Talk:Heat/Archive 2

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Merger with Thermal energy

I have suggested that thermal energy be merged into this article, as it covers the same subject - the first paragraph of this page states heat is 'sometimes called thermal energy', and as I understand it, they are effectively the same thing. Why does thermal energy need its own article, which is no more than a stub anyway? Terraxos 06:03, 18 June 2007 (UTC)

As this article says, in thermodynamics, heat refers only to heat transfer. However, in common language, heat does mean thermal energy, and the history and overview sections of this article use that definition. I could support a merge. The way, the truth, and the light 10:05, 18 June 2007 (UTC)

I have performed a complex edit on these articles, please see the discussion at Talk:Heat (disambiguation). The way, the truth, and the light 20:51, 18 June 2007 (UTC)

It is true that people sometimes mistakenly interchange the words heat and thermal energy. However, this would be a very bad reason to merge them. It would be comparable to merging buffalo with bison or even to merging moon with green cheese. Cardamon 04:42, 20 June 2007 (UTC)

• "...we analyze the three forms of energy related by the first law of thermodynamics. These are heat, thermodynamic work, and internal energy. ... Today we recognize heat as a form of energy transferred by virtue of a temperature difference. ... Today we understand that heat is a form of energy rather than a substance." - Arfken, George (1984). University Physics. Orlando, Florida: Academic Press. ISBN 0120598604.
• "Heat is (internal) energy in transit due to a decrease in temperature between the source from which the energy is coming and the sink toward which the energy is going. ... When comparing the definitions of heat and temperature, it is possible to encounter a circular argument. For example, heat may be defined to be the flow of energy due to a temperature difference; and temperature may be defined as a property of an object which determines the direction of heat flow." - Besancon, Robert (1985). The Encyclopedia of Physics. New York: Van Nostrand Reinhold Co. ISBN 0442257783. — Omegatron 01:49, 21 June 2007 (UTC)

I'm not sure why merging would be bad. These topics are addressed in the same place in the above references. Heat is just thermal energy in motion? Both are measured in the same units, and are the same thing but in different contexts, no? — Omegatron 01:58, 22 June 2007 (UTC)

No. We may often want to think of thermal energy as not heat.

One textbook (but it is in a minority) that does recognise broader use of the word "heat" than just "energy being transferred" is the main statistical mechanics/thermodynamics text that I used at university (Waldram, The theory of thermodynamics, C.U.P., 1985; page 7). Here's what he says:

"... we find that when two systems are placed in thermal contact, energy frequently flows spontaneously from one system to the other, without action by the observer... Such a spontaneous movement of energy is called a heat flow, and heat entering one body from another is written q. The word 'heat' is simply a name for internal energy when we are thinking of the energy as randomised and free to move from one part of the system to another or between systems..."

However, he immediately checks this, because we may also want to think of the internal energy's ability to be channelled into useful work -- ie its use in a way which is organised and constrained, not randomised and free. Whether or not the energy is available to do useful work depends not on any property of the energy, nor of the thermodynamic system, but rather, on the temperature of any body or reservoir it can be placed in contact with. That is why Waldram immediately goes on to say that however,

"The use of this special term [heat, for internal energy] can be rather misleading. There is no special part of the internal energy which can be identified as the 'heat', and it must not be thought that energies entering as work and heat are stored differently inside the system."

When the term heat really becomes clear cut meaningful and significant is to distinguish energy which is flowing spontaneously from one system to another because of a temperature gradient, from energy which is being transferred in the form of work. The energy which is flowing spontaneously is always heat, and is important enough that we give it its own symbol q, so that we can write

ΔU = q - w (First law of thermodynamics).

where U is the internal energy, and w is the work being done by the system.

Because it is important to distinguish q and U -- they are different things -- this is the reason that most textbook authors prefer to use the word heat only when they are talking about q. And why Wikipedia should have separate, distinct articles for q and for U. (So no merger). Jheald 07:17, 22 June 2007 (UTC)

Thank You, Omegatron, for those extended quotes, both of which agree with what ScienceApologist said. I will quote one sentence from each of them (italics are mine). Arfken said "We recognize heat as a form of energy transferred by virtue of a temperature difference. .... " and Besancon says "Heat is (internal) energy in transit due to a decrease in temperature between the source from which the energy is coming and the sink toward which the energy is going." So both sources explicitly describe heat as (internal) energy as being that is transferred from one object to another, as distinct from energy that might be stored in some object at some particular time, i.e. as distinct from internal or thermal energy.

I hope that everyone here, except perhaps Terraxos, agrees that heat and thermal energy are different things. It is, however, very easy to mistakenly call thermal energy or internal energy "heat". (I did that myself until a few years ago.) One problem with using the same word for those two different quantities is that it can lead to confusing them and also, for those taking introductory physics classes, to writing incorrect equations. (Thermal energy and internal energy is typically represented with a U in recent textbooks, and heat is typically represented by some form of q. It will simply be easier for both teachers and students if the terminology matches up with the variables used. It would also be a good idea for Wikipedia's terminology to match up with that of science.

If heat and thermal energy were described in the same article, some people could be misled into thinking that they are the same thing, unless and until they read down to and understood the actual definitions of both terms. If the article ever becomes unclear or damaged (by vandalism or well meaning but mistaken edits) people could wind up thinking that heat and thermal energy are the same thing even after reading the article. So merging heat and thermal energy is bad because it would damage the effort to make Wikipedia a reliable reference, and do a disservice to those who try to learn from Wikipedia.

If you still want to merge thermal energy with something, merging it with internal energy, as TWTLATT suggested, would be a better choice. Cardamon 07:34, 22 June 2007 (UTC)

The very fact that we're having this discussion means to me that the three topics should be addressed in the same article. Not because they're the same thing, but because they're not the same thing.  ;-) — Omegatron 00:22, 23 June 2007 (UTC)

I'm sorry, but I just don't see how "the very fact that we are having this discussion" about merging things means that that they should be merged. I don't believe that there is any rule that all merge discussions must end in mergers. I also don't believe that there is any general principle that things that are different from each other should be merged because they are different. But, since the principles you have proposed don't seem to make any sense, perhaps these things are not what you meant? Cardamon 05:58, 23 June 2007 (UTC)

I'm referring to the content of this discussion, of course. If they are closely related enough that the difference between the two requires significant explanation on the talk page, a typical reader would probably have the same misunderstandings and want to read the same explanations in the article. — Omegatron 23:05, 24 June 2007 (UTC)

I rewrote the thermal energy article with three references. There is no need for a merge now. --Sadi Carnot 19:06, 28 June 2007 (UTC)

That doesn't change the reasons for the merger at all. No one has argued for it simply because Thermal energy is badly written. The way, the truth, and the light 06:38, 30 June 2007 (UTC)

And with that comment, Way-truth-light added templates saying It has been suggested that this article or section be merged with Thermal energy and It has been suggested that this article or section be merged with Internal energy. Yes, the former was suggested. It was rejected. The latter hasn't been suggested. If you're going to suggest it, Way-truth-light, suggest it on this discussion page, coherently. And then add the template, with an informative edit summary. -- Hoary 09:53, 30 June 2007 (UTC)

User:The way, the truth, and the light - I would like to suggest that, if you add a merge template, you probably shouldn't mark the edit minor, as you did here, here, and here. Edit summaries would be nice too. This suggestion especially holds for mergers that you have some reason to believe would be controversial. Cardamon 11:03, 30 June 2007 (UTC)

Moved from what is now Talk:Heat (disambiguation)

I just performed a complex edit that I think will solve the problematic proposed merger of Heat (now Heat (thermodynamics)) with Thermal energy. While the merger could still be done (I will restore the tags) I now think that it might be better to keep the articles seperate at Thermal energy and Heat (thermodynamics) as they are different concepts - the first is a kind of internal energy, the second the transfer of that energy. Because of this change, Heat should be a disambiguation. The way, the truth, and the light 20:37, 18 June 2007 (UTC)

Heat is not the same thing as thermal energy. Heat is the transfer of thermal energy. One is Q and the other is U. --ScienceApologist 21:08, 18 June 2007 (UTC)

That's exactly what I said above as a reason for keeping them as separate articles. The way, the truth, and the light 21:10, 18 June 2007 (UTC)

There exist no sources which confuse heat and thermal energy. Such a merger or confusion is inappropriate. --ScienceApologist 21:17, 19 June 2007 (UTC)

I think that The way, the truth, and the light's proposal is poorly considered. Heat is the transfer of thermal energy. End of story. --ScienceApologist 21:32, 19 June 2007 (UTC)

Here's how the main statistical mechanics/thermodynamics text I used at university puts it (Waldram, The theory of thermodynamics, C.U.P., 1985; page 7):

"... we find that when two systems are placed in thermal contact, energy frequently flows spontaneously from one system to the other, without action by the observer... Such a spontaneous movement of energy is called a heat flow, and heat entering one body from another is written q. (The word 'heat' is simply a name for internal energy when we are thinking of the energy as randomised and free to move from one part of the system to another or between systems. The use of this special term can be rather misleading. There is no special part of the internal energy which can be identified as the 'heat', and it must not be thought that energies entering as work and heat are stored differently inside the system.)

This matches how I would use the word: movement or transfer of energy = "heat flow" or "heat transfer"; the energy that is moving across the system boundary = heat.

So, to my mind, the opening words of Heat (thermodynamics) jar: "In thermodynamics, heat, symbolized by Q, is the transfer of energy..." -- IMO that is heat transfer. Jheald 23:26, 19 June 2007 (UTC)

(Also, I would tend to use q or ΔQ, rather than Q, for a finite amount of heat being transferred -- it's not a state variable). Jheald 23:26, 19 June 2007 (UTC)

The book I mention directly below uses Q for a finite amount of energy transferred, and q for an infinitesimal amount.--Starwed 07:17, 20 June 2007 (UTC)

Ok, I'm a bit confused here. By the form of ScienceApologist's words, I would think that he's arguing with with The way, the truth. But in fact, their position on this matter seems to be the same. (Namely, that Heat and Thermal Energy are distinct topics.) If the matter of contention is that there should not be a disambiguation page, I think the layman's understanding of heat is closer to the definition of thermal energy, and that there should be some note of this.

For reference, I found a section on this exact matter in Thermal Physics by Ralph Baierlein. In section 1.6 The meaning of words, he discusses the usage of the word heat.

Historically, the word "heat" has been used as a noun as well, but such use- although common- is often technically incorrect. The reason is this: there is no way to identify a definite amount or kind of energy in a gas, say, as "heat."

"Heat" as a noun flourished during the days of caloric theory, but by 1865 at the latest, physicists knew that they should not speak of the "amount of heat" in a gas. ...Usage that is technically improper lingers nonetheless...

Energy that is being transferred by conduction or radiation may be called "heat." That is a technically correct use of the word and, indeed, a correct use as a noun. Once such energy has gotten into the physical system, however, it is just an indistinguishable contribuation to the internal energy. Only energy in transit may correctly be called "heat."

--Starwed 07:10, 20 June 2007 (UTC)

It seems to me that (happily) that Baierlein quote is completely in tune with what I quoted from Waldram above: "There is no special part of the internal energy which can be identified as the 'heat' ... heat entering one body from another is written q".

Either way, they seem to agree on the semantic point I wanted to flag, that the "energy being transferred" is heat, not the "energy transfer".

Putting the language questions aside, the important physical point is that net heat transferred is not a state function of the system (dQ is not an exact differential) -- if the system can go in different ways from A to B, the change in internal energy U will always be the same; but one cannot uniquely say much of that internal energy change is represented by heat evolved or by work done. Heat evolution does not directly, independently relate to a change in any corresponding state variable (eg "thermal energy" (?) ). This is the crunchy point of real physics to bring out, the real point of misapprehension that needs to be identified and corrected. (Which AFAICS our articles at the moment don't really do.) Jheald 07:49, 20 June 2007 (UTC)

The current page now states that "Heat is the transfer of thermal energy." I agree with Jheald that this usage is incorrect. Heat, used as a noun, refers to the energy being transferred, not the process. I can't come up with a good wording this second, though, so thought someone else might take a stab at it? --Starwed 20:24, 21 June 2007 (UTC)

The current version, although it makes the sentance flow more smoothly, is a bit misleading.

In thermodynamics, heat is energy which spontaneously flows from an object with a high temperature to an object with a lower temperature.

This implies that it's possible to identify which energy in an object is heat. (It's implicitly defining heat as energy which will flow in a certain circumstance, implying that it exists even outside that process.) The reason for the tense chosen by Jheald was to elminate this ambiguity; it's only proper to refer to energy as heat during the thermodynamic process. Yes, this makes it hard to word the sentance nicely, but I don't think that's an excuse to decrease the accuracy of the statement. --Starwed 17:28, 22 June 2007 (UTC)

I think it's reasonable to say that the energy that will flow as heat is thermal energy, which is why the topics are connected. The way, the truth, and the light 06:42, 30 June 2007 (UTC)

Might it be helpful to describe heat as an "effect"? this would distance its association with "heat transfer" and could defined further as "an observed effect associated with a temperature difference"

I don't believe I've ever seen the word used that way, so probably not. --Starwed (talk) 14:09, 28 February 2008 (UTC)

The need is to distinguish heat from thermal energy, heat is measured by temperature in K, °C or °F etc., thermal energy in Joules. Anyone have a problem with this? --Damorbel (talk) 21:33, 10 January 2009 (UTC)

Heat, as a scientific concept, is measured in joules. Temperature is measured in K, etc. and is not the same thing as heat. Colloquially people might ask about the heat when they mean temperature, but from technical perspective this is an incorrect usage. Dragons flight (talk) 07:42, 12 January 2009 (UTC)

Dragons flight, you say "heat ... is measured in joules" and "temperature is measured in K", can you explain just what is measured by temperature? My point of departure being thermal energy is also measured in Joules. --Damorbel (talk) 10:10, 12 January 2009 (UTC)

It's tricky to define temperature in a satisfying yet simple way. A formal definition might be:

$T\equiv \left({\frac {\partial {S}}{\partial {U}}}\right)^{-1}$

Presuming constant volume and constant number of particles. Here T is temperature, U is the internal energy of the system and S is entropy. The SI unit of entropy is "joule per kelvin" (J·K⁻¹). Energy is measured in joule, so temperature should be in Kelvin.

The article about Temperature probably explains it better than I could hope to do though. (Or even better, a basic textbook on thermodynamics.)
—Apis (talk) 22:21, 14 January 2009 (UTC)

From another talk page

Slightly reformatted

Heat is thermodynamic

Are there any other sources which indicate otherwise? --ScienceApologist 21:30, 19 June 2007 (UTC)

Edit War

Please stop edit warring. You need to agree on one of the following:

1. It redirects to the thermodynamics version
2. It redirects to the thermodynamics version, with a see also
3. It redirects to the disambig

I'd recomment two, which is what I am implementing. Remember both of you, WP:3RR. Matt/TheFearow (Talk) (Contribs) (Bot) 22:09, 20 June 2007 (UTC)

I cleaned both articles. I assume the edit warring is over? --Sadi Carnot 19:08, 28 June 2007 (UTC)

Sections deleted?

It seems there's been a recent edit war on this article, so I'm wary of making any large-scale changes, but it seems in this edit a couple of sections (History and Overview) were deleted without any good reason that I see. Did they move somewhere else, or should they be restored to the current article? --Bob Mellish 21:26, 22 June 2007 (UTC)

Never mind, I found the sections over at Thermal energy. --Bob Mellish 21:31, 22 June 2007 (UTC)

I fixed the mess. Someone had moved the history of heat section to thermal energy. I moved this back and rewrote the thermal energy article. --Sadi Carnot 19:09, 28 June 2007 (UTC)

Cleaned this article and thermal energy article

I don't know who messed (or mixed up) the heat, thermal energy, heat transfer, pages (e.g. put the history of heat into the thermal energy page, etc.) but I will quickly clean up the mess. Each term has a distinct meaning, internal energy was essentially defined by Rudolf Clausius in the 1850s (although he built on some shoulders). --Sadi Carnot 04:15, 28 June 2007 (UTC)

Sadi, most of the material you have put back is about heat in the broader sense of energy that is randomised and free to move from one part of the system to another, and so is more appropriate under thermal energy. This article is about the narrower concept of energy that actually is in transit from one system to another.

If we are trying to keep these two ideas distinct, with distinct different articles, then I suggest your move back was misguided. Jheald 10:26, 28 June 2007 (UTC)

Jheald, the two sections I moved back are (1) a three paragraph overview section (an overview of heat) and (2) a history of heat section (that I wrote). This article is about heat, plain and simple. I also re-wrote the thermal energy article with three references; over an article that had no references. The thermal energy article has been a sore thumb here for about two years. It is basically a negligible topic (term) that his not used greatly. With three references, it should stabilize now. --Sadi Carnot 18:50, 28 June 2007 (UTC)

Why not merge the three? — Omegatron 01:06, 29 June 2007 (UTC)

In short, heat is its own topic, it has 5,000 year history; second, thermal energy is an obscure term, with its own peculiarly meanings (not equivalent to heat); third, heat transfer is a subject taught in college; also, and I don't know what else you are referring to but let's just call this a wrap. All of this mess stems from the thermal energy page, a problem that I have now fixed. Thanks: --Sadi Carnot 02:03, 29 June 2007 (UTC)

Moving the general information to the heat article says that heat is a more fundamental topic than thermal energy, which is nonsense using the narrow definition of heat. It's like talking about electric current without mentioning electric charge. If the thermal energy article is unused, it's an indication that the information probably should be merged. The way, the truth, and the light 06:35, 30 June 2007 (UTC)

Opening definition

The first line currently has the definition:

In thermodynamics, heat, typically symbolized by Q, is energy transferred from one object to another object.

IMO this is poor, principally due to ambiguity, because it could be interpreted to mean any energy transferred from one object to another object is heat. Rather, some energy transferred from one object to another object is heat, but some energy is transferred as work.

The previous version said "thermal energy which is transferred..." I appreciate this isn't ideal either, but it is necessary to identify what makes the contrast between heat and work, which the word "thermal" at least pointed to. Jheald 10:17, 28 June 2007 (UTC)

Jheald, that is a text-book definition (a section that I wrote). If you want to replace it with another sourced (textbook) definition then please do, but make sure that it has consensus with the other definitions in that section. Secondly, we want to avoid recursive definitions; thermal = heat, thus we cannot define heat = heat energy in transit. In any event, I have tweeked the intro per your request:

In thermodynamics, heat, symbolized by Q, is defined as energy in transit or more specifically as energy transferred from one object to another object due to a temperature difference.

I hope this is better? --Sadi Carnot 18:57, 28 June 2007 (UTC)

I also would prefer it to say thermal energy, so that the opening sentence would clarify the relationship between heat and thermal energy. I have made that change. Also, the transfer does not have to be due to a temperature difference; it can be due to a heat pump. Here is a quote from a textbook on thermodynamics by a leading thermodynamicist: ... We first recall that in both the sciences of mechanics and electricity we are much concerned with the concept of energy. Energy can be transferred to a mechanical mode of a system. such a flux of energy being mechanical work. " Mechanical work is typified by the term -PdV (P is pressure, V is volume) ... These energy terms and various other mechanical and electrical work terms are treated fully in the standard mechanics and electricity references. But it is equally possible to transfer energy to the hidden atomic modes of motion as well as to those which happen to be macroscopically observable. An energy transfer to the hidden atomic modes is called heat. ..." This is from page 7 of Thermodynamics by H.B. Callen, ISBN 0 471 13055 4. Of course thermal energy means the amount by which the energy of these "hidden atomic modes" exceeds what they would have at absolute zero. With this change, the definition is still not quite the same as Callen's (his allows for energy taken as work from one object to be transferred to another object as heat. Friction would be an example.), but it is closer.Cardamon 21:34, 28 June 2007 (UTC)

Cardamon, "what you prefer" and what is preferred by textbooks are two different things. Moreover, Callen's definition does not say "thermal energy" transfer; its says "energy" transfer. This is a no-brainer. Take a look at the section Heat#Definitions (which I wrote); the word "thermal energy" is not used. My personal collection of heat, thermodynamics, and thermal physics, and thermal science books and textbooks is up to about 135 now; my goal is to get the count up to 200. Last week, for instance, I bought an original $550 dollar (US) copy of Clausius’ 1879 Mechanical Theory of Heat (it smell beautiful!).

In short, thermal energy not a common word and has very little meaning; it is not found in Perrot’s A to Z of Thermodynamics, nor in the McGraw-Hill Dictionary of Engineering, nor in the McGraw-Hill Concise Encyclopedia of Chemistry, nor in Clark’s The Essential Dictionary of Science, nor in Gribbin’s Q is for Quantum – an Encyclopedia of Particle Physics, nor either of the Oxford’s Dictionary of Physics, Dictionary of Science, or Dictionary of Chemistry. I am going to replace the “what you prefer” definition, with what the Oxford Dictionary of Physics prefers:

Heat – the process of energy transfer from one body or system to another as a result of a difference in temperature (Oxford Dictionary of Physics, 2005 ed.).

This is the most accurate, consise, and common definition. I could easily add 10-20 more references to support this definition. Heat and its meaning has long and illustrious history, soaked with confusion (e.g. phlogiston, caloric, fire air, entropy, etc.); adding unfounded descriptors to a modern encyclopedia does not help the matter. In sum, please do not mix up the term “thermal energy” with heat; doing so will only constitute original research. Thanks for your cooperation: --Sadi Carnot 23:40, 28 June 2007 (UTC)

Sadi, the term "heat content" has an illustrious history in thermodynamics, also, and is why enthalpy has the symbol H. However, an object cannot have "heat content" (ie, there is no such thing) if you insist on defining heat only as a quantity entering or leaving a system, but never residing there to qualify as a "content." In truth, once the word-Nazis got done with heat in thermodynamics (quite recently) and decided that "heat" had to be transitive form of energy or else not exist at all with the same name (and thus, you weren't allowed to use it or picture it or draw it, on pain of death, you nasty little boy), they were finally left with the big problem of what to call "heat," once it wasn't going anywhere, and had arrived at its destination. And the solution they chose wasn't as simple and direct a solution as to what to call your aunt Sue after she's traveled to your house, and put down her bags. So they came up with "internal energy" and "enthalpy" (and occasionally, even "thermal energy"). But these are all fairly artifical and none of them are very intuitive. Certainly, none is as intuitive as "heat content." Heat flows into an object which starts at absolute zero, and finally results in it having a heat content, when the flow stops. Which content is (surprise) a sort of internal energy due to heat (see thermal energy) plus some part of the original heat which disappeared into PV work, but which can be recovered as heat (if you like), if you cool the object again. Heat isn't conserved, but this is no excuse to turn your back on it and pretend it doesn't exist AT ALL, once it becomes part of a system like your bathtub water. "Oh, we added heat to the water to make it hot, but once we got done, there's no heat anymore in the hot water, dear. It's enthalpy." Riiiiight. And we wonder why children don't trust us. For my part, I think it's too bad that the chemists didn't make better choices, instead of making up new words. Chem students hate "enthalpy" from the first day they hear it, suspecting a basically unnecessary and illogically-introduced pleonasm. And you know what? They're right. Heat content, defined as U + PV, is what it should have remained. SBHarris 02:42, 29 June 2007 (UTC)

SB, I think by "heat content" you are referring to heat capacity and specific heat work of Joseph Black and Antoine Lavoisier? But, in modern terms you are correct it does usually refer to enthalpy. Later: --Sadi Carnot 03:34, 29 June 2007 (UTC)

No, I really mean the heat content. For an object, this is the integral from absolute zero to T, of the quantity C(T)dT. That C(T) is the heat capacity-- the function which falls to zero as you close in on absolute zero, according to Debye, etc. It's dQ/dT. If you want the total heat content of an object, you obviously need to integrate C(T).SBHarris 06:46, 29 June 2007 (UTC)

SB, according to Perrot's A to Z of Thermodynamics, c = dQ/dT is the definition of heat capacity, also called thermal capacity. --Sadi Carnot 04:26, 2 July 2007 (UTC)

I'm sorry that the "word Nazis" won, but in modern science heat is defined as energy in transit, and "heat content" got replaced by more precisely defined terms (although I wouldn't be surprised to hear that "heat content" is still used in some jobs, same as "muriatic acid"). I'm also sorry that the second is now defined in terms of the hyperfine transition of Cs-133 instead of the astronomical day, but science has to move on. We have to use the currently accepted, verifiable definitions. --Itub 09:19, 29 June 2007 (UTC)

Sadi - Here are a couple of points I'd like to make:

1. The definition you found does an admirable job of emphasizing that heat involves a transfer of energy. (I would be happier with it if it said that heat is energy that is transferred. As it stands, it implies that heat is a kind of process rather than that heat is a kind of energy.)
2. More importantly, the definition: " Heat – the process of energy transfer from one body or system to another as a result of a difference in temperature (Oxford Dictionary of Physics, 2005 ed.)" seems to exclude heat transferred by a heat pump. Nonetheless, if you use a heat pump to heat a house, or an airconditioner to cool a house, heat is transferred against a thermal gradient.
3. I'm not married to the term thermal energy. Internal energy might be better. However, it is important to note that heat is energy transferred to, or from, what Callen called "hidden atomic modes", rather than to macroscopically observable degrees of freedom. Again, the definition you prefer does not explicitly say this. This should be said, preferably in the first sentence, but certainly in the first paragraph.
4. There is nothing original about points 2 and 3, nor are they out of date.

Thank you for your understanding. Cardamon 01:08, 29 June 2007 (UTC)

Cardamon, point #1 is fine if you want to change that. As to point #2, the Oxford definition still holds: heat is energy transferred from the cold body to the hot body via energy in the form of work input (heat pump). As to point #3, please stop trying to mix terms together: Thermal energy now has is own article with three references; it is a very obscure term; internal energy, however, is a state function, the simplist of which is the first law of thermodynamics, the mathematical statement of which is given by:

$\mathrm {d} U=\delta Q-\delta W\,$

where $\mathrm {d} U$ is the infinitesimal increase in the internal energy of the system, $\delta Q$ is the infinitesimal amount of heat added to the system, and $\delta W$ is the infinitesimal amount of work done by the system on the surroundings. In other words, internal energy is a function U = f(Q,W,chemical potential,external forces, etc.). I hope this helps? --Sadi Carnot 01:55, 29 June 2007 (UTC)

Sadi, not only am I not trying to mix terms, my original purpose in these articles was to prevent a damaging merger of heat and thermal energy. I agree that internal energy is the standard term, and was a little surprised to see Wikipedia placing so much emphasis on thermal energy. I actually do prefer to talk about internal energy rather than thermal energy. If I used the term thermal energy, it was because I started out here by talking to people who were using the term thermal energy. I am not pushing for a merger of thermal energy and internal energy (it was proposed by User:The way, the truth, and the light); I just feel that it would be less damaging than merging heat and thermal energy. And yes, I do agree with the first law of thermodynamics. :)

I agree that you can call the internal energy a state function. However, as the internal energy article also points out, from a statistical mechanical point of view, internal energy is the sum of the energies of many things that cannot be seen with the naked eye (i.e. microscopic degrees of freedom, which are what Callen meant by "hidden atomic modes") including the motions of nuclei, bond bending/ distortion of orbitals, excited electronic states, and so on. . Now I'd like to modify my point 3.

3' I would still like the article to point out in the introduction, in some way, that, for heat, the energy that is transferred from one object to another is internal energy rather than, say, mechanical energy. Cardamon

Sadi Carnot is completely right: heat is a process, not a kind of energy. you want internal energy or enthalpy for that. The heat pump is a good example of why it is important to keep to the standard definitions rather than folk definitions. Heat pumps to not cause heat transfer against the temperature gradient, but raise the internal energy of a fluid by doing work on it. This is all basic, first year undergraduate thermodynamics. MAG1 10:10, 29 June 2007 (UTC)

Incidentally, the quote from Callen's book is "An energy transfer to the hidden atomic modes is called heat. ...", which directly contradicts point 3, above. MAG1 10:16, 29 June 2007 (UTC)

MAG1 - First, I would like to point out that Sadi does not seen to have a problem with saying that heat is energy that is transferred. Calling heat energy helps a beginner understand why heat can be measured in the same units as energy, and why you can add heat to internal energy. Calling it a process doesn't.

While it is true that all heat pumps have internal mechanisms, they do not all have fluids. (Don't forget about Peltier effect coolers.) Internal mechanisms aside, when heat pumps are considered as black boxes (and in thermodynamics modeling things as black boxes is common) their net effect is indeed to use electrical or mechanical energy to do heat transfer from a lower temperature region to a higher temperature region.

The Callen quote doesn't really contradict my point 3; it basically is my point 3. But perhaps you were pointing out that it doesn't follow my point 1? Cardamon 10:40, 30 June 2007 (UTC)

Sadi Carnot can speak for himself, but confusing heat and internal energy does not help the reader, but misleads him. As Sadi said internal energy is a state function whose value for a system can be changed by the processes of heat and work (hence Callen's comment that heat is a transfer of energy): internal energy and heat are two different things, one is the energy possessed by a system, the other is the energy transferred over its boundary. As to the heat pumps, ok strike out fluid, put in system, the thermodynamic process is the same where internal energy is being changed through work. Work is a different process from heat. As I said earlier, this is all basic stuff. What should happen with mergers is for thermal energy to be deleted and a suitable note put in the internal energy page. MAG1 11:23, 30 June 2007 (UTC)

Uh - you do understand that I am against merging heat with anything, don't you? Cardamon 11:47, 30 June 2007 (UTC)

Yes, heat is not internal energy, and neither is it work. I am not claiming that heat is either of those things. Cardamon 11:34, 1 July 2007 (UTC)

is transferred vs. being transferred

Up at the top of the section, the point is made that the word heat should be applied only to energy while it is being transferred. The article still states that heat is energy which is transferred. Is there any objection to clarifying the opening sentance in this manner? Repeating what I wrote at Talk:Heat (disambiguation):

For reference, I found a section on this exact matter in Thermal Physics by Ralph Baierlein. In section 1.6 The meaning of words, he discusses the usage of the word heat.

Historically, the word "heat" has been used as a noun as well, but such use- although common- is often technically incorrect. The reason is this: there is no way to identify a definite amount or kind of energy in a gas, say, as "heat."

"Heat" as a noun flourished during the days of caloric theory, but by 1865 at the latest, physicists knew that they should not speak of the "amount of heat" in a gas. ...Usage that is technically improper lingers nonetheless...

Energy that is being transferred by conduction or radiation may be called "heat." That is a technically correct use of the word and, indeed, a correct use as a noun. Once such energy has gotten into the physical system, however, it is just an indistinguishable contribuation to the internal energy. Only energy in transit may correctly be called "heat."

--Starwed 13:00, 3 September 2007 (UTC)

ScienceApologist

I have been away for a few weeks, but I see that this whole mess caused ScienceApologist to quit. Hopefully he will come back? In any event, let's all try to stick to standard textbook articles and definitions and to stay away from drastic page moves, mergers, section re-pastes, or original research, etc., just because one or two Wiki newbies doesn’t understand a term or whatever. Thanks: --Sadi Carnot 00:07, 29 June 2007 (UTC)

No merge of thermal energy, internal energy, and heat

There seems to be some kind of confusion on this page (for one or two editors (basically User: the Way)) who still think that these terms (or possibly others) should be merged? From my point of view, it is obvious that any merging of these terms is clearly ridiculous. To clarify that other countries agree with me, I have comparatively posted the related countries’ articles below:

Thermal energy
de:Thermische Energie
el:Θερμική ενέργεια
es:Energía térmica
fr:Énergie thermique
it:Energia termica
he:אנרגיה תרמית
pl:Energia termiczna
ro:Energie termică
ru:Тепловая энергия
sv:Termisk energi

Internal energy
cs:Vnitřní energie
de:Innere Energie
es:Energía interna
fr:Énergie interne
id:Energi dalam
it:Energia interna
he:אנרגיה פנימית
lt:Vidinė energija
hu:Belső energia
nl:Inwendige energie
ja:内部エネルギー
no:Indre energi
nn:Indre energi
pl:Energia wewnętrzna
pt:Energia interna
ru:Внутренняя энергия
sk:Vnútorná energia
sl:Notranja energija
fi:Sisäenergia
vi:Nội năng
uk:Внутрішня енергія
zh:内能

Heat
ar:حرارة
bg:Топлина
ca:Calor
cs:Teplo
da:Varme
de:Wärme
el:Θερμότητα
es:Calor
eo:Varmo
fa:گرما
fr:Chaleur
gl:Calor
gu:ઉષ્મા
ko:열
hi:उष्मा
io:Kaloro
it:Calore
he:חום (פיזיקה)
lv:Siltums
ln:Eyángala
ml:താപം
nl:Warmte
ja:熱
pl:Ciepło
pt:Calor
ru:Тепловая энергия
scn:Caluri
simple:Heat
sl:Toplota
fi:Lämpö
sv:Värmemängd
tr:Isı
yi:היץ
zh:熱量

The main editor causing the issues here seems to be User:The Way. His last edit, where he changed (a textbook referenced section) "so an object cannot possess heat" to "so objects do possess "heat", clearly disqualifies him from any kind of understanding of the related subjects (also note his edit warring and recent blocks). User:Cardamon seems to be in agreement with me; User:Omegatron seems to want to merge all three of them?; and User:MAG1 wants to delete thermal energy. If any other users still have some kind of merge issues, please state your case below, in specific terms, so we can discuss the matter (gain consensus) in an organized fashion. Thanks: --Sadi Carnot 03:38, 2 July 2007 (UTC)

You're lying. I did not remove any references, you misrepresented my edit above by omitting the word not (in so objects do not possess "heat" ), and I believe it was User:Omegatron that proposed the multiple merge, not I. The way, the truth, and the light 08:38, 2 July 2007 (UTC)

Sadi- While Way did make an edit that that said "so objects do possess heat", less than a minute later he made another edit which corrected that to "so objects do not posses heat". So, I suspect that deleting the word "not" was just a temporary editing mistake. And Way, Sadi did not say you changed any references, he said that you changed part of the article that had a reference.Cardamon 10:00, 2 July 2007 (UTC)

Thanks, I didn't see the second edit; but, in any event, calling my efforts to dig through the thermal physics textbooks to clean the said article "non-sense" (twice) is non-Wikipedia like, let alone unfounded. --Sadi Carnot 14:45, 2 July 2007 (UTC)

Straw poll

• No merge (this shouldn't even be a discussion?) --Sadi Carnot 04:39, 2 July 2007 (UTC)
• No merge. What's next, merging letter with mail and envelope? --Itub 05:42, 2 July 2007 (UTC)
• No merge - Most physics textbooks describe heat and thermal energy as two separate concepts. Dr. Submillimeter 08:55, 2 July 2007 (UTC)
  • No one's disputing that. But those physics textbooks describe both concepts in the same place at the same time. That's why I suggested merging them here, as well. — Omegatron 00:07, 3 July 2007 (UTC)
• No merge of heat with either thermal energy or internal energy. Cardamon 09:29, 2 July 2007 (UTC)
• No merge Jheald 13:43, 2 July 2007 (UTC)

I removed all the merge tags. End of straw poll. As I wrote in my edit summaries, current editorial environment isn't conducive to a merge. --HappyCamper 12:57, 2 July 2007 (UTC)

Good work everyone. From above, Hoary is in agreement with us. We seem to have consensus; let us all move on to better use of our time. Thanks: --Sadi Carnot 14:45, 2 July 2007 (UTC)

• Strong no merge I didn't finish reading the talk page yet but I find even addressing the issue way out there. We need to recognize colloquial usage through disambiguation and explanation but heat and thermal energy are important and very distinct physics concepts. Personally I choose to think of heat as thermal energy flux. I noticed that some of the misunderstandings here arose from textbook author's efforts to address the colloquial usage or use it to explain the scientific definition in more accessible language. For the scientific definition look for where they define it rigorously. Yes, argument over. --Nick Y. 20:53, 2 July 2007 (UTC)

Thermal energy

This talk page is turning into the Wikipedia Original Research Center on Thermal Energy. As far as I know, I am the only one who has taken the time to add references to the thermal energy page (and all 13 of the references on the heat page, except the Egyptian gods reference). Thus far, I’ve checked 5 scientific encyclopedias, 6 scientific dictionaries, 4 thermal physics textbooks, and 4 physics textbooks and 6 chemical thermodynamic textbooks and over a dozen thermodynamics textbooks. In over 90% of the indexes, the term is not found; in the dictionaries and encyclopedias (save Britannica) the term is not found. In two physics books, it is used as a synonym for the mechanical energy of a system that is converted into internal energy via friction. Cengel and Boles’ 2002 Thermodynamics – an Engineering Approach is the only textbook to give an explicit definition (pg. 17-18). In short, they define thermal energy, via bold text (definitions), as a portion of internal energy, as such:

Internal energy (defined)

Internal energy – the sum of all microscopic forms of energy of a system. It is related to the molecular structure and the degree of molecular activity and may be viewed as the sum of kinetic and potential energies of the molecules; it is comprised of the following types of energies:

Type	Composition of Internal Energy (U)
Sensible energy	the portion of the internal energy of a system associated with kinetic energies (molecular translation, rotation, and vibration; electron translation and spin; and nuclear spin) of the molecules.
Latent energy	the internal energy associated with the phase of a system.
Chemical energy	the internal energy associated with the atomic bonds in a molecule.
Nuclear energy	the tremendous amount of energy associated with the strong bonds within the nucleus of the atom itself.
Energy interactions	those types of energies not stored in the system (e.g. heat transfer, mass transfer, and work), but which are recognized at the system boundary as they cross it, which represent gains or losses by a system during a process.
Thermal energy	the sum of sensible and latent forms of internal energy.

This is the most rigorous and explicit definition of thermal energy I have been able to find in contrast to those (on this talk page) who use it in a loose sense to argue whatever point they are trying to win. In sum, heat Q, work W, and internal energy U are the main (and measurable) topics of discussion in science; thermal energy is not. --Sadi Carnot 03:49, 3 July 2007 (UTC)

Baloney. Sitting here, I've pulled two random texts off my shelf, published half a century apart. The first is Myers, Analytical Methods in Conduction Heat Transfer (2nd Ed. 1998, AMCHT pubs, 1st edition, McGraw-Hill). A standard engineering text in the title subject. Here on page 3:

STORAGE IN A SOLID: Thermal-energy storage in a solid occurs when its temperature increases with time. ... dE/dt = ρVC dT/dt etc.. But fear not, Myers is defining thermal-energy stored as the old thermodynamic ΔU. Which is fine. But he's not afraid to call it "stored thermal-energy," since that's what it is. Sitting next to this is my old handy 1958 Handbook of Physics by Condon and Odishaw. The Chapter 1 of the Principles of Thermodynamics section, written by Edward Condon himself, does not bode well for a definition of heat which is strictly limited to heat transfer: "1. The Nature of Heat. Heat is a form of energy associated with random and chaotic motions of molecules of which matter is composed." Simple enough, and sounds pretty much like thermal energy, does it not? Condon does not define a thermal energy, but he does (as is standard many places) use the term enthalpy interchangably with the term "heat content." And while I know it must have hurt you terribly to see the term "thermal energy" used by the Britannica in more or less the way Myers does, the whole thing is not some plot by Myers and Condon and the Britannica and me, to make your life miserable, or win arguments here. I am simply refusing to pony up to the idea that even in science, definitions sometimes are not agreed upon, by all experts. Something that is obvious to me, anyway (you should see the arguments we've had about mass as used by physicists). Anyway, that's all there is to it. You may wish it was otherwise, but it's not. SBHarris 11:43, 3 July 2007 (UTC)

SB, firstly I have no problem with Britannica’s definition of thermal energy, which why I added it as reference to the thermal energy article. I have a problem with definitions based on random User opinion (ones that aren’t sourced). Second, why don't you add your definition (with reference) to the thermal energy article? Third, "heat content" is a descriptor of enthalpy, I dont' think anyone is arguing this. --Sadi Carnot 23:04, 5 July 2007 (UTC)

If I'm not mistaken, YOU are arguing it. Your article now says that an object "cannot possess heat" but can have a "heat content." Which is plainly contradictory and logically nuts. Contains and possesses are synonyms in English. If an object DID possess heat, it would certainly contain it. How could an object "contain" anything without also "possessing" it?? So you need to straighten this out in the LEAD section, as many people are trying to tell you. SBHarris 05:06, 12 July 2007 (UTC)

There we go, I’ve added this nice clarifying table to heat, energy, internal energy, and thermal energy. I hope we can all move on to other topics and not further clog up the heat-talk page about all of these un-related topics. --Sadi Carnot 05:04, 3 July 2007 (UTC)

Nah, you're not done, yet. You forgot to notice that your table doesn't agree with the definition of internal energy given in the Wiki on the subject, which exempts rest energy from the definition, and thus surely must also (therefore) exempt nuclear bond energies. Nowhere have I read that internal energy of a thing is the energy needed to disassemble it into (say) free protons and neutrons, widely spaced. But it would have to be that, if we followed your table. Instead, U is usually defined as the amount of energy needed to disasemble it into neutral atoms, widely spaced (this is the bond energies, with heat distributed over kinetic and potential modes of vibration in solids, etc). U (although the Wiki does not say this explicitly) basically the total binding energy of a system, at the atomic level (not the nuclear level). And it is, of course, a function of temperature. SBHarris 11:43, 3 July 2007 (UTC)

Now, you're twisting things around more than is there; for instance, internal energy = "energy needed to disassemble it into (say) free protons and neutrons". This is negligible detail (and would require further discussion to analyze and explain each situation), i.e. most thermodynamicists don't study nuclear reactions (a few do), but the laws of thermodynamics still apply and internal energy is the center piece of the first law. In any event, further discussion would be needed to argue every little detail. Short on time (presently), please consult the referenced textbook if you have further issues. --Sadi Carnot 23:04, 5 July 2007 (UTC)

Nuclear bond energies are not "negligable details." In fact, they are larger than all the other energies put together in the ordinary object. Your text contradicts the Wikipedia definition of internal energy. Why would I want to consult it? I can as easily find you a text which says something else. Wanna bet? SBHarris 05:06, 12 July 2007 (UTC)

Did you just copy a table verbatim from a book? — Omegatron 06:09, 4 July 2007 (UTC)

The table is shortened synopsis of two pages worth of discussion, but is accurate according to the source (in other words I did not add any extraneous conjectures in). --Sadi Carnot 23:04, 5 July 2007 (UTC)

The problem with the table is that it contradicts several other articles. It's just one editor's definition really. We should gain a consensus from standard texts on thermodynamics.

For one example, look at sensible heat. Your table defines it in terms of kinetic energy. However, the sensible energy article defines it as potential energy. If potential and kinetic are equivalent, they lose all meaning. The thermal energy article, the sensible energy article, this heat article, and all others that are related, need much more rigorous scientific definitions. They may include differences of opinion on definition, but these should be cited with verifiable and reliable scientific authorities.
- Parsa (talk) 18:14, 5 December 2008 (UTC)

Hatnote

Jheald re-added this see-also/other-uses below the disambig link:

The term heat has a precise meaning in thermodynamics, which is the subject of this article. For the looser idea of thermal energy, see that separate article.

I have reverted this for several reasons. Firstly, thermal energy is not a “looser idea” of heat. Second, I defined thermal energy in the disambig, thus make the above redundant. Third, I defined thermal energy in the lead paragraph to heat as well as added the said internal energy table that defines and contrasts heat in relation to thermal energy. Fourth, the phrase “heat has a precise meaning, which is the subject of this article” (obvisously). Fifth, it makes the article cluttered (one disambig is enough) and puts too much emphasis on the term heat, which as I have explained above is not a common term in published textbooks. Lastly, I know (from the entropy article) that Jheald has a tendency to add lengthy explanatory sentences (captions) below the disambig; but compared to other science articles this is not the Wiki-way. --Sadi Carnot 22:33, 5 July 2007 (UTC)

Sadi, I don't think you have looked at high-school general physics textbooks -- which is as much knowledge as many of our readers will have. It is important to tell those readers right at the top that this is not an article about what they might think it is -- namely heat in a general sense of thermal energy.

Having a link to a general disambiguation page is fine for readers who know they are looking for eg Heat (magazine) who will see immediately that this is not the article they are looking for. But such a dab does nothing to help readers, if they do not realise that this is not the article for the meaning they are looking for. If they do not realise that right at the top, they will simply get very very confused. That is why a specific hatnote is valuable. Jheald 23:06, 5 July 2007 (UTC)

Jheald, if thermal energy is used, discussed and clarified to a significant extent in the heat article, then why is the reader redirected twice over (the term is already in the disambig)? Furthermore, if you feel it is so important to clarify the confusion, then why don’t you write a new header paragraph in the heat article (header = “heat and thermal energy”, or “thermal energy”, or “thermal energy related to heat”, etc.)? --Sadi Carnot 23:14, 5 July 2007 (UTC)

Because a Lead should say what this article is about; not what it is not about. That is better achieved by the short 1-line hatnote. IMO this article should be about the concept of TdS, not the word heat. I think jamming both the narrow concept of TdS, and the broader concept of thermal energy into the same article serves our readers poorly. That is why I was against merging the two articles into one, and it was my impression that that was why other editors were also against merging the two concepts into one article. Jheald 23:21, 5 July 2007 (UTC)

Now that the history section is moved (history of heat, with a stubby here) and that the thermal energy has a stubby here (to clarify more than a hatnote can), then by all means go ahead and add more to the article about TdS; or are you making the suggestion that someone else do it? --Sadi Carnot 00:17, 6 July 2007 (UTC)

Sorry not to be clearer. As mentioned above, by TdS here I was meaning a shorthand for "the concept of heat as an amount of energy being transferred in opposition to heat as an amount of internal energy" (because that amount of energy will very often equal TdS); and not just the formula itself, or discussions of heat in terms of that formula -- my intention was wider than that. Sorry if this shorthand was confusing, and in retrospect probably ill-judged.

As to the hatnote, I still think that, because in introductory science teaching and in general discourse the word "heat" is widely used synonymously with thermal energy, it is better to dispose of this ambiguity before the article even begins. I think this is still advisable, even with a good paragraph just below the fold. If this is not the article people are looking for, it is better that they find that out straight away, before they even start reading. -- Jheald 08:16, 6 July 2007 (UTC)

Thermal energy (sub-header) in overview

How about we try it the way I have it now, with a clarifying paragraph in the overview. I think this will be more clear to new readers than a mis-defined (and conjested) hat note. Plus, I moved most of the history section to a new page: history of heat. --Sadi Carnot 00:06, 6 July 2007 (UTC)

I don't see any misdefinition in the hatnote; and I dispute that it makes the article congested. It merely clarifies, right from the off, that we are using the word "heat" in a specialist, more precise sense; rather than in the broader, more generalist sense that most readers may have mostly encountered it. Jheald 08:24, 6 July 2007 (UTC)

I don't see that there is really any more need for debate but I think you need to reconsider exactly how much of a distinction there is between your specialist versus generalist usage. I don't really see any except some examples of sloppy usage (these can be found for anything) and the generalist definition being less well defined. If we exclude those that should know better but are sloppy and focus on the those that have not thought about the precise definition of what they are thinking about the meaning approaches back to the well defined definition anyways. If something is at extremely high temperature and a layperson touches it but there is no heat transfer they will say that it is lacking heat. In fact if heat transfers up the temperature gradient they will say it is cold. These are not physically reasonable events of course but demonstrate what the layperson means by heat. There really is no need for any distinction between these usages. One is just less informed than the other but they both refer to the same thing. I think the article as it stands now does an excellent job of informing and letting the layperson understand the sensations that they feel and refer to as heat. I really don't think there is anything else to say about the generalist definition other than it is in some ways a figure of speech and is not well defined. The article already does that very well. --Nick Y. 17:52, 6 July 2007 (UTC)

From Wikipedia:Hatnotes: "most agree that they should be limited to the simplest possible form, preferably only linking to a standard Article (disambiguation) page". This is my perspective, and as I have stated above, the term "thermal energy" is found in less than 5% of science books, hence placing a double hatnote at the top of an article for a negligible term is unwarranted and puts overemphasis on a term that is generally not used. --Sadi Carnot 17:40, 7 July 2007 (UTC)

I think your statistics are looking at the wrong question. It's quite possible that "thermal energy" is a rare term in university-level books. Where it is not a rare term is in school physics, particularly for students first meeting the idea of different kinds of energy, and the conversion of energy from one kind to another (eg Key Stage 3 in the UK, i.e. 11-14 year olds). For typical KS3 material see eg these pages from the BBC. At this level, "thermal energy" is not a negligible term, it is an overwhelmingly common term.

Note also that at this level "heat energy" is used synonymously with "thermal energy". Many readers coming to Wikipedia may not have taken science at a level much beyond this (in fact probably a majority), and these usages will be their terms of reference, not anything more advanced. Wikipedia needs to be accessible for these readers too, not just readers who have taken the subject on further.

FWIW, note also the words that Sadi does not quote, in the rest of that sentence from WP:Hatnotes, "allowing slightly more extensive hatnotes when warranted in certain cases". Jheald 16:06, 10 July 2007 (UTC)

Again I think this conversation should end. There is consensus, albeit not unanimous. In the teaching of young children and even undergraduates there are often small white lies propagated for the sake of clarity. These usually involve ignoring complications and using terms loosely. --Nick Y. 18:44, 10 July 2007 (UTC)

Heat as energy in transfer or not, only really a semantic issue

Interesting discussion on heat only existing during transfer, which i think highlights a general point;

I think all words actually 'belong' to a human language, only being borrowed by physics, and as such are actually dynamic things, words can play happily with variable, illogical and even contradictory definitions. If you want to communicate without ambiguity and context sensitivity, then you have to use maths, that is what its for. To try and align an existing word with a newly defined concept, even if it is clearly better, is going to cause confusion in any educational context, and needs to be clearly explained as a different usage, over time new well defined, stable and generally useful definitions will tend to shine through, but you have to explain this with the current usage.

Think about the fact that the word 'Heat' existed before the equation that supposedly defines it?

Think about the problems this introduces with translation, where a word used for a thing will generally have different origins in a different language and so direct equality is only an approximation, you will then have to try and force words that are close in meaning in every language.

The term 'word Nazi', for me, in this context, carries a useful concept, and so the translation issue might be termed 'word imperialism', which carries equally insulting overtones.

But back on the definition of Heat, how about this; Feynman seemed to be happy that Heat exists as a static quantity, or did he just understand his audience?

Now although ice has a "rigid" crystalline form, its temperature can change-ice has heat. If we wish, we can change the amount of heat. What is the heat in the case of ice? The atoms are not standing still. They are jiggling and vibrating.

Feynman lectures on physics, chapter 1, lecture 1

for me the alternatives should just be pointed out and the usage being applied defined in each article, some less technical articles using Heat as internal energy, which then refers to a more advanced article, thermodynamics, that uses and clearly indicates it use as not commonly used. Asplace 19:51, 28 September 2007 (UTC)

I don't entirely disagree and the word nazi point is understood. Regarding Feynman, yes he understood his audience and no this statement does not indicate that he disagrees with the definition of heat. His point is that heat and internal energy are linked. Yes he is being sloppy in his terms but then again the choice of ice regarding heat and internal energy is being used to tear down the common misconception of heat. Yes, heat is occasionally used as a synonym of internal energy for educational simplicity. But atoms are also described as little balls that are linked together by bonds that are like little springs. Regarding the common usage of heat, as is discussed above, the common usage is actually most consistent with the technical usage of the term. "Turn the heat up." = Increase the internal energy flux in to the air within this room such that the temperature increases. "Could you please turn the heat down on the eggs." = Could you reduce the energy flux from the burner to the frying pan. "I can feel the heat of the sun beating down on my head." = I can sense the energy flux from the infrared radiation of the sun on my head. Verb form: "could you heat up the kettle please." = Could you increase the temperature of the water in the kettle by placing it on a heat source and causing energy flux into the water.--Nick Y. 17:26, 1 October 2007 (UTC)

sorry but i think your examples of common use are actually all about changing temperature, not energy flux. for example, any internal rearrangement, phase change, can produce a temperature change without any energy flux and people would clearly have no other label but 'heating' or 'cooling' for these changes.Asplace 22:26, 2 October 2007 (UTC)

I'm not going to engage in an extended argument about this but I will make a couple of points to help you understand my point. If you disagree so be it. Phase change requires work (energy flux, either as heat (see latent heat) or as mechanical work such as changing the volume of a thermally insulated closed vessel). Mechanical work is clearly not what is commonly spoken about in everyday parlance in regards to heat (except regarding the heat generated by mechanical friction). You say common use of heat is temperature. In order to increase the temperature there must be heat. In order to increase the temperature one must increase the heat. Yes, we are most interested in the temperature but even in our naive existence one of our most important concepts is that heat is necessary to achieve that goal. There is no magic temperature control we always control a heat device (something that causes energy flow) and we know it intuitively. If you are cold stand closer to the fire little caveman. Staying warm by wearing clothes is all about reducing heat flow out of our bodies through insulation, not magic. Heat capacity of objects we interact with is far more important to us the actual temperature. I would much rather be sitting on 50°C Styrofoam than 50°C steel, wouldn't you. There is a reason a heater is called a heater and not a temperaturer.--Nick Y. 23:46, 2 October 2007 (UTC)

this "Phase change requires work (energy flux, either as heat (see latent heat) or as mechanical work such as changing the volume of a thermally insulated closed vessel)." is just wrong, if i assume you are using heat to mean external energy flux, but strangely its ok if you use it to mean thermal energy. Phase change requires energy which can come from thermal energy and so you can have temperature change with no external energy flux, which is what i said, please double check before making further comment.

also, thermal energy and temperature are related in complex and material dependent ways, as you say, with is a actually a very good reason for having both.

here is a simpler restating of the issue;

heating IS the addition of heat.

heating is making something hotter. ( this is the crunch statement, which is no longer true with the thermo-dynamic definition of heat)

making something hotter is to raise its temperature

if the above are correct, then;

addition of heat MUST cause a rise in temperature. (rememeber this is not physics, its simply what the words mean in their common usage.)

and since the reverse is true, then;

temperature change IS heat change

example: say a gas in a closed system is condensing, it has not reached an equilibrium (without considering systems not at equilibrium you ignores basically all change), energy is liberated as the intermolecular forces draw the particles closer together, pressure drops but no external work is done, as long as the volume remains the same, and there is no reason it can't, so the energy released can only end up in the form for thermal energy, so the system gets hotter without any external energy flow. people would talk about this as the new heat having been supplied from some internal mechanisms. just like burning fuel and other chemical reactions.

and the point of the example is that its a case where temperature change is not the result of external energy flow and so also means external energy flow does not always result in a temperature change and so external energy flow is NOT heat (using the common definition), unless you try and persuade people that heating is not the same thing as making something hotter, which is not going to be easy, without a lot of confusion and BS. Asplace 22:13, 7 October 2007 (UTC)

• Yes, there are exothermic reactions etc. and nuclear reactions. I think you are getting to some very fine points that most lay people do not consider. Although I admit that there are certainly some cases where the lay person may indeed use heat and temperature change interchangably they are uncommon and can in most cases be corrected by defining appropiate boundry conditions. A fire is viewed as a heat source by the lay person and this is correct from a physics perspective too. Although the fire may not think about things in the same way since its temperature is raising due to an exothermic reaction occuring within its boundries of self idenitity. Psycologically we divide the world into two boxes for heat purposes, me and not me. We human beings are innately warm, when alive, due to exothermic reactions, yes, but this is usually assumed and not pondered on by the lay person. Even when thought about one might say that they have an internal heat source since our nerve endings for heat are on our surface and the bulk of the exothermic reactions are within us.

• Regarding your example: it is fundamentally flawed. Without heat flow or endo or exothemic reactions or nuclear reactions the average temperature will remain constant by definition. I think you may be tricking yourself into thinking otherwise. Even systems not in equilibrium have an average temperature. Yes energy may be absorbed by latent heat, but this requires heat to flow out of the system to reach an equilibrium point other than the one defined by the total energy in the system at the start. Since the average temperature of the system will not change I would say the observer (who can't feel anything by defintion of a closed system) would say there is no change. You might also be confusing yourself by how you define your boundry conditions. Perhaps the proper place to draw the boundry conditions is between the phases. If they are not in equilibrium then there will be heat flow between the phases and the temperature of the two boxes will change due to heat flow, but the total of the combined boxes will remain constant. Temperture is a measure of kinetic energy.--Nick Y. 15:29, 8 October 2007 (UTC)

please stop commenting, i tried but i can really not make a meaningful interpretation of all this, i can see parts of it that are simply wrong, parts that might be inconsistent if they meant anything, but mostly its just irrelevant to the point. Please do yourself a favour and check what you are saying, although from my experience this sort of stuff is consistently poorly understood.Asplace 17:56, 8 October 2007 (UTC)

• Although it is easy to confuse thermal energy and heat on first inspection and it is even easier to confuse the lay understanding of them (two potentially confused parties), on deeper inspection and a full understanding of both the physical nature of heat and temperature and the lay usage of the terms it becomes ever more clear that at least the majority of the time the lay usage is consistent with the physical usage to a surprising degree. End of discussion, at least for me. (Willing to help if asked however)--Nick Y. 18:28, 8 October 2007 (UTC)

OK, but reassigning the term 'heat' to a new definition, in such a way that;

"heating" and "getting hotter" are now disconnected, is going to be the source of huge confusion. Asplace

They are not disconnected. Heating is a primary means of getting hotter.--Nick Y. 21:57, 9 October 2007 (UTC)

so you do see that the term heating (as used in the article) is not the sole way ( a-priori) for something to get hotter?

or in other words;

something getting hotter by some internal mechanism is not regarded as it being heated.

Asplace 15:15, 10 October 2007 (UTC)

Yes, this is common in thermally insulated chemical reactions as in calorimetry. The internal spontaneous generation of thermal energy can result from chemical and nuclear reactions without heat. I would not say that nuclear reactions are common experience shared by the vast majority of the public nor are they easily thermally insulated. When chemical reactions occur (and they are ongoing all of the time) they are not thermally insulated and therefore the benefit or experience of the reactions (our interaction with them) are as a heat source. We think of a fire as a heat source because the benefit to us is the heat flow. To thermally insulate a fire negates the benefit but yes there is no heat. I.e. We care about the heat of the fire not the temperature or the change in temperature. If we can not extract the heat then it is useless. Chemistry can certainly be used to challenge our naive assumptions about our innate conception of heat but is far from commonplace and the result of this challenge is and has been a refinement of our established conception of heat as having a source and a sink. Heat flows from the fire into my body. If it does not flow I feel no heat regardless of the temperature differential. I hope this is helping you.--Nick Y. 17:14, 10 October 2007 (UTC)

try another example:

earth irradiated by the sun, light has to be work in the first law, earth in a vacuum, so earth is not 'heated' by the sun!!

FYI 1. you can sample the temperature of an object without effecting it, by using a probe at the same temperature and noting the lack of energy exchange, you seem to be confusing this with quantum mechanics somehow.

2. In TD there is no distinction between the sources of non thermal internal energy, so no point in talking individually about chemical,nuclear?,phase change,crystallisation etc etc.

3. You seem to be stuck in thinking this is a conceptual problem, it isn't, its about assigning an existing word to a concept which has significant differences from existing usage, I've checked the Feynmann lectures and an old university thermodynamics text book ( F. mandl ) i had lying around and the usage of the term is definitely counter to that used in this article. I and these sources are not suffering from conceptual problems. Asplace 19:58, 10 October 2007 (UTC)

I do not see how I can be of any greater help to you on the issues you raise except to say: The use of heat in inexact ways as an educational tool has been discussed above and these specific examples are not how the word is used in common parlance for that matter. Measuring temperature and *feeling* heat are separate issues. Yes you can measure temperature in a thermally insulated system but you certainly can not feel heat flow or measure any for that matter since it is thermally insulated and thus=0. I'm sorry I can not be of more help in furthering your understanding. I would encourage you to be open minded and study this subject further on your own. --Nick Y. 22:01, 10 October 2007 (UTC)

P.S. Regarding your example I would encourage you to read the section in this article on radiation. It is all explained there.--Nick Y. 22:04, 10 October 2007 (UTC)

woops, i changed from a laser heating an object in a vacuum, to the more dramatic sun/earth and forgot the radiation would not be coherent, so i should of said;

example

an object in a vacuum is irradiated by a laser, the energy in the light has to be work, not q, in the first law, so by this articles definition of 'heat' the object is not being 'heated', but clearly it gets hot!! this is not what the word 'heat' means, and i have previously given multiple very well regarded and verifiable sources that show this clearly, so as i understand it as a good wikipedian i have a responsibility to start correcting this article. Asplace 18:55, 11 October 2007 (UTC)

BTW, wiktionary has 'heat' as thermal energy, and so does the article called sensible energy? i guess if you looked, the 'thermal energy' definition of heat would be in hundreds of articles, many of which might be linking to this article, which then uses a different one, confusing or what? —Preceding unsigned comment added by Asplace (talk • contribs) 19:10, 11 October 2007 (UTC)

I would encourage you to not be bold in regards to your position and start editing your misunderstandings into the article. The consensus is the opposite. Simply because errors are made elsewhere does not mean that they should be repeated here. Your new example shows that you are thinking hard to challenge the definition of heat. This example, however, has been thought about many times by many people over many years. This is simply an example of non-spontaneous radiative heat transfer. Yes, work is being done, as you identify, but what the work is doing is causing heat to flow in a non-spontaneous direction, like a heat pump and without a medium of transfer. A seemingly perplexing example for the layman, nonetheless it is heat. This example might make a good example/section of the article if you were inclined. I would even help, but not to propagate misunderstanding or confusion but to enlighten.--Nick Y. 19:38, 11 October 2007 (UTC)

i think your physics is wrong, the energy source can not have a defined temperature, (the rate of heating of the object is not dependent of the temperature of the laser, in any sense, it can continue to get hotter indefinitely, so no thermal equilibrium), and without temperature defined at both source and sink you are not talking about heat flow, in this case the energy flows as work, this is not a problem of physics, it simply means, as with the previous examples, temperature change with no heat flow, ( or heat flow with no temperature change) either of which breaks a fundamental concept associated with the word 'heat', the article missing inconvenient truths like this makes it more of a point-of-view crusade than impartially informative.Asplace 00:00, 13 October 2007 (UTC)

I stand by my statements. You are confused about certain subtleties. Lasers require continuous pumping in order to continue functioning which means the lasing medium is not a closed system. The temperature of the target will change while the laser remains in constant dynamic equilibrium because it is being pumped (energy in=energy out, for the laser). I.e. the laser medium is not the ultimate source but only a means of packaging. There is energy flux (heat) out of the laser to the target but the other side of lasing medium there is an arc lamp or something with inward flux (running on 120V AC power). Again it is a failure to understand and define boundary conditions that is confusing you.--Nick Y. 19:41, 16 October 2007 (UTC)

obviously i was considering a closed system, one that included the lasers power supply, in a non-thermal form, battery, etc. thermodynamics still applies to a system like this. i think you are unclear about systems in general and are then choosing the system boundaries in order to allow enough intentional leeway to be able to fit what you want to see.Asplace 15:47, 17 October 2007 (UTC)

Then it should be clear that the laser has a power source and is a heat source and that the temperature of the target is increased by radiative heat transfer from a source of constant temperature in a perhaps non-spontaneous direction through the application of work derived from the power source. I will leave it there. I can be of no more help.--Nick Y. 17:08, 17 October 2007 (UTC)

sorry, but being wrong can never be clear, please do leave it!Asplace 16:04, 18 October 2007 (UTC)

heat as 'net' transfer only

i think you need some reference to heat being only applicable to the NET transfer of thermal energy, in that, when two objects are in TDE and equal amounts of thermal energy are flowing in either direction, then no 'heat' is considered to be flowing, since dS is zero, but that with the removal of one of the two energy flows, the other energy flow although not ostensibly changing would need to be relabeled from thermal energy to 'heat'. This would emphasis that this definition of heat can not generally be broken down into subsystems, as might be assumed if casually compared to energy or force, but is a property of a complete dynamic system. —Preceding unsigned comment added by 82.27.224.69 (talk) 16:31, 13 October 2007 (UTC)

These issues could probably be better explained to the lay person but perhaps the article on flux is the better place to understand the fundamentals of flux. Although it is best to explain as much within each article sometimes referring back to more fundamental articles is best. We can't explain vector mathematics here either nor differentials, both of which are needed to rigorously describe heat.--Nick Y. 19:47, 16 October 2007 (UTC)

units

Names of units called after persons must start with lowercase: joule and watt (abbreviation is uppercase: J and W). --Virginia fried chicken (talk) 12:20, 25 November 2007 (UTC)

I changed this --Virginia fried chicken (talk) 15:25, 26 November 2007 (UTC)

Definition of heat and temperature

There is much confusion in this article, most of which arises because there is no satisfactory defintion of temperature. The two are intimately linked by the Boltzmann constant. Defining heat (Q) as "any transfer of energy" as does the opening statement is a contradiction, a transfer of heat would be a change δQ, a change of energy would be δE. According to this definition, what then is Q if it isn't the form of energy called heat?

The origin of modern "heat science" (thermodynamics) was the realisation that heat was not a substance (caloric or phlogiston) but the kinetic energy of some sort of fundamental particles that were free to move, i.e to vibrate in a fixed location for a solid and move freely as for a gas, there being an intermediate liquid phase for many materials. The reality of this was establisbed by Einstein with his explaination of Brownian motion which gave conclusive mechanical evidence for Dalton's atomic theory. Subsequent work showed that composite, none spherical particle (now called molecules) had other degrees of freedom that contained energy, thus their total energy, at a given temperature, was greater than the fundamental particles. (Fundamental paricles are only approximated by monatomic gases.)

The conclusion is; heat is that energy contained in the motion of fundamental particles, particles whose mass is unspecified but can only have motion in three (translational) degrees of freedom. This definition of heat does not exclude particles with more than three degrees of freedom, but the definition (and the reality!) of temperature takes into account the translational degrees of freedom only. There is a good reason for this, translational movements are the only way fundamental particles can exchange miroscopic mechanical energy, which explains why temperature is such an important property in thermodynamics.

There is a problem of usage which causes many difficulties and much confusion, because the translational and other motions of molecules are intimately linked, the heat of a system of particles is given as the total energy of the particles, change the translational motions (i.e. change the temperature) and you assuredly change the vibrational energy. The clue here is the various specific heats, materials with different specific heats are pressed into the same definition of temperature when it comes to exchanging energy through collisions.

It interesting to note that this is a purely mechanical definition --Damorbel (talk) 13:52, 16 January 2009 (UTC)

WTF?

When I first loaded this page, there was about three paragraphs of Arabic text in the beginning of the article. After refreshing, everything was normal. Was there some kind of vandalism that was quickly fixed or something? —Preceding unsigned comment added by 68.228.166.58 (talk) 19:38, 1 November 2009 (UTC)

I have a question

what is the differance between heat and tempature? —Preceding unsigned comment added by Lorifalcon (talk • contribs) 02:15, 6 November 2009 (UTC)

Heat is a flow of energy. Temperature is a measure of energy content.--Nick Y. (talk) 15:34, 6 November 2009 (UTC)

And heat capacity then? What is your definition of heat capacity (specific heat).--Damorbel (talk) 22:29, 6 November 2009 (UTC)

You must be joking

This new revision [1] really makes a laughing stock of the whole article, it reference the First law of thermodynamics which completely contradicts it! For example "The first law of thermodynamics states that the energy of a closed system is conserved". No it doesn't, the first law article "states that energy can be transformed (changed from one form to another), but cannot be created or destroyed." The "First law" article recognises that in the course of energy transformations these tranformations can result in equilibrium conditions, typically chemical transformations do not go to completion but result in an incomplete state but the total energy involved does not change.

More rubbish "In physics and thermodynamics, heat is the process of energy transfer from one body or system due to thermal contact, which in turn is defined as an energy transfer to a body in any other way than due to work performed on the body" Oh really? What about chemical reactions, combustion etc.?

From the changes you have made I suspect that you do not have the necessary knowledge to edit this already deeply flawed article. If you really want to making changes you should first consult on the discussion page. --Damorbel (talk) 08:20, 13 November 2009 (UTC)