Talk:Heat

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)

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)

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)