I think is more accurately described as dispersive. There is some objection to the term dispersion, but there is also good authority for it. Peter Atkins is perhaps the best authority for it, though it is also championed in Wikipedia by another group. The idea of dispersion in this context is good. In a microscopic picture, the energy is dispersed into all available microscopic degrees of freedom, as well as being dispersed into the widest reaches of space, subject to some constraints, such as phase change.

As for your proposal that the definition should be just about transfers not attributable to work, one should also consider that heat transfer is not definable in a transfer that carries matter with it. Therefore the definition should explicitly exclude transfer with matter as well and transfer as work. This point has been carefully explained in the article on the first law of thermodynamics, in which the various transfers are considered. Heat is transferred directly by conduction and radiation. Convection in general transfers internal energy, not heat. In the special case of convective circulation, the convective aspect transfers internal energy, which is collected and delivered by the direct mechanisms.

Thus, I am saying that from the viewpoint of the present article, your proposal would not make the definition more general, rather it would make it wrong in physics.Chjoaygame (talk) 21:36, 6 November 2014 (UTC)