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I'm not saying I'm an expert, and I'm not here trying to squash free thought or expression, but my substantial background in thermodynamics provides me some perspective in the supposed field of this article. My perspective is that while I have seen one US High school text present a concept of "thermal energy" when teaching elementary concepts of kinetic theory of ideal gases, and I offer no opinion as to the doubtful pedagogical merits of such use, and I may possibly have used this term inappropriately at a cocktail party once, and if so I'm truly sorry, yet beyond that I am not aware of scientific authority which articulates or advocates the generalizations and definitions offered in this article. Thermodynamics is generally regarded by Physicists and Chemists as falling into the philosophical realm of a "science" which concerns itself with HEAT, with WORK, with TEMPERATURE and ENTROPY, with PRESSURE and VOLUME, it conventionally defines ENTHALPY (H), GIBBS FREE ENERGY (G), HELMHOLTZ ENERGY (F), and INTERNAL ENERGY (E) but nowhere do I find anywhere, including the Britannica article cited, an authoritative exposition or definition of "THERMAL ENERGY". The author may have (incorrectly) confabulated with INTERNAL ENERGY which, for an ideal gas has the properties s/he states, but for no real substance. I am aware of several prior editing wars related to this "thermal energy" concept in other articles, and have seen it persistently inserted into fundamental definitions in the Wikipedia. I've made no modifications here and I'm NOT starting an editing war here, but my technical opinion is this article should provide other authoritative references (which I doubt can be found), or should be greatly revised and reviewed by a technical expert having a PhD in the field or by a PhD teaching upper division thermodynamics in Physics, Chemistry, or Engineering. —Preceding unsigned comment added by 76.191.132.120 ( talk) 00:55, 23 January 2008 (UTC)
So the difference between kinetic energy on a atomic/subatomic/elementary/quantum level and thermal energy is.....?
The Description section is inaccurate in many ways:
It should be rewritten. Warning added to article. -- Tromer 01:27, 16 October 2005 (UTC)
It appears that this is mostly a web page about thermal energy phrased entirely in neologisms, using newly invented English terms instead of the traditional Greek and Latin; indeed there's a change comment on the Thermal energy page saying, "moved Thermal energy to Warmal inwork: English term instaed of Greek", although I can't find earlier versions of the thermal energy page in the history. As such it's amusing to read, and it seems at least mostly correct, but it would probably be more useful if phrased in the traditional words, so that its readers could communicate with people using the traditional terms. Kragen Sitaker 02:08, 22 December 2005 (UTC)
The Description section is not just inaccurate, it is absolutely awful. It should be rewritten completely. Thermal energy is NOT quantified by temperature; "infrared radiation often linked to thermal energy" is a very vague phrase; the discussion of oscillators and their relation to thermal energy is unclear; the second law of thermodynamics is stated in a very curious and not very useful form ("thermal energy is special among the types of energy" is unphysical and vague, and "heat is a form of energy of lower quality" is completely meaningless). In short, this section needs to be completely rewritten, preferably by a physicist. 131.111.8.96 05:13, 3 January 2006 (UTC)
Thermal energy is not heat. It is the energy of the particles in an object. The temperature of an object is just the average amount of energy per particle but thermal energy is the total amount of energy in something.
MYT 03:52, 23 February 2006 (UTC)
I've fixed some of the errors in the article. With part about the laws of thermodynamics, I just cut that out completely and added a link to its main article at the end. They are really not necessary and not that relevant to the subject. I could say that about much of the rest too. Well, the thing's better than before, and that's all that I claim. -- myncknm 05:47, 11 March 2006 (UTC)
Hmm, the page seems to have been blanked and restarted. Good? I think it was. There was a lot of irrelevancy and badness in there before. -- myncknm 01:41, 24 May 2006 (UTC)
I have looked at many topics about thermal energy and have found no definition. It is energy caused by heat —The preceding unsigned comment was added by Axiomwheeler ( talk • contribs) 04:07, 12 February 2007 (UTC).
I completely rewrote and condensed this (also removed the picture that had little to do with 'thermal energy'); the old version was poorly written and quite redundant. If anyone wants to expand it, they should start from my text. The way, the truth, and the light 07:50, 6 June 2007 (UTC)
The first line of this page begins, 'Thermal energy or thermodynamic energy, often called heat...'. Shouldn't 'thermal energy' and 'heat' have the same page, then? I am not a physicist, but based on my understanding I don't see the need for separate articles on these subjects. Since heat is a far higher quality article than this one, I suggest merging 'thermal energy' into that page. Terraxos 05:51, 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 20:42, 18 June 2007 (UTC)
This page should be deleted rather than merged- I can't see any new material here. Thermal energy has a meaning but not one that is different from internal energy (I don't know what whoever wrote this thinks is the internal energy of an object at absolute zero). Heat transfer is the mechanism of energy transfer between objects of different temperatures. Most of this article is about heat transfer, not thermal energy. MAG1 22:34, 18 June 2007 (UTC)
I think we should keep these pages separate. I'll try to elucidate the differences when I have a chance in a couple weeks. In the meantime I think there should be no deletions or mergers. Scott.medling 22:49, 24 June 2007 (UTC)
I think the three should be merged, as the differences are subtle enough to explain all in the same place. This is the way they are introduced in textbooks, too. See Talk:Heat#Merger_with_Thermal_energy. — Omegatron 23:44, 24 June 2007 (UTC)
I realize this is an oudated discussion, but I need to point out something for the benefit of anyone reviewing it. Thermal energy and internal energy are not the same thing. Thermal energy is defined as energy from molecular motion, whereas internal energy is all the energy inside a system and thus also includes chemical bond energy and so on (ie ). Having said that, here's where the confusion arises. Some disciplines might omit from their definitions those components of internal energy which are not relevant to them. This is because when we work with internal energy, we're only interested in how it changed (or could change). Any component which does not change will not affect our calculations and can essentially be ignored. For example, mechanical engineers and non-nuclear physicists can totally ignore the chemcial and nuclear energy in their systems. This energy will never be accessible to them so it is as if it is not even there. (This may be why some in this discussion have argued that ; if their only training is in mechanics, then they may not have seen it defined any other way!) But a chemist knows there's also chemical energy inside a system. And a nuclear physicist knows that there's nuclear energy in it. Since Wikipedia is for all disciplines, we need to keep in mind that internal energy actually includes much more than just thermal energy. Riick ( talk) 16:28, 23 August 2010 (UTC)
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) people if you don't know what thermal energy is don't ask me —Preceding unsigned comment added by 204.2.37.50 ( talk) 21:08, 30 January 2008 (UTC)
why they call thermal energy for energy of heat an —Preceding unsigned comment added by 76.30.143.169 ( talk) 14:42, 25 October 2008 (UTC)
Thermal Energy:1 bottle Litter,a large ballon,a bowl of hot water[not boling],a bowl of ice cold water,and a small rock.p.s this is materials that you need for a science project!
Bold textTHE BEST!!!!!!!!! —Preceding unsigned comment added by 76.108.50.244 ( talk) 01:43, 20 March 2009 (UTC)
This is a crapppppppppy web come onnnn wat info u give???????? NOTHING NOTHING and more NOTHING U cant even tell me wat heat energy is!!!!!!!!!! —Preceding unsigned comment added by 41.242.191.163 ( talk) 19:42, 21 July 2009 (UTC)
Although this has been discussed before without coming to a clear conclusion, I propose merging this page with Internal energy. Specifically, all that needs to be said about this topic is already said in Internal energy#Composition, where, compared to this article, it's said much more clearly and without the added nonsense. Djr32 ( talk) 19:40, 5 October 2009 (UTC)
The article was rewritten and reinstituted on 2010-11-03T23:06:30 by User:Kbrose.
I'm a Physics teacher and I'd like to share my opinion on the definition of thermal energy. First of all, thermal energy and heat are not the same. And I'm glad this article shows this difference perfectly. Thermal energy is a component of internal energy whereas heat is a form of energy transfer (the other forms are work and mass transfer). Now, some people consider thermal energy only to be the quantity of kinetic energy of all the molecules, atoms, electrons, etc. of a system. I do not like this definition because it does no consider what happens when a system absorbs or release (internal) energy while changing from a state to another. For example, consider what happens when a piece of ice starts abosorbing energy, initially its tempeature increases and, therefore, it means that its internal energy has increased, specifically its thermal energy (becauses its internal kinetic energy increased). If the piece of ice keeps absorbing energy, eventually it will not increase its temperature for a while but will change its state from solid to liguid. The question is: WHAT COMPONENT OF THE INTERNAL ENERGY INCREASED DURING THIS STATE CHANGE? The nuclear energy? Nop! Because nothing happened at the nuclear level. The chemical energy? Nop! Because no chemical bonds have been created or destroyed. When the state changes, it means that the spatial arrangement of the molecules of the system changed. So, what component of the internal energy accounts for this? I say, necessarily, the thermal energy but if it is defined to consider ONLY the internal kinetic energy it WILL NOT BE USEFUL to answer this key question, but, if it is defined to consider ALSO the state of the system, then, that energy absorbed by the piece of ice to change its state will represent an increment in the thermal energy. When I teach my classes I teach that thermal energy has two components:
Sensible energy: The internal kinetic energy of the system and,
Latent energy: The potential energy associated to the state (solid, liquid, gas, plasma, etc.) of the system.
In my classes, sensible energy and sensible heat are not the same. Sensible heat is defined as the amount of heat (the quatity of energy that must be absorbed or released) necessary to produce a change in temperature. Besides, latent energy and latent heat are not the same either. Latent heat is the amount of heat (the quatity of energy that must be absorbed or released) necessary to produece a change of state.
So, by using "my" definition, the problem is solved. Pitifully, this definition is not widely used. An example of this case is this article. Here, thermal energy only considers the internal kinetic energy but not the potential energy relative to the state of the system. There's a couple of websites that share my point of view:
http://www.ifpaenergyconference.com/Thermal-Energy.html http://wiki.answers.com/Q/Does_thermal_energy_increase_during_a_phase_change
George Rodney Maruri Game ( talk) 03:03, 19 November 2010 (UTC)
Oh, I'm so glad for your words. You have said many things which are completely true. First of all the sources are not "that" reliable. I understand that and besides the first constradicts itself. Obviously for me it's been really hard to find good sources. Thanks for answering "my question" (potential energy) in fact, it's all about terms. Potential energy is the energy associated to the spatial arrangement or configuration of the components and, as you might have noticed, I define latent energy as "the potential energy associated to the state (solid, liquid, gas, plasma, etc.) of the system." It means we share our point of view only with different terms. In short, LATENT ENERGY IS POTENTIAL ENERGY. The other question is "Should we consider latent energy (potential energy) as a part of thermal energy?". If we say "yes"... let's see... if temperature only has to do the average "kinetic component", it is, the sensible energy (not heat, remember "my" definition?, he, he), it means that temperature wouldn't be related to the average of the total thermal energy but only to one component. But if the answer is "no", temperature would give a reading of the average of all the "thermal energy". Thank you for answering. I hope some day all this matter finally ends up with a world-wide agreement regardless of the terms but with the same "idea". George Rodney Maruri Game ( talk) 16:41, 30 November 2010 (UTC)
Again, thanks for your comments. To be honest, reading your words enhance my own learning about this topic. I agree with you practically in everything. But I have this "maniatic" custom of "labeling" every little thing. So, what do you think of these (obviusly as you have stated some of my ideas are unsupported but I want to know your opinion):
Chemical (potential) energy: The potential energy associated to the intra-molecular (inter-atomic) configuration of a substance.
???? (potential) energy: The potential energy associated to the inter-molecular configuration (lattice). May I suggest ???? = "latent" (I know there are no supportive sources, but just tell me your opinion about the idea, I´ve come to acknowledge your great insight about all this)
Thermal energy: Total kinetic energy at both inter-molecular and inter-atomic levels of a sample of substance.
Sensible energy: Average kinetic energy at both inter-molecular and inter-atomic levels.
Temperature: A "measure" of the average kinetic energy (sensible energy) at both inter and inter-atomic levels.
Latent heat: Energy necessary to produce a state change.
Sensible heat: Energy necessary to produce a temperature change.
I appreciate so much to have the opportunity to share my ideas with someone who, in my opinion, has unselfishly brought a great level of comprehension relative to this topic (at least for me because I´m still learning, too young to look like a Physics teacher, he, he, he). I understand that even if you agree on my "ideas" they won´t make it into the article due to lack of reliable, published and widely accepted sources.
George Rodney Maruri Game (
talk)
18:49, 3 December 2010 (UTC)
Simply wonderful and precise! Finally I think I've come to understand all this "almost perfectly", because I still have a couple of questions, though. Thank you so much for your patience. One question is: Is temperature an exact reading of the average kinetic energy of a sample or just a "measure"? That way there wouldn't be no need for two terms (what I proposed as sensible energy would be the same as temperature: The average kinetic energy at the inter-molecualar and inter-atomic levels). The other questions is (or rather request): Would it be possible that this explanation you have given (and further ones you might give in the future) to me can make it into this article, please? I mean if it has been so valuable to me, maybe others can get some benefit also. You know, it is true that I teach Physics but just at the high school level and I bet you have studied a lot more than me, probably you teach at a college or university or your work requires you to understand all this very well. Nevertheless, I think that all this confusion remains because all this thing is not taught earlier and correctly (at high school!). That way colleges or universities teachers wouldn't have to "destroy" so many myths (fix misconceptions) about internal energy, thermal energy, heat and temperature. Thank you again. I hope I'm not taking so much of your time. George Rodney Maruri Game ( talk) 16:43, 5 December 2010 (UTC)
What can I say but thank you. Now, doubts are just memories! I think I will come here to the talk page every time I need to look for information on this topic, he, he. See you around... George Rodney Maruri Game ( talk) 02:36, 7 December 2010 (UTC)
The article says: In the microscopical description of statistical physics, the thermal energy is identified with the mechanical kinetic energy of the constituent particles or other forms of kinetic energy associated with quantum-mechanical microstates.
The distinguishing difference between the terms kinetic energy and thermal energy is that thermal energy is the mean energy of disordered, i.e. random, motion of the particles or the oscillations in the system. The conversion of energy of ordered motion to thermal energy results from collisions.[5]
The reference is not online, but if it actually says this, it is wrong. The thermal energy in an ideal gas is all kinetic energy, but the thermal energy of solids is (on average) twice as much as for gases at the same temperature. This is a simple demonstration that since twice the heat is stored at the same temp in a solid as in a monatomic gas, and since temperature is connnected to mean kinetic energy of atoms, that therefore the extra 100% of energy-content (thermal energy) stored in solids as you raise their temperature, is not kinetic energy, but some other sort of energy (in fact, it is the potential energy component of vibration). So all this is wrong.
Incidentally, some texts (not all) go even further to define "latent heat content" as part of the thermal energy. This makes perfect sense, as latent energy contributes to energy that is absorbed and extracted from systems during heat transfer and stored in the system in the meantime as a thermally accessable reservoir of energy (like any degree of freedom). What else would you call latent heat content, if it participates fully in heat storage, except system thermal energy?
Of course, this makes hash of the "contributes to temperature" definition of thermal energy (unless qualified as being in a single phase), but that definition is not written in stone. A better one is that thermal energy (what used to be called heat content) is that part of internal energy which changes when you add or subtract heat, using a temperature gradient. Very simple. It isn't exactly classical heat capacity times temperature, unless you add a term covering heat absorption due to phase change (where heat capacity is infinite). But phase changes add to the thermal energy ("heat content" in the old terminology) of systems, as anybody using steam condensation to extract heat can tell you. Steam has a thermal energy that the equivalent amount of water at the same temperature, does not. Any engineer would regard it that way. S B H arris 19:47, 6 April 2012 (UTC)
I must fix the thermal energy article, which states that thermal energy is a state function. Nonsense! Except in the limit that no chemical or PV work is done, so that a change in thermal energy becomes a change in internal energy, which is a state function. Otherwise the difference between constant pressure and constant volume heat capacities (which are different for every substance, even if good approximations) show clearly that temperature is path-dependent, and thus so is thermal energy or "heat content." You can get an object to the same temperature in two ways (for example), using two different total amounts of heat dumped into it, if you let it do PV work to get to the state in one case, but not in the other. So δW = 0 and no change in chemical potential and so on, must be specified before we talk of thermal energy in any such fashion. And then indeed, "thermal energy" (an idealized quantity in the limit of no other energies that are reversibly turned into heat at the same time) is that component of internal energy that can be extracted by a temperature gradient. But if you don't make δW = 0, you can, by fiddling with work or other internal heat/chemical potential sources, extract any number of differert amounts of thermal energies from the same object, in passing to a given lower temperature (or to absolute zero, for that matter). If you do so, that makes thermal energy content inherrently ridiculous. S B H arris 01:47, 2 June 2012 (UTC)
The article opens with:
Thermal energy is the part of the total internal energy of a thermodynamic system or sample of matter that results in the system temperature.[1] This quantity may be difficult to determine or even meaningless unless the system has attained its temperature only through heating, and not been subjected to work input or output, or any other energy-changing processes.
Which is not correct.
Thermal energy is that energy in a system due to the (total) kinetic, i.e. including rotational energy, of the particles of the system.
Since there is no requirement for the system to be in equilibrium to 'have thermal energy' then no 'system' temperature can (or needs to) be identified, the thermal energy in a system is merely the sum of the kinetc energy of the particles in the system.
P.S. I notice that the 1st ref. in the article is to an article in Encyclopedia Britannica which of course derives some of its material from Wikipedia. Wikipedia is, of course, not a reliable source. -- Damorbel ( talk) 08:14, 5 November 2012 (UTC)
"For the tenth time half of thermal.... What is your point? In solids the thermal energy is stored in the vibrations of the various bonds making the system a solid. Since these are vibrations the energy is, according to the period of the vibrations, regularly exchanged between kinetic and potential energy and, omitting the tranfer that takes place in non-equlibrium conditions, all the potential energy is changed into kinetic energy, thus they are equal. So the total energy is equal to the maximum potential energy or the maximum kinetic energy or half the potential energy plus half the kinetic energy. If you wish to go further in this matter you may wish to study phonon interactions wherby the nature these vibrational energy processes are given a sound theoretical basis, including thermal conduction. -- Damorbel ( talk) 10:05, 5 November 2012 (UTC)
I have removed the text :-
In engineering and technology, and particularly in fields that deal with civil energy use and conservation in building construction, heating systems, and power generation, heat and thermal energy are often indiscriminately used interchangeably.
from the section: http://en.wikipedia.org/?title=Thermal_energy&oldid=523879256#Distinction_of_thermal_energy_and_heat
Which is preposterous twaddle. I am sure there is no reliable source for this assertion. -- Damorbel ( talk) 13:42, 21 November 2012 (UTC)
Where does this come from? :-
According to the zeroth law of thermodynamics, heat is exchanged between thermodynamic systems in thermal contact only if their temperatures are different,
Surely the second law! (And it should be energy that is exchanged.) -- Damorbel ( talk) 14:07, 21 November 2012 (UTC)
The article has the following in the intoduction:-
Thermal energy is the part of the total internal energy of a thermodynamic system or sample of matter that results in the system temperature.[1]
Which is not at all true. Thermal energy is the energy of particles in motion, it can be linear motion, rotary motion or vibratory motion. The particles do not need to be part of a defined system, not even excepted by the needs of an inertial system.
Worse still there is no direct connection between system temperature and thermal energy. This latter has a refernce to the Encyclopedia Britannica which often uses Wikipedia as a source, what a joke! BTW, anybody know what System temperature is supposed to mean? -- Damorbel ( talk) 15:50, 21 November 2012 (UTC)
I have revised the opening statement according to the above discussion. Of particlar importance is the removal of the link to the Encyclopedia Britannica which appears to have copied its content from a previous version of Wikipedia! -- Damorbel ( talk) 06:35, 21 February 2013 (UTC)
It is obvious nonsense to suggest that putting an object in uniform translatory motion affects its "thermal energy", which is what the last version of the article implied. Thermal energy cannot simply be the average kinetic energy of particles, because "thermal" implies a thermal distribution, and (for example) uniform motion gives every particle the same kinetic energy - which has nothing to do with thermal anything. The real problem is that "thermal energy" doesn't make much sense, and this article should be entirely re-written to reflect that. Waleswatcher (talk) 22:14, 24 February 2013 (UTC)
Bulk particle motion in one direction is not thermal energy. A perfect crystal at 0 K moving half the speed of light, has a hell of a lot of kinetic energy. But it still has no thermal energy, and it still has a temperature of zero. It has the same temperature in all frames, in fact, which is zero. S B H arris 22:36, 25 February 2013 (UTC)
You don't HAVE an argument. It doesn't matter if a meteoroid produces a great deal of heat when it strikes the atmosphere or the earth (or whichever). The point is that its kinetic energy of motion does not make it hot BEFORE it strikes and produces friction. It can (and usually is) moving very fast but is still very cold. This high kinetic energy is not "temperature" or "thermal energy" in space. It is only converted to thermal energy and heat that raises temperature, after it hits. S B H arris 23:23, 27 February 2013 (UTC)
It doesn't apply to temperatures when they are zero, since zero multiplied by any number is zero. An object with a temp of zero in any frame , will have a temp of zero in ALL frames. Of course, that's not true of kinetic energy. Which is why this type of frame- dependent KE doesn't add to temperature.
If you think you can give an object at rest at 0 K a temperature by moving it (or yourself), do you think it will then start to give off thermal IR radiation? Do you think it radiates energy away like this in some frames but not at all in its rest frame? Very funny. S B H arris 18:25, 5 March 2013 (UTC)
Indeed. You have just made a good argument for why the idea of the temperature of a single particle is meaningless. S B H arris 20:25, 6 March 2013 (UTC)
You are the person who asserted that one particle could be said to have a temperature, were you not? Well, it can't. S B H arris 21:55, 6 March 2013 (UTC)
Currently the opening section of this article has:-
In what sense is "potential energy" thermal, i.e. a function of temperature? For example, how can gravitational potential energy be thermal and how can chemical potential energy be thermal.
These are serious inaccuracies not appropriate to Wikipedia. -- Damorbel ( talk) 06:30, 24 May 2013 (UTC)
Further. The following text also appears :-
Thermal energy does not need to be conserved or even strictly upheld to be an important property. Exactly the same can be said for chemical and other forms of potential energy. These are all part of physics, the explanation of observational science. The fact that some quantities are conserved and others not are laws that provide understanding of how physical processes operate in a logical way.
This whole section needs revising to remove the confusion between kinetic and potential energy. -- Damorbel ( talk) 07:21, 24 May 2013 (UTC)
Here is one particular thermal system that has no potential energy. Therefore potential energy can never be thermalised
Um, no, Jheald; I did not say anything like:-
To expand what I said just a little, "gas molecules under pressure in a container do not have potential energy due to intermolecular forces as do the molecules in liquids and solids." To be more explicit the presence (or absence!) of potential energy (in any form) has no influence on temperature , that is why water boils at a constant temperature, freezes at a constant temperature etc., etc. -- Damorbel ( talk) 06:52, 29 May 2013 (UTC)
Can't the thermal energy of a system be defined as as state function something like the following?
Of course, by "in principle", I mean I'm allowing for the hypothetical process mentioned in the definition to take place (arbitrarily close to) remaining at equilibrium and to take the temperature of the system (arbitrarily close) to absolute zero, where the thermal energy becomes zero. Doesn't this definition constitute a state function, i.e. its value doeesn't depend on how the system got into that state, correct? It is an operational definition in that you can measure this quantity of energy to some precision by cooling the system in a certain way. If this definition isn't consistent with the concept of thermal energy, when and why do they differ?
DavRosen ( talk) 05:54, 21 July 2013 (UTC)
It might be helpful to recognize that there are of course numerous interconversions between forms of energy and that only TOTAL energy of the UNIVERSE is conserved. An "isolated" system is a reasonable facsimile. Given this it might be worth questioning the tendency to single out thermal energy as particularly ill-defined because of the fact of energy interconversion. The same can be said of all forms of energy except for total energy of the universe or isolated system. Thermal energy is simply an especially good example of a form of energy with many interconversions both input and output. Davidr222 ( talk) 16:15, 12 June 2014 (UTC)
The term 'Thermal energy' is a not used in thermodynamics. It has no precise definition so it can mean different things in different contexts. This means that it should not have its own Wikipedia page. In my view an article on 'Thermal Energy' should redirect to Internal energy and Heat.
The article incorrectly states:
1. "Thermal energy is the part of the total potential energy and kinetic energy of an object or sample of matter that results in the system temperature." Potential energies and non-translational kinetic energies of molecules do not contribute to the temperature of a substance.
2. "It is represented by the variable Q, and can be measured in joules." Q is a defined term in thermodynamics. In a thermodynamic process, Q represents heat flow, which is essentially energy transferred to or from a system by means other than mechanical work ie.: The First Law of Thermodynamics: Q + W = ΔU where W is the work done ON the system. Q is NOT the same as the term 'thermal energy' is used in this article. AMSask ( talk) 14:06, 20 July 2014 (UTC)
I removed some language from the lede. This whole article is problematic - "thermal energy" is not a standard term in physics, and for good reason (it cannot be defined in general). But to the extent it makes sense, it is certainly not the "average kinetic energy per particle" - one could better define it by subtracting the average velocity first, but for that we need a reliable source, and I doubt there is one (hyperphysics certainly doesn't count as such). Anyway, I tried to make the lede less wrong. Waleswatcher (talk) 17:01, 14 August 2014 (UTC)
Arguably thermal energy is a bulk property, not one of individual particles: but the kinetic energy of each particle contributes to it. This is a true statement, with a reference provided. So there is no reason to delete it. ---- Ehrenkater ( talk) 17:34, 14 August 2014 (UTC)
The reference is not to a reliable source, and "average KE per particle" is manifestly not the correct definition of thermal energy, or thermal anything. There is an extensive discussion of that further up the talk page, where several editors agreed (and the only disagreement was from an editor that I believe has been banned from editing any thermal physics articles). In brief, consider a zero temperature crystal. Now boost to a frame where the crystal is moving with velocity v. The temperature of the crystal is still zero, so by the definition in the first sentence of the lede, the thermal energy is zero. But by the definition of "average KE per particle", the crystal now has an arbitrarily large thermal energy. Waleswatcher (talk) 17:56, 14 August 2014 (UTC)
The problem is that "thermal energy" has no reliable, universally accepted meaning. There is a difference between the Ency. Brit. and Hyperphysics definitions (the latter not including potential energy). Both definitions, however, represent mainstream usage of the term. The objection to "average KE per particle" is addressed by referring to the "average KE per particle as measured in the frame of reference of the center of mass of the system". That is implicit in the Hyperphysics definition. Temperature is always measured in the frame of reference of the center of mass. It is understood that the average KE per particle does not take into account the mechanical kinetic energy of the system as a whole. AMSask ( talk) 18:31, 25 August 2014 (UTC)
But, however it is used, it does refer to energy possessed by the particles in the system by virtue of temperature.
COMMENT: What? I don't know what your sentence means. How can one even TELL what part of the internal energy of a system is "possessed by virtue of temperature"? That sounds like a magic incantation. Do you mean the energy that goes in as heat while you warm the thing up from absolute zero? Like Q = ∫Cv dT from 0 K to whatever temp you have? And that Q is your "thermal energy"?
Well, let's take a real example. I have a gram of vitrified water at absolute zero (or to close to that, that the difference doesn't matter). I prepared it by dropping liquid water mist drops at 0 C (273 K) onto a copper plate cooled with liquid helium, and when the water solidified so quickly that it didn't have time to crystallize, I collected the vitrified powder as solid water "glass" powder, and cooled it some more. Now, I compare this to a gram of pure ice at the same temp, which I prepared by letting it freeze into a perfect crystal of ice at 273 K, then cooling the ice crystal to 0 K.
Now, clearly I removed 79 cal less heat from the glass, since I didn't have to remove the heat of crystallization. But both specimens of 1 gram solid water are now at 0 K. So which one has the more thermal energy? Do they have zero thermal energy?? Are they the same since they are at the same temperature? Or different, because I removed more heat from the crystal than the glass. Clearly the glass has some residual entropy (the crystal has none, by the third law of thermodynamics), but does the glass have more thermal energy along with that entropy? That's a problem.
Now for the fun: I heat up both samples, in a calorimeter until I have a gram of liquid water at 273 K (0 C). This time it takes 79 cal more heat to get the ice crystal to 0 C liquid than it does to get the glass to the same state. But in the end I have two absolutely identical samples of liquid water. Which one holds the more thermal energy? Are they the same (since they are the same substance)? Or do they differ by virtue of their different histories, and I know it, because I added 79 more cal to one of them from absolute zero, and I put a mark on that container, so I know which water sample was the one that had more heat added. Clearly, the heat capacity integral fails here. S B H arris 03:11, 12 September 2014 (UTC)
I disagree with the use of the term to mean internal energy, because there already is a term for internal energy: “internal energy.” I don’t know what a “mean” internal energy could be that internal energy isn’t already. “Mean” suggests you average something out. With internal energy you add microscopic quantities of energy UP.
Calling internal energy “thermal” is wrong, as there are many components of internal energy that are NOT thermal. Every time I do work upon an object (for example) I raise its internal energy, but not thermally. For example, I can bang on a bit of ice with a hammer, or compress it, or whatever, till it partly melts, but I haven’t added any heat. I did work. Nor did its temperature rise. I can also charge an (ideal) battery and raise its internal energy, but that’s not a thermal process either (it is chemical and electric, and the ideal battery doesn’t get any warmer). So deciding to call internal energy “thermal” is a bad idea for lots of processes that do change internal energy.
For similar reasons it’s also a bad idea to decide that some PART of an increase in internal energy is “thermal”, since how do you know what part is “thermal”? There’s no way to decide. Once the ice has melted, you don’t know if it was by heating it or by banging or rubbing it. Or putting it in a dielectric chamber and subjecting it to an alternating E field. The end product is the same, and you’ve already agreed that the history of how it got that way is not only unimportant, but unfair to require. And yet some sites on the web have decided that “thermal energy” is what heat becomes after it’s passed into an object and is no longer heat because it’s not in transit. And as though, when it’s “in” an object, you can still tell it is “thermal” energy and not some other kind.
Other sites declare that heat is “thermal energy” in transit, but only WHILE it is in transit, and thus, only while it is classic heat. That’s actually the only definition that I can agree with and that makes any sense, but it’s a pretty short one (I don’t know if it’s worth more than a paragraph). And also you need to make sure the reader understands that heat and thermal energy in this case BOTH go away once the transfer stops. And after that, they become internal energy, and NOT any longer thermal energy. There is no static thermal energy by any definition that is scientifically useful.
Some definitions of thermal energy decide to add up (integrate) the heat input into an object and continue to call that “thermal energy” even after it has been added, so that (in this definition) an object can contain (supposedly) contain static thermal energy. But it’s not safe to do that in many situations, because (as noted) heat can change into many types of energy after it is added and you can’t tell by temperature or by any other means what part of the internal energy of an object got there by means of heating it. That’s true of heat-absorbing chemical reactions, for example. There are also ways that work can leave a system when heat was put into it, as for example when you heat a gas at constant pressure. That (of course) takes more heat to change the temperature than heating it at constant volume, but only because some heat was transformed into work. In all cases, adding up the thermal energy added, in that case, does NOT give you the internal energy change. That’s how students get into trouble.
In some heat transfer texts, in solid or liquid systems where volume changes and system work inputs and outputs are small enough to neglect, and also chemical energies and phase change (latent) heats are (somehow) accounted for, or don’t exist, you can pretend that all internal energy changes are due to heating, so that heat acts almost like a fluid which is conserved and can be handled as such, even when it stops flowing. In that case, “total history of heat flow” sometimes loosely gets conflated with internal energy (since ∆U = ∆Q when all other energy sources and sinks are zero), but it’s always a bad habit. Energy is always conserved, but heat, in too many cases, is not.
Definitions of thermal energy that rely on “kinetic energy” or “translation kinetic energy” (aren’t they the same thing?) are clearly wrongheaded, as both of these things are directly proportional to temperature, and clearly neither internal energy change nor heating need have anything to do with temperature change, as all the phase changes examples above show. And we talked about how heat capacities can change due to external work or chemical storage. The whole point of potential energy is that it doesn’t change T because it’s potential and NOT kinetic.
A bulk property? I can put heat into an ice cube and melt some of it. The temperature doesn't change and the mean kinetic energy of the particles doesn't change either (since that's what temperature IS). But I have increased its internal energy, have I not? That heat energy went SOMEWHERE, did it not? The internal energy must have increased. So have I increased its "thermal energy"? You see the definitional problem here. You can't connect internal energy directly with either temperature or kinetic energy. Some of internal energy is potential energy. But it gets put in, and taken out, as heat. Is that part "thermal energy" or not? The hyperphysics definition completely finesses that problem by going for a system of free particles. S B H arris 06:11, 5 September 2014 (UTC)
Encylopedia Brittanica is a tertiary source, not a secondary source. It's not a reliable source (by wiki's standards WP:RS) for anything, let alone the main topic of an article. The same goes (even more) for hyperphysics. Are there in fact any reliable (by wiki's standards) sources for "thermal energy"? If not, the article should be deleted. If so, please add them to the lede. If "thermal energy" is really a concept in physics, then it would be at the basis of statistical mechanics and thermodynamics and be discussed in every text on the subject. Waleswatcher (talk) 12:21, 6 September 2014 (UTC)
No reliable sources have been added, presumably because there are none. This article probably should to be deleted entirely, but short of that, I intend to continue to delete the unsourced material. Waleswatcher (talk) 16:21, 1 May 2016 (UTC)
Is our technology capable of determining whether or not thermal dynamic energy is a viable source? Sustainability plus stability are the two factors are far more important. BlueFireSnake ( talk) 20:10, 10 January 2018 (UTC)
I proposed this article for deletion because, as it was written before, it was both wrong and unsourced (and it remained that way for years). As it's written now it's OK in the sense that it is not wrong, but given that its content is that "thermal energy" is used as a loose synonym for some other things (all with their own wiki pages), plus a little bit of physics about the differences between those things, should we just convert it to a DAB page? Waleswatcher (talk) 14:29, 23 April 2018 (UTC)
Here's a sandbox with what I intend to do to this article: /info/en/?search=User:Waleswatcher/sandbox . Comments? Waleswatcher (talk) 13:16, 30 April 2018 (UTC)
This page is so badly written that I am using it as an example for the CRAAP Test for studying sources on the Internet. — Preceding unsigned comment added by 71.30.225.230 ( talk) 00:24, 26 March 2020 (UTC)
I have undone this good faith edit.
Heat transfer does not distinguish kinetic from potential energy. Chjoaygame ( talk) 16:12, 12 January 2021 (UTC)
This https://en.wikipedia.org/?title=Thermal_energy&type=revision&diff=1104461578&oldid=1102799939 edit posts a topic rather different from the main direction of this article. This article is about a technical term that is used loosely in several topics of physics, to refer several different manifestations of energy. These uses of the word 'thermal' are quite abstract and are rather different from its use in the new edit, which is about large scale industry, a far more concrete topic. I suggest that the new edit should be moved to form a stub of a new industry-oriented article. It is evident that the editor who posted the new edit expects that there will be more comparable industrial projects. Chjoaygame ( talk) 07:38, 17 August 2022 (UTC)
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I'm not saying I'm an expert, and I'm not here trying to squash free thought or expression, but my substantial background in thermodynamics provides me some perspective in the supposed field of this article. My perspective is that while I have seen one US High school text present a concept of "thermal energy" when teaching elementary concepts of kinetic theory of ideal gases, and I offer no opinion as to the doubtful pedagogical merits of such use, and I may possibly have used this term inappropriately at a cocktail party once, and if so I'm truly sorry, yet beyond that I am not aware of scientific authority which articulates or advocates the generalizations and definitions offered in this article. Thermodynamics is generally regarded by Physicists and Chemists as falling into the philosophical realm of a "science" which concerns itself with HEAT, with WORK, with TEMPERATURE and ENTROPY, with PRESSURE and VOLUME, it conventionally defines ENTHALPY (H), GIBBS FREE ENERGY (G), HELMHOLTZ ENERGY (F), and INTERNAL ENERGY (E) but nowhere do I find anywhere, including the Britannica article cited, an authoritative exposition or definition of "THERMAL ENERGY". The author may have (incorrectly) confabulated with INTERNAL ENERGY which, for an ideal gas has the properties s/he states, but for no real substance. I am aware of several prior editing wars related to this "thermal energy" concept in other articles, and have seen it persistently inserted into fundamental definitions in the Wikipedia. I've made no modifications here and I'm NOT starting an editing war here, but my technical opinion is this article should provide other authoritative references (which I doubt can be found), or should be greatly revised and reviewed by a technical expert having a PhD in the field or by a PhD teaching upper division thermodynamics in Physics, Chemistry, or Engineering. —Preceding unsigned comment added by 76.191.132.120 ( talk) 00:55, 23 January 2008 (UTC)
So the difference between kinetic energy on a atomic/subatomic/elementary/quantum level and thermal energy is.....?
The Description section is inaccurate in many ways:
It should be rewritten. Warning added to article. -- Tromer 01:27, 16 October 2005 (UTC)
It appears that this is mostly a web page about thermal energy phrased entirely in neologisms, using newly invented English terms instead of the traditional Greek and Latin; indeed there's a change comment on the Thermal energy page saying, "moved Thermal energy to Warmal inwork: English term instaed of Greek", although I can't find earlier versions of the thermal energy page in the history. As such it's amusing to read, and it seems at least mostly correct, but it would probably be more useful if phrased in the traditional words, so that its readers could communicate with people using the traditional terms. Kragen Sitaker 02:08, 22 December 2005 (UTC)
The Description section is not just inaccurate, it is absolutely awful. It should be rewritten completely. Thermal energy is NOT quantified by temperature; "infrared radiation often linked to thermal energy" is a very vague phrase; the discussion of oscillators and their relation to thermal energy is unclear; the second law of thermodynamics is stated in a very curious and not very useful form ("thermal energy is special among the types of energy" is unphysical and vague, and "heat is a form of energy of lower quality" is completely meaningless). In short, this section needs to be completely rewritten, preferably by a physicist. 131.111.8.96 05:13, 3 January 2006 (UTC)
Thermal energy is not heat. It is the energy of the particles in an object. The temperature of an object is just the average amount of energy per particle but thermal energy is the total amount of energy in something.
MYT 03:52, 23 February 2006 (UTC)
I've fixed some of the errors in the article. With part about the laws of thermodynamics, I just cut that out completely and added a link to its main article at the end. They are really not necessary and not that relevant to the subject. I could say that about much of the rest too. Well, the thing's better than before, and that's all that I claim. -- myncknm 05:47, 11 March 2006 (UTC)
Hmm, the page seems to have been blanked and restarted. Good? I think it was. There was a lot of irrelevancy and badness in there before. -- myncknm 01:41, 24 May 2006 (UTC)
I have looked at many topics about thermal energy and have found no definition. It is energy caused by heat —The preceding unsigned comment was added by Axiomwheeler ( talk • contribs) 04:07, 12 February 2007 (UTC).
I completely rewrote and condensed this (also removed the picture that had little to do with 'thermal energy'); the old version was poorly written and quite redundant. If anyone wants to expand it, they should start from my text. The way, the truth, and the light 07:50, 6 June 2007 (UTC)
The first line of this page begins, 'Thermal energy or thermodynamic energy, often called heat...'. Shouldn't 'thermal energy' and 'heat' have the same page, then? I am not a physicist, but based on my understanding I don't see the need for separate articles on these subjects. Since heat is a far higher quality article than this one, I suggest merging 'thermal energy' into that page. Terraxos 05:51, 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 20:42, 18 June 2007 (UTC)
This page should be deleted rather than merged- I can't see any new material here. Thermal energy has a meaning but not one that is different from internal energy (I don't know what whoever wrote this thinks is the internal energy of an object at absolute zero). Heat transfer is the mechanism of energy transfer between objects of different temperatures. Most of this article is about heat transfer, not thermal energy. MAG1 22:34, 18 June 2007 (UTC)
I think we should keep these pages separate. I'll try to elucidate the differences when I have a chance in a couple weeks. In the meantime I think there should be no deletions or mergers. Scott.medling 22:49, 24 June 2007 (UTC)
I think the three should be merged, as the differences are subtle enough to explain all in the same place. This is the way they are introduced in textbooks, too. See Talk:Heat#Merger_with_Thermal_energy. — Omegatron 23:44, 24 June 2007 (UTC)
I realize this is an oudated discussion, but I need to point out something for the benefit of anyone reviewing it. Thermal energy and internal energy are not the same thing. Thermal energy is defined as energy from molecular motion, whereas internal energy is all the energy inside a system and thus also includes chemical bond energy and so on (ie ). Having said that, here's where the confusion arises. Some disciplines might omit from their definitions those components of internal energy which are not relevant to them. This is because when we work with internal energy, we're only interested in how it changed (or could change). Any component which does not change will not affect our calculations and can essentially be ignored. For example, mechanical engineers and non-nuclear physicists can totally ignore the chemcial and nuclear energy in their systems. This energy will never be accessible to them so it is as if it is not even there. (This may be why some in this discussion have argued that ; if their only training is in mechanics, then they may not have seen it defined any other way!) But a chemist knows there's also chemical energy inside a system. And a nuclear physicist knows that there's nuclear energy in it. Since Wikipedia is for all disciplines, we need to keep in mind that internal energy actually includes much more than just thermal energy. Riick ( talk) 16:28, 23 August 2010 (UTC)
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) people if you don't know what thermal energy is don't ask me —Preceding unsigned comment added by 204.2.37.50 ( talk) 21:08, 30 January 2008 (UTC)
why they call thermal energy for energy of heat an —Preceding unsigned comment added by 76.30.143.169 ( talk) 14:42, 25 October 2008 (UTC)
Thermal Energy:1 bottle Litter,a large ballon,a bowl of hot water[not boling],a bowl of ice cold water,and a small rock.p.s this is materials that you need for a science project!
Bold textTHE BEST!!!!!!!!! —Preceding unsigned comment added by 76.108.50.244 ( talk) 01:43, 20 March 2009 (UTC)
This is a crapppppppppy web come onnnn wat info u give???????? NOTHING NOTHING and more NOTHING U cant even tell me wat heat energy is!!!!!!!!!! —Preceding unsigned comment added by 41.242.191.163 ( talk) 19:42, 21 July 2009 (UTC)
Although this has been discussed before without coming to a clear conclusion, I propose merging this page with Internal energy. Specifically, all that needs to be said about this topic is already said in Internal energy#Composition, where, compared to this article, it's said much more clearly and without the added nonsense. Djr32 ( talk) 19:40, 5 October 2009 (UTC)
The article was rewritten and reinstituted on 2010-11-03T23:06:30 by User:Kbrose.
I'm a Physics teacher and I'd like to share my opinion on the definition of thermal energy. First of all, thermal energy and heat are not the same. And I'm glad this article shows this difference perfectly. Thermal energy is a component of internal energy whereas heat is a form of energy transfer (the other forms are work and mass transfer). Now, some people consider thermal energy only to be the quantity of kinetic energy of all the molecules, atoms, electrons, etc. of a system. I do not like this definition because it does no consider what happens when a system absorbs or release (internal) energy while changing from a state to another. For example, consider what happens when a piece of ice starts abosorbing energy, initially its tempeature increases and, therefore, it means that its internal energy has increased, specifically its thermal energy (becauses its internal kinetic energy increased). If the piece of ice keeps absorbing energy, eventually it will not increase its temperature for a while but will change its state from solid to liguid. The question is: WHAT COMPONENT OF THE INTERNAL ENERGY INCREASED DURING THIS STATE CHANGE? The nuclear energy? Nop! Because nothing happened at the nuclear level. The chemical energy? Nop! Because no chemical bonds have been created or destroyed. When the state changes, it means that the spatial arrangement of the molecules of the system changed. So, what component of the internal energy accounts for this? I say, necessarily, the thermal energy but if it is defined to consider ONLY the internal kinetic energy it WILL NOT BE USEFUL to answer this key question, but, if it is defined to consider ALSO the state of the system, then, that energy absorbed by the piece of ice to change its state will represent an increment in the thermal energy. When I teach my classes I teach that thermal energy has two components:
Sensible energy: The internal kinetic energy of the system and,
Latent energy: The potential energy associated to the state (solid, liquid, gas, plasma, etc.) of the system.
In my classes, sensible energy and sensible heat are not the same. Sensible heat is defined as the amount of heat (the quatity of energy that must be absorbed or released) necessary to produce a change in temperature. Besides, latent energy and latent heat are not the same either. Latent heat is the amount of heat (the quatity of energy that must be absorbed or released) necessary to produece a change of state.
So, by using "my" definition, the problem is solved. Pitifully, this definition is not widely used. An example of this case is this article. Here, thermal energy only considers the internal kinetic energy but not the potential energy relative to the state of the system. There's a couple of websites that share my point of view:
http://www.ifpaenergyconference.com/Thermal-Energy.html http://wiki.answers.com/Q/Does_thermal_energy_increase_during_a_phase_change
George Rodney Maruri Game ( talk) 03:03, 19 November 2010 (UTC)
Oh, I'm so glad for your words. You have said many things which are completely true. First of all the sources are not "that" reliable. I understand that and besides the first constradicts itself. Obviously for me it's been really hard to find good sources. Thanks for answering "my question" (potential energy) in fact, it's all about terms. Potential energy is the energy associated to the spatial arrangement or configuration of the components and, as you might have noticed, I define latent energy as "the potential energy associated to the state (solid, liquid, gas, plasma, etc.) of the system." It means we share our point of view only with different terms. In short, LATENT ENERGY IS POTENTIAL ENERGY. The other question is "Should we consider latent energy (potential energy) as a part of thermal energy?". If we say "yes"... let's see... if temperature only has to do the average "kinetic component", it is, the sensible energy (not heat, remember "my" definition?, he, he), it means that temperature wouldn't be related to the average of the total thermal energy but only to one component. But if the answer is "no", temperature would give a reading of the average of all the "thermal energy". Thank you for answering. I hope some day all this matter finally ends up with a world-wide agreement regardless of the terms but with the same "idea". George Rodney Maruri Game ( talk) 16:41, 30 November 2010 (UTC)
Again, thanks for your comments. To be honest, reading your words enhance my own learning about this topic. I agree with you practically in everything. But I have this "maniatic" custom of "labeling" every little thing. So, what do you think of these (obviusly as you have stated some of my ideas are unsupported but I want to know your opinion):
Chemical (potential) energy: The potential energy associated to the intra-molecular (inter-atomic) configuration of a substance.
???? (potential) energy: The potential energy associated to the inter-molecular configuration (lattice). May I suggest ???? = "latent" (I know there are no supportive sources, but just tell me your opinion about the idea, I´ve come to acknowledge your great insight about all this)
Thermal energy: Total kinetic energy at both inter-molecular and inter-atomic levels of a sample of substance.
Sensible energy: Average kinetic energy at both inter-molecular and inter-atomic levels.
Temperature: A "measure" of the average kinetic energy (sensible energy) at both inter and inter-atomic levels.
Latent heat: Energy necessary to produce a state change.
Sensible heat: Energy necessary to produce a temperature change.
I appreciate so much to have the opportunity to share my ideas with someone who, in my opinion, has unselfishly brought a great level of comprehension relative to this topic (at least for me because I´m still learning, too young to look like a Physics teacher, he, he, he). I understand that even if you agree on my "ideas" they won´t make it into the article due to lack of reliable, published and widely accepted sources.
George Rodney Maruri Game (
talk)
18:49, 3 December 2010 (UTC)
Simply wonderful and precise! Finally I think I've come to understand all this "almost perfectly", because I still have a couple of questions, though. Thank you so much for your patience. One question is: Is temperature an exact reading of the average kinetic energy of a sample or just a "measure"? That way there wouldn't be no need for two terms (what I proposed as sensible energy would be the same as temperature: The average kinetic energy at the inter-molecualar and inter-atomic levels). The other questions is (or rather request): Would it be possible that this explanation you have given (and further ones you might give in the future) to me can make it into this article, please? I mean if it has been so valuable to me, maybe others can get some benefit also. You know, it is true that I teach Physics but just at the high school level and I bet you have studied a lot more than me, probably you teach at a college or university or your work requires you to understand all this very well. Nevertheless, I think that all this confusion remains because all this thing is not taught earlier and correctly (at high school!). That way colleges or universities teachers wouldn't have to "destroy" so many myths (fix misconceptions) about internal energy, thermal energy, heat and temperature. Thank you again. I hope I'm not taking so much of your time. George Rodney Maruri Game ( talk) 16:43, 5 December 2010 (UTC)
What can I say but thank you. Now, doubts are just memories! I think I will come here to the talk page every time I need to look for information on this topic, he, he. See you around... George Rodney Maruri Game ( talk) 02:36, 7 December 2010 (UTC)
The article says: In the microscopical description of statistical physics, the thermal energy is identified with the mechanical kinetic energy of the constituent particles or other forms of kinetic energy associated with quantum-mechanical microstates.
The distinguishing difference between the terms kinetic energy and thermal energy is that thermal energy is the mean energy of disordered, i.e. random, motion of the particles or the oscillations in the system. The conversion of energy of ordered motion to thermal energy results from collisions.[5]
The reference is not online, but if it actually says this, it is wrong. The thermal energy in an ideal gas is all kinetic energy, but the thermal energy of solids is (on average) twice as much as for gases at the same temperature. This is a simple demonstration that since twice the heat is stored at the same temp in a solid as in a monatomic gas, and since temperature is connnected to mean kinetic energy of atoms, that therefore the extra 100% of energy-content (thermal energy) stored in solids as you raise their temperature, is not kinetic energy, but some other sort of energy (in fact, it is the potential energy component of vibration). So all this is wrong.
Incidentally, some texts (not all) go even further to define "latent heat content" as part of the thermal energy. This makes perfect sense, as latent energy contributes to energy that is absorbed and extracted from systems during heat transfer and stored in the system in the meantime as a thermally accessable reservoir of energy (like any degree of freedom). What else would you call latent heat content, if it participates fully in heat storage, except system thermal energy?
Of course, this makes hash of the "contributes to temperature" definition of thermal energy (unless qualified as being in a single phase), but that definition is not written in stone. A better one is that thermal energy (what used to be called heat content) is that part of internal energy which changes when you add or subtract heat, using a temperature gradient. Very simple. It isn't exactly classical heat capacity times temperature, unless you add a term covering heat absorption due to phase change (where heat capacity is infinite). But phase changes add to the thermal energy ("heat content" in the old terminology) of systems, as anybody using steam condensation to extract heat can tell you. Steam has a thermal energy that the equivalent amount of water at the same temperature, does not. Any engineer would regard it that way. S B H arris 19:47, 6 April 2012 (UTC)
I must fix the thermal energy article, which states that thermal energy is a state function. Nonsense! Except in the limit that no chemical or PV work is done, so that a change in thermal energy becomes a change in internal energy, which is a state function. Otherwise the difference between constant pressure and constant volume heat capacities (which are different for every substance, even if good approximations) show clearly that temperature is path-dependent, and thus so is thermal energy or "heat content." You can get an object to the same temperature in two ways (for example), using two different total amounts of heat dumped into it, if you let it do PV work to get to the state in one case, but not in the other. So δW = 0 and no change in chemical potential and so on, must be specified before we talk of thermal energy in any such fashion. And then indeed, "thermal energy" (an idealized quantity in the limit of no other energies that are reversibly turned into heat at the same time) is that component of internal energy that can be extracted by a temperature gradient. But if you don't make δW = 0, you can, by fiddling with work or other internal heat/chemical potential sources, extract any number of differert amounts of thermal energies from the same object, in passing to a given lower temperature (or to absolute zero, for that matter). If you do so, that makes thermal energy content inherrently ridiculous. S B H arris 01:47, 2 June 2012 (UTC)
The article opens with:
Thermal energy is the part of the total internal energy of a thermodynamic system or sample of matter that results in the system temperature.[1] This quantity may be difficult to determine or even meaningless unless the system has attained its temperature only through heating, and not been subjected to work input or output, or any other energy-changing processes.
Which is not correct.
Thermal energy is that energy in a system due to the (total) kinetic, i.e. including rotational energy, of the particles of the system.
Since there is no requirement for the system to be in equilibrium to 'have thermal energy' then no 'system' temperature can (or needs to) be identified, the thermal energy in a system is merely the sum of the kinetc energy of the particles in the system.
P.S. I notice that the 1st ref. in the article is to an article in Encyclopedia Britannica which of course derives some of its material from Wikipedia. Wikipedia is, of course, not a reliable source. -- Damorbel ( talk) 08:14, 5 November 2012 (UTC)
"For the tenth time half of thermal.... What is your point? In solids the thermal energy is stored in the vibrations of the various bonds making the system a solid. Since these are vibrations the energy is, according to the period of the vibrations, regularly exchanged between kinetic and potential energy and, omitting the tranfer that takes place in non-equlibrium conditions, all the potential energy is changed into kinetic energy, thus they are equal. So the total energy is equal to the maximum potential energy or the maximum kinetic energy or half the potential energy plus half the kinetic energy. If you wish to go further in this matter you may wish to study phonon interactions wherby the nature these vibrational energy processes are given a sound theoretical basis, including thermal conduction. -- Damorbel ( talk) 10:05, 5 November 2012 (UTC)
I have removed the text :-
In engineering and technology, and particularly in fields that deal with civil energy use and conservation in building construction, heating systems, and power generation, heat and thermal energy are often indiscriminately used interchangeably.
from the section: http://en.wikipedia.org/?title=Thermal_energy&oldid=523879256#Distinction_of_thermal_energy_and_heat
Which is preposterous twaddle. I am sure there is no reliable source for this assertion. -- Damorbel ( talk) 13:42, 21 November 2012 (UTC)
Where does this come from? :-
According to the zeroth law of thermodynamics, heat is exchanged between thermodynamic systems in thermal contact only if their temperatures are different,
Surely the second law! (And it should be energy that is exchanged.) -- Damorbel ( talk) 14:07, 21 November 2012 (UTC)
The article has the following in the intoduction:-
Thermal energy is the part of the total internal energy of a thermodynamic system or sample of matter that results in the system temperature.[1]
Which is not at all true. Thermal energy is the energy of particles in motion, it can be linear motion, rotary motion or vibratory motion. The particles do not need to be part of a defined system, not even excepted by the needs of an inertial system.
Worse still there is no direct connection between system temperature and thermal energy. This latter has a refernce to the Encyclopedia Britannica which often uses Wikipedia as a source, what a joke! BTW, anybody know what System temperature is supposed to mean? -- Damorbel ( talk) 15:50, 21 November 2012 (UTC)
I have revised the opening statement according to the above discussion. Of particlar importance is the removal of the link to the Encyclopedia Britannica which appears to have copied its content from a previous version of Wikipedia! -- Damorbel ( talk) 06:35, 21 February 2013 (UTC)
It is obvious nonsense to suggest that putting an object in uniform translatory motion affects its "thermal energy", which is what the last version of the article implied. Thermal energy cannot simply be the average kinetic energy of particles, because "thermal" implies a thermal distribution, and (for example) uniform motion gives every particle the same kinetic energy - which has nothing to do with thermal anything. The real problem is that "thermal energy" doesn't make much sense, and this article should be entirely re-written to reflect that. Waleswatcher (talk) 22:14, 24 February 2013 (UTC)
Bulk particle motion in one direction is not thermal energy. A perfect crystal at 0 K moving half the speed of light, has a hell of a lot of kinetic energy. But it still has no thermal energy, and it still has a temperature of zero. It has the same temperature in all frames, in fact, which is zero. S B H arris 22:36, 25 February 2013 (UTC)
You don't HAVE an argument. It doesn't matter if a meteoroid produces a great deal of heat when it strikes the atmosphere or the earth (or whichever). The point is that its kinetic energy of motion does not make it hot BEFORE it strikes and produces friction. It can (and usually is) moving very fast but is still very cold. This high kinetic energy is not "temperature" or "thermal energy" in space. It is only converted to thermal energy and heat that raises temperature, after it hits. S B H arris 23:23, 27 February 2013 (UTC)
It doesn't apply to temperatures when they are zero, since zero multiplied by any number is zero. An object with a temp of zero in any frame , will have a temp of zero in ALL frames. Of course, that's not true of kinetic energy. Which is why this type of frame- dependent KE doesn't add to temperature.
If you think you can give an object at rest at 0 K a temperature by moving it (or yourself), do you think it will then start to give off thermal IR radiation? Do you think it radiates energy away like this in some frames but not at all in its rest frame? Very funny. S B H arris 18:25, 5 March 2013 (UTC)
Indeed. You have just made a good argument for why the idea of the temperature of a single particle is meaningless. S B H arris 20:25, 6 March 2013 (UTC)
You are the person who asserted that one particle could be said to have a temperature, were you not? Well, it can't. S B H arris 21:55, 6 March 2013 (UTC)
Currently the opening section of this article has:-
In what sense is "potential energy" thermal, i.e. a function of temperature? For example, how can gravitational potential energy be thermal and how can chemical potential energy be thermal.
These are serious inaccuracies not appropriate to Wikipedia. -- Damorbel ( talk) 06:30, 24 May 2013 (UTC)
Further. The following text also appears :-
Thermal energy does not need to be conserved or even strictly upheld to be an important property. Exactly the same can be said for chemical and other forms of potential energy. These are all part of physics, the explanation of observational science. The fact that some quantities are conserved and others not are laws that provide understanding of how physical processes operate in a logical way.
This whole section needs revising to remove the confusion between kinetic and potential energy. -- Damorbel ( talk) 07:21, 24 May 2013 (UTC)
Here is one particular thermal system that has no potential energy. Therefore potential energy can never be thermalised
Um, no, Jheald; I did not say anything like:-
To expand what I said just a little, "gas molecules under pressure in a container do not have potential energy due to intermolecular forces as do the molecules in liquids and solids." To be more explicit the presence (or absence!) of potential energy (in any form) has no influence on temperature , that is why water boils at a constant temperature, freezes at a constant temperature etc., etc. -- Damorbel ( talk) 06:52, 29 May 2013 (UTC)
Can't the thermal energy of a system be defined as as state function something like the following?
Of course, by "in principle", I mean I'm allowing for the hypothetical process mentioned in the definition to take place (arbitrarily close to) remaining at equilibrium and to take the temperature of the system (arbitrarily close) to absolute zero, where the thermal energy becomes zero. Doesn't this definition constitute a state function, i.e. its value doeesn't depend on how the system got into that state, correct? It is an operational definition in that you can measure this quantity of energy to some precision by cooling the system in a certain way. If this definition isn't consistent with the concept of thermal energy, when and why do they differ?
DavRosen ( talk) 05:54, 21 July 2013 (UTC)
It might be helpful to recognize that there are of course numerous interconversions between forms of energy and that only TOTAL energy of the UNIVERSE is conserved. An "isolated" system is a reasonable facsimile. Given this it might be worth questioning the tendency to single out thermal energy as particularly ill-defined because of the fact of energy interconversion. The same can be said of all forms of energy except for total energy of the universe or isolated system. Thermal energy is simply an especially good example of a form of energy with many interconversions both input and output. Davidr222 ( talk) 16:15, 12 June 2014 (UTC)
The term 'Thermal energy' is a not used in thermodynamics. It has no precise definition so it can mean different things in different contexts. This means that it should not have its own Wikipedia page. In my view an article on 'Thermal Energy' should redirect to Internal energy and Heat.
The article incorrectly states:
1. "Thermal energy is the part of the total potential energy and kinetic energy of an object or sample of matter that results in the system temperature." Potential energies and non-translational kinetic energies of molecules do not contribute to the temperature of a substance.
2. "It is represented by the variable Q, and can be measured in joules." Q is a defined term in thermodynamics. In a thermodynamic process, Q represents heat flow, which is essentially energy transferred to or from a system by means other than mechanical work ie.: The First Law of Thermodynamics: Q + W = ΔU where W is the work done ON the system. Q is NOT the same as the term 'thermal energy' is used in this article. AMSask ( talk) 14:06, 20 July 2014 (UTC)
I removed some language from the lede. This whole article is problematic - "thermal energy" is not a standard term in physics, and for good reason (it cannot be defined in general). But to the extent it makes sense, it is certainly not the "average kinetic energy per particle" - one could better define it by subtracting the average velocity first, but for that we need a reliable source, and I doubt there is one (hyperphysics certainly doesn't count as such). Anyway, I tried to make the lede less wrong. Waleswatcher (talk) 17:01, 14 August 2014 (UTC)
Arguably thermal energy is a bulk property, not one of individual particles: but the kinetic energy of each particle contributes to it. This is a true statement, with a reference provided. So there is no reason to delete it. ---- Ehrenkater ( talk) 17:34, 14 August 2014 (UTC)
The reference is not to a reliable source, and "average KE per particle" is manifestly not the correct definition of thermal energy, or thermal anything. There is an extensive discussion of that further up the talk page, where several editors agreed (and the only disagreement was from an editor that I believe has been banned from editing any thermal physics articles). In brief, consider a zero temperature crystal. Now boost to a frame where the crystal is moving with velocity v. The temperature of the crystal is still zero, so by the definition in the first sentence of the lede, the thermal energy is zero. But by the definition of "average KE per particle", the crystal now has an arbitrarily large thermal energy. Waleswatcher (talk) 17:56, 14 August 2014 (UTC)
The problem is that "thermal energy" has no reliable, universally accepted meaning. There is a difference between the Ency. Brit. and Hyperphysics definitions (the latter not including potential energy). Both definitions, however, represent mainstream usage of the term. The objection to "average KE per particle" is addressed by referring to the "average KE per particle as measured in the frame of reference of the center of mass of the system". That is implicit in the Hyperphysics definition. Temperature is always measured in the frame of reference of the center of mass. It is understood that the average KE per particle does not take into account the mechanical kinetic energy of the system as a whole. AMSask ( talk) 18:31, 25 August 2014 (UTC)
But, however it is used, it does refer to energy possessed by the particles in the system by virtue of temperature.
COMMENT: What? I don't know what your sentence means. How can one even TELL what part of the internal energy of a system is "possessed by virtue of temperature"? That sounds like a magic incantation. Do you mean the energy that goes in as heat while you warm the thing up from absolute zero? Like Q = ∫Cv dT from 0 K to whatever temp you have? And that Q is your "thermal energy"?
Well, let's take a real example. I have a gram of vitrified water at absolute zero (or to close to that, that the difference doesn't matter). I prepared it by dropping liquid water mist drops at 0 C (273 K) onto a copper plate cooled with liquid helium, and when the water solidified so quickly that it didn't have time to crystallize, I collected the vitrified powder as solid water "glass" powder, and cooled it some more. Now, I compare this to a gram of pure ice at the same temp, which I prepared by letting it freeze into a perfect crystal of ice at 273 K, then cooling the ice crystal to 0 K.
Now, clearly I removed 79 cal less heat from the glass, since I didn't have to remove the heat of crystallization. But both specimens of 1 gram solid water are now at 0 K. So which one has the more thermal energy? Do they have zero thermal energy?? Are they the same since they are at the same temperature? Or different, because I removed more heat from the crystal than the glass. Clearly the glass has some residual entropy (the crystal has none, by the third law of thermodynamics), but does the glass have more thermal energy along with that entropy? That's a problem.
Now for the fun: I heat up both samples, in a calorimeter until I have a gram of liquid water at 273 K (0 C). This time it takes 79 cal more heat to get the ice crystal to 0 C liquid than it does to get the glass to the same state. But in the end I have two absolutely identical samples of liquid water. Which one holds the more thermal energy? Are they the same (since they are the same substance)? Or do they differ by virtue of their different histories, and I know it, because I added 79 more cal to one of them from absolute zero, and I put a mark on that container, so I know which water sample was the one that had more heat added. Clearly, the heat capacity integral fails here. S B H arris 03:11, 12 September 2014 (UTC)
I disagree with the use of the term to mean internal energy, because there already is a term for internal energy: “internal energy.” I don’t know what a “mean” internal energy could be that internal energy isn’t already. “Mean” suggests you average something out. With internal energy you add microscopic quantities of energy UP.
Calling internal energy “thermal” is wrong, as there are many components of internal energy that are NOT thermal. Every time I do work upon an object (for example) I raise its internal energy, but not thermally. For example, I can bang on a bit of ice with a hammer, or compress it, or whatever, till it partly melts, but I haven’t added any heat. I did work. Nor did its temperature rise. I can also charge an (ideal) battery and raise its internal energy, but that’s not a thermal process either (it is chemical and electric, and the ideal battery doesn’t get any warmer). So deciding to call internal energy “thermal” is a bad idea for lots of processes that do change internal energy.
For similar reasons it’s also a bad idea to decide that some PART of an increase in internal energy is “thermal”, since how do you know what part is “thermal”? There’s no way to decide. Once the ice has melted, you don’t know if it was by heating it or by banging or rubbing it. Or putting it in a dielectric chamber and subjecting it to an alternating E field. The end product is the same, and you’ve already agreed that the history of how it got that way is not only unimportant, but unfair to require. And yet some sites on the web have decided that “thermal energy” is what heat becomes after it’s passed into an object and is no longer heat because it’s not in transit. And as though, when it’s “in” an object, you can still tell it is “thermal” energy and not some other kind.
Other sites declare that heat is “thermal energy” in transit, but only WHILE it is in transit, and thus, only while it is classic heat. That’s actually the only definition that I can agree with and that makes any sense, but it’s a pretty short one (I don’t know if it’s worth more than a paragraph). And also you need to make sure the reader understands that heat and thermal energy in this case BOTH go away once the transfer stops. And after that, they become internal energy, and NOT any longer thermal energy. There is no static thermal energy by any definition that is scientifically useful.
Some definitions of thermal energy decide to add up (integrate) the heat input into an object and continue to call that “thermal energy” even after it has been added, so that (in this definition) an object can contain (supposedly) contain static thermal energy. But it’s not safe to do that in many situations, because (as noted) heat can change into many types of energy after it is added and you can’t tell by temperature or by any other means what part of the internal energy of an object got there by means of heating it. That’s true of heat-absorbing chemical reactions, for example. There are also ways that work can leave a system when heat was put into it, as for example when you heat a gas at constant pressure. That (of course) takes more heat to change the temperature than heating it at constant volume, but only because some heat was transformed into work. In all cases, adding up the thermal energy added, in that case, does NOT give you the internal energy change. That’s how students get into trouble.
In some heat transfer texts, in solid or liquid systems where volume changes and system work inputs and outputs are small enough to neglect, and also chemical energies and phase change (latent) heats are (somehow) accounted for, or don’t exist, you can pretend that all internal energy changes are due to heating, so that heat acts almost like a fluid which is conserved and can be handled as such, even when it stops flowing. In that case, “total history of heat flow” sometimes loosely gets conflated with internal energy (since ∆U = ∆Q when all other energy sources and sinks are zero), but it’s always a bad habit. Energy is always conserved, but heat, in too many cases, is not.
Definitions of thermal energy that rely on “kinetic energy” or “translation kinetic energy” (aren’t they the same thing?) are clearly wrongheaded, as both of these things are directly proportional to temperature, and clearly neither internal energy change nor heating need have anything to do with temperature change, as all the phase changes examples above show. And we talked about how heat capacities can change due to external work or chemical storage. The whole point of potential energy is that it doesn’t change T because it’s potential and NOT kinetic.
A bulk property? I can put heat into an ice cube and melt some of it. The temperature doesn't change and the mean kinetic energy of the particles doesn't change either (since that's what temperature IS). But I have increased its internal energy, have I not? That heat energy went SOMEWHERE, did it not? The internal energy must have increased. So have I increased its "thermal energy"? You see the definitional problem here. You can't connect internal energy directly with either temperature or kinetic energy. Some of internal energy is potential energy. But it gets put in, and taken out, as heat. Is that part "thermal energy" or not? The hyperphysics definition completely finesses that problem by going for a system of free particles. S B H arris 06:11, 5 September 2014 (UTC)
Encylopedia Brittanica is a tertiary source, not a secondary source. It's not a reliable source (by wiki's standards WP:RS) for anything, let alone the main topic of an article. The same goes (even more) for hyperphysics. Are there in fact any reliable (by wiki's standards) sources for "thermal energy"? If not, the article should be deleted. If so, please add them to the lede. If "thermal energy" is really a concept in physics, then it would be at the basis of statistical mechanics and thermodynamics and be discussed in every text on the subject. Waleswatcher (talk) 12:21, 6 September 2014 (UTC)
No reliable sources have been added, presumably because there are none. This article probably should to be deleted entirely, but short of that, I intend to continue to delete the unsourced material. Waleswatcher (talk) 16:21, 1 May 2016 (UTC)
Is our technology capable of determining whether or not thermal dynamic energy is a viable source? Sustainability plus stability are the two factors are far more important. BlueFireSnake ( talk) 20:10, 10 January 2018 (UTC)
I proposed this article for deletion because, as it was written before, it was both wrong and unsourced (and it remained that way for years). As it's written now it's OK in the sense that it is not wrong, but given that its content is that "thermal energy" is used as a loose synonym for some other things (all with their own wiki pages), plus a little bit of physics about the differences between those things, should we just convert it to a DAB page? Waleswatcher (talk) 14:29, 23 April 2018 (UTC)
Here's a sandbox with what I intend to do to this article: /info/en/?search=User:Waleswatcher/sandbox . Comments? Waleswatcher (talk) 13:16, 30 April 2018 (UTC)
This page is so badly written that I am using it as an example for the CRAAP Test for studying sources on the Internet. — Preceding unsigned comment added by 71.30.225.230 ( talk) 00:24, 26 March 2020 (UTC)
I have undone this good faith edit.
Heat transfer does not distinguish kinetic from potential energy. Chjoaygame ( talk) 16:12, 12 January 2021 (UTC)
This https://en.wikipedia.org/?title=Thermal_energy&type=revision&diff=1104461578&oldid=1102799939 edit posts a topic rather different from the main direction of this article. This article is about a technical term that is used loosely in several topics of physics, to refer several different manifestations of energy. These uses of the word 'thermal' are quite abstract and are rather different from its use in the new edit, which is about large scale industry, a far more concrete topic. I suggest that the new edit should be moved to form a stub of a new industry-oriented article. It is evident that the editor who posted the new edit expects that there will be more comparable industrial projects. Chjoaygame ( talk) 07:38, 17 August 2022 (UTC)