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I have 'undone' here [1]
It is a fact that the internal energy of an isolated system is conserved, that is why it is called isolated.
Whatever the 'law' says or requires or even demands, it does not govern the facts. -- Damorbel ( talk) 17:50, 6 February 2013 (UTC)
Suppose an isolated system was in a state of absolute motion. How would it know its (heat) condition of kinetic energy of motion? WFPM ( talk) 00:16, 6 March 2013 (UTC)
Since the common concept of heat is its association with 'hotness' or 'coldness' i.e. temperature, surely this should be explained in the opening section as well as the role of temperature difference? -- Damorbel ( talk) 16:45, 8 March 2013 (UTC)
Currently the article says:-
which makes heat independent of temperature, it would also make heat a conserved quantity. Would you care to confirm that this is what you mean? -- Damorbel ( talk) 21:27, 10 March 2013 (UTC)
If heat is not independent of temperature, why does the article, in the opening statement, say " Heat flow from hotter to colder systems occurs spontaneously, "? This statement makes the position (of the article) very clear, that heat is proportional to the difference in temperature, i.e. very clearly not a function of temperature. Is this correct? -- Damorbel ( talk) 06:48, 11 March 2013 (UTC)
There have been countless electrons spilt here on the definition of quantity of energy transferred as heat for this article. I hope I may be forgiven for saying some more about it. I have to say that I think my understanding has improved over the years. In particular I have to say I was partly mistaken in my strictures upon Count Iblis, and I would like to say I am sorry for the times when I went over the top. The matter is not one-sided. I made much of the idea that temperature has to be definable for heat to make sense. I would now speak more carefully. Count Iblis wrote: "Work doesn't have to be mechanical work. The work done by a system is defined as the decrease in the internal energy of a system due to the change of its external parameters." This is one way of seeing things. I would say that in the Carathéodory story, the decrease of internal energy of the system is defined as derived from the measured adiabatic work needed for the change of state. In the Gibbs story, one postulates directly the existence of the internal energy and doesn't derive it from work; of course still one can specialize to a closed system and then derive the work from the postulated internal energy.
I will now try here to say how I think quantity of energy transferred as heat should be defined here.
Quantity of energy transferred as heat is a term of thermodynamics that refers to a specified change of state of a closed system. The initial and final states of the system have defined temperatures and pressures. The quantity of energy transferred as heat is defined as a difference between two quantities of energy transferred as work. One of those quantities is the amount of adiabatic work needed to go between the initial and final state of the change; it refers to the specified change of state only through its initial and final states. The other is the amount of work done by the system on its surroundings during the specified change. This work is in general not adiabatic, and in general includes pressure-volume work and isochoric work. It depends only on the time course of the values of the external variables, including those such as the forces exerted by the surroundings on the walls of the system. How those forces are specified is important. If the work is mediated by a piston, then the external forces that determine the motion of the piston need to be defined. The piston may be driven by a rod. Then the force exerted by the rod on the piston must be specified. The external pressure on the external surface of the piston must also be specified throughout the course of the process, though it might be neglibly small. (I formerly insisted that if that pressure could not be defined during the course of the specified process, then the work could not be defined; that is true. Moreover I insisted that when that pressure was not defined, the external temperature was most likely also not defined. Therefore, I argued, when the external temperature was not defined, the work was not defined. I went too far there. It might sometimes be that the external pressure is defined while external temperature is not; still the work would be defined, as Count Iblis pointed out.) There is no requirement by definition that the external and internal temperatures and piston pressures be equal during the course of the process, but respectively they must be equal in the initial state and in the final state, which are respectively required by classical thermodynamics to be in thermal and mechanical equilibrium with the surroundings. Chjoaygame ( talk) 10:44, 12 March 2013 (UTC)
This edit proposes that a sentence about conduction, cited in the article, appears on page 1 of Partington 1949. In the copy I have here it appears on page 118, and not on page 1. Perhaps the creator of the edit would very kindly tell how he is accessing the source? Chjoaygame ( talk) 08:25, 13 March 2013 (UTC)
From the beginning paragraph "heat is energy transferred from one body to another by thermal interactions." Convection therefore is not a method of heat transfer as the heat is retained by the body and the body itself moved. Strictly speaking convection is a special form of conduction - conduction in a fluid. FlipC ( talk) 10:53, 14 March 2013 (UTC)
The Reif reference is to a textbook, so may well be unreliable. It's definition of heat is inconsistent in that it confuses heat and heat transfer. This is self contradictory, so not even wrong! -- Damorbel ( talk) 15:38, 23 March 2013 (UTC)
You write:-
One of the features that distinguishes heat from energy is that energy is a conserved quantity, whereas it is a fundamental aspect of modern physics is that heat is not a conserved quantity. Is this included in your questions " about the theory of heat "? -- Damorbel ( talk) 06:32, 27 March 2013 (UTC)
The temperature of a solid rises when energy is added, the rising temperature means that the atoms (or molecules) of the solid vibrate with increasing amplitude until, at a particular temperature, the (crystaline?) bonds holding it in solid form, begin to break, it is melting.
Continuing to add energy breaks more bonds without increasing the temperature as more of the solid melts. Finally the solid is completely melted and the temperature starts rising again, with the molecular motion of the liquid increasing further. The amount of energy needed to melt (fuse) a solid is properly called the enthalpy of fusion but is popularly (and mistakenly) called the latent heat of fusion.
From this you can see adding energy can either raise the temperature i.e. increase the heat, or melt the solid when its temperature does not rise. This is similar to boiling - energy is added to a boiling liquid without raising it's temperature; this energy is called the enthalpy of vaporization, often (improperly) called latent heat of vaporization.
Enthalpy is a more accurate term than latent heat because it represents potential energy, the energy of the bonds holding atoms or molecules together in a solid, whereas heat is, as you noted, the kinetic energy of atoms and molecules. -- Damorbel ( talk) 21:30, 27 March 2013 (UTC)
You write:-
Are you saying that this influences the relation of particle energy and temperature? If this was so there would be different Boltzmann constants for solids and liquids.
The argument I was putting is that both enthalpy (energy) of fusion and vapourisation are forms of potential energy arising from intermolecular forces, this is the conventional viewpoint and has been for a long time. Calling them (latent) heat of fusion or vapourisation introduces confusion between kinetic energy (heat) and potential energy. -- Damorbel ( talk) 07:30, 28 March 2013 (UTC)
Yes it's fascinating to note that we have this interrelationship between energy and temperature during the phase periods, and then the hiatus while the atom sorts out its internal energy storage (internal construction) problems. But heat energy is still matter (mass) times velocity squared whether you can see it or not. In the CRC handbook you have the Calorie defined in terms of their favorite energy unit the Joule as being 4.1868 joules. And the joule is 10 million ergs. So if you had a balloon with some water and you put heat in it and expanded it and if you were outside it and didn't have the buoyancy of the air and couldn't see its size change you wouldn't note it to be any different with all that additional heat energy. But since our concept of temperature is related to the heat energy mass times velocity squared/2 values, we soon get into astronomical temperature values when we get into the presumed velocities of the Big Bang theory. And at that level their value isn't telling us much of anything. WFPM ( talk) 17:41, 28 March 2013 (UTC)
The following sentence is wrong: " Heat ... is synonymous with heat flow and heat transfer." Heat is not synonymous with heat transfer. That statement is risible. I also commented on the talk page of the Heat Capacity article. "Freeman Dyson in [Scientific American 1954] writes: Heat is disordered energy." ← this is from my 1966 Physics textbook (Halliday & Resnick Pts I & II pg 640). Heat transfer is a process, heat is a type of energy. If someone wants to make an argument that the process is the thing, then they should do so explicitly, but NOT in the introduction. The logical problem I see in making this claim, is that multiple different processes in an isolated system can lead to identical heat energy transferred (but not identical final state, obviously). The process is not the (abstract) thing. 173.189.78.236 ( talk) 01:46, 18 May 2013 (UTC)
The observation by editor 173.189.78.236 that Heat is not synonymous with heat transfer is entirely correct, heat is measured in joules (J), heat transfer in joules per second (J/s). Only the truly ignorant could possibly see these as somehow "equivalent". I propose that the statement (and its consequences in the article) be deleted.
Similarly I am replacing my contribution, removed here by User Cburnett. My contribution drew attention to the fact that it is only the energy that is equivalent in thermodynamic systems; bundling kinetic and potential energy in the same category, which is what the " = " does, is a mathemamatical simplification of physics much too far, clearly leading tho the kind of confusion noted by editor 173.189.78.236. -- Damorbel ( talk) 06:20, 27 May 2013 (UTC)
Further to the statement:-
If heat is "not a type of energy", then just what is it?
Saying that it is "not a type of energy" cuts out most of physical existance (E = mc2) which is either a remarkable scientific breakthrough or plain absurd.
Such statements have no place whatsoever in Wikipedia. -- Damorbel ( talk) 07:07, 27 May 2013 (UTC)
This article cannot make a big point of distinguishing kw from kw hrs. Commercial electrity is discussed in both terms and so is heat. But we cannot push the analogy too far because while charge is conserved, heat is not. Thus , the total heat absorbed by an object need not be its heat content. The very idea of heat content, due to nonconservation, is a bad idea. As well speak of an object's work content as its heat content. "Thermal energy content" sounds better but is no more legitimate. "Thermal energy flow" is as silly as static electricy flow. There is no static thermal energy. And we already have a name for thermal energy flow: it's called "heat." S B H arris 18:05, 28 May 2013 (UTC)
Jheald has reversed my edit with the comment "WP has to reflect the position of the scientific community."
Since the article currently has:-
- which is not compatible with the fact that the energy content of matter is directly proportional to its absolute temperature, i.e. its heat; whereas Heat transfer is proportional to temperature difference, not to absolute temperature. These are quite different matters and a Wiki article should make this quite clear. -- Damorbel ( talk) 05:38, 29 May 2013 (UTC)
By directly proportional I do not mean linearly proportional.
True enough. But at 0K the heat is still zero joules. -- Damorbel ( talk) 18:03, 29 May 2013 (UTC)
Cardamon, the (current) opening statement of the article is:-
This is incorrect in all respects, e.g. heat is the property of a body that gives rise to chemical change.
Also you write:-
Please say:-
1/ Do you need a heat transfer causing temperature difference, to have "hotness"?
2/ Does a system at T > 0K in thermal equilibrium, thus without any heat transfer, contain any "heat"? -- Damorbel ( talk) 05:47, 31 May 2013 (UTC)
This reversal here explains:-
I do not think there is a consensus anywhere for heat flowing, this should have died in the 19th century. It is completely destroyed by the conservation of energy. I suggest that explanations relying on "heat flowing" be confined to historical articles about caloric. Caloric flowed, but heat doesn't. Let's get rid of this non-scientific idea! (I consider this discussion sufficient to eliminate the (linked) edit unless, of course, a good defense of caloric appears! -- Damorbel ( talk) 15:46, 17 July 2013 (UTC)
SBHarris you write
If heat flows it is conserved. But, for example, in the carnot cycle heat neither 'flows' nor is conserved, the output heat, at a lower temperature, is always less than the input heat. The work done by a (perfect) Carnot machine is equal to the difference between the input heat and the output heat, since the work done by the carnot machine has an mechanical energy equivalent to the heat difference, energy is conserved.
Similarly with 'ice melting'. When ice melts there is no change of the kinetic energy in the ice because there is no change of temperature. The energy of the H2O must increase to melt the ice but that is to break the crystal bonds of the ice. This energy of fusion can come from any source, chemical energy, mechanical work, there is no requirement for it to come from the kinetic energy of other particles i.e. heat. -- Damorbel ( talk) 06:17, 18 July 2013 (UTC)
Editor Harris, you write:-
I suggest that it is water that has more potential energy than ice, this is the so-called latent heat given up as it freezes.
And again you write:-
How can it "transfer... into the crystal"? Surely the crystal ceases to exist when it melts? It the fusion energy (latent heat of fusion) transferred to the the water molecules that puts them in the liquid state.
You have written nothing that supports deleting my edit; please explain why the deletion should stand. -- Damorbel ( talk) 07:15, 18 July 2013 (UTC)
Here This edit makes an already poor article worse, How is it possible to claim that:
That means that the law of conservation of energy is being explicitly ignored. Gentlemen please!
The article contains massive deficiencies e.g. why no mention the fact that heat energy is zero at 0K?
The article has other very serious deficiencies, throughout the whole article it constantly confuses heat with heat transfer (calling the latter "heat flow"!), at the very least it should specify the difference. -- Damorbel ( talk) 07:48, 18 July 2013 (UTC)
Um, Chjoaygame, (I suppose it is your contribution above) the conservation of energy and the non consevation of heat is not a private view. If you wish to promote the caloric theory, please do it in that article. Even the wiki article on the conservation of energy explains the origins how and why heat is not a conserved quantity, this is so important it should be prominent in the Wiki article on heat.
An article on a scientific matter needs to be clear, the fact that many authors do not understand that 'heat flow' is a dead concept is every reason why the error should be identified, it is absolutely equivalent to the old flat earth concept, mention it but please don't ever cite it as a valid scientific idea. -- Damorbel ( talk) 09:34, 18 July 2013 (UTC)
Damorbel has made two significant edits, one an undoing, the other an overwriting of the lead.
The undo is claimed by Damorbel to be justified by "unavailability" of one of the cited reliable sources, but which one is not stated by Damorbel. All the cited sources are standard texts available in libraries. Damorbel's claim of "inaccessibility" is not accurate, and in any case would be an inadequate reason to delete the whole new section.
The overwrite is an attempt by Damorbel to impose his private views against the accepted orthodoxy of current reliable sources, yet another of his repeated attempts of this kind. Moreover Damorbel's overwrite contains errors of physics which have been pointed out to Damorbel elsewhere, including just above by SBHarris, and it would be redundant for me to repeat those criticisms of his private views again here. Damorbel needs to take heed of those criticisms, not ignore them as his overwrite attempts to do. Damorbel's attempt to re-write the lead is not acceptable. Chjoaygame ( talk) 09:06, 18 July 2013 (UTC)
Your request for reasons is unfulfillable because it is based on a mistaken premise And what "mistaken premise" please? You do not identify any "mistaken premise", How am I supposed to respond?
As I have pointed out before, the article makes no distinction between heat as a form of energy (joules) and heat transfer which is joules per second (watts). This is not "a peculiarity of customary language", it equally deficient with failing to distinguish between distance (metres) and speed (metres per second) and I see nothing in the article or the talk that deals with this fundamental objection to how the article is written, the article is grossly in error. -- Damorbel ( talk) 11:28, 18 July 2013 (UTC)
It's silly to insist that heat be a kinetic thing when there are plenty of ways to transfer heat that aren't kinetic. Heat transferred as radiation isn't kinetic, and that's reason enough right here not to generalize. But also there are latent heat transfers from mechanisms like steam condensation, that transfer large amounts of heat in turbine systems, and that heat energy is stored as latent heat of vaporization, not kinetic energy of molecules. Clear? S B H arris 01:25, 19 July 2013 (UTC)
Why, both. The heat that leaves the water is the heat that enters the ice. Joules and watts of one is joules and watts of the other. To make or destroy heat you need a 3-D control VOLUME. A surface will never do. Just like electricity, where the analogy is close. Hope that's helpful, S B H arris 10:57, 19 July 2013 (UTC)
After that, however, all bets are off. The energy that crosses this surface is heat while it is in the act of crossing, but it is not (necessarily) entirely heat before, and it is not (necessarily) 100% heat after it has crossed. Heat is "conserved" while it crosses the surface inasmuch as the heat energy that leaves one volume is the same as the energy that enters the other. But after that, only the energy is conserved, as some of the heat can (and probably does) change forms to some sort of other energy that is non-thermal. Its "thermal-ness" (its nature) is not conserved when talking about the volumes it come from and goes to. Only when talking about the surface is the heat that leaves the water the same as the heat that enters the ice. After it has crossed, it is internal energy, but no longer need be heat (it CAN be heat in conduction, but there is no guarantee). And after it is past the surface it need not be any longer thermal energy, which is why we deprecate the term except at the 2-D boundary, through which heat flows. S B H arris 01:29, 20 July 2013 (UTC)
“ | Heat is energy proportional to the temperature(s) of the body. | ” |
— user:Damorbel |
Damorbel, could you specify a WP:reliable source that backs your claim about this proportionality (mathematics)? Incnis Mrsi ( talk) 14:48, 19 July 2013 (UTC)
I tire of correcting Damorbel's faulty edits. I trust someone else may find time to do it on his latest]. Part of the trouble is that responding to his errors only encourages him to make more of them. Chjoaygame ( talk) 13:49, 18 July 2013 (UTC)
I would like to have all details of these errors, please.
Your remark :-
Must be seen as a personal comment. Please refrain, your opinions about me are of no relevance in Wikipedia. -- Damorbel ( talk) 14:03, 18 July 2013 (UTC)
Damorbel, I will try not to make any personal comments here. If you don't stop re-inserting your views against the consensus here, we're going to have to ask admins to take action against you to prevent this. You keep re-inserting your incorrect statements about heat being kinetic energy, etc. It's good that you're interested in this subject but you should take thermodynamics course or read textbk if you want to find out how the scientific community defines these terms rather than how you are defining them. Or, please try reading the Heat article in another language as linked on the left side, using Google Translate to read it in English. Otherwise, there are other venues where you can write essays about why these terms should be (re)defined in the way you describe, but not in an encyclopedia, please. In case it helps you at all, let me point out that thermal energy is stored in part in the oscillations of molecules and atoms, and oscillations involve a continual transformation between kinetic energy (reaching a max when the particle is moving fastests) and potential energy (when the particle is at its most extreme displacement). Look up oscillations of springs for this concept. Thermal energy is a term used to describe a property of a system or body, while the term heat is defined as only a property of a specific process that transfers a given amount of energy in certain ways (which represents a change in energy of one system and opposite change in another). Also, Joules/second simply aren't units of energy (nor of heat), they're units of power (pls. look it up), which is energy per unit time.
DavRosen (
talk)
14:23, 18 July 2013 (UTC)
10:27, 18 July 2013 Damorbel (talk | contribs) . . (55,110 bytes) (-201) . . (Undid revision 564791172 by DavRosen (talk)DavRosen writes:- " Pls. take course or read textbk)" Personal attack!) updated since my last visit (undo | thank)
Damorbel, I meant it as a constructive suggestion for finding out the accepted definitions of some of these terms, but I can see how you could view it as a personal attack, and I apologize for that. That does not give you the right to continue your edit war: you have re-inserted your views on heat being kinetic energy, among others, many times, and they have been corrected by several different editors. The consensus here is clearly that your views are your own, and not encyclopedic descriptions of mainstream scientific usage. You can't keep putting your own views in -- you have to first obtain/change the consensus here on the Talk page. I, myself, am not going to undo your undo of my undo of your views because I don't want to be seen as edit-warring. I have only done that single edit (undo) of this article on this dispute. Maybe I'll just tag. DavRosen ( talk) 14:47, 18 July 2013 (UTC)
Damorbel, maybe it would help if you consider a solid rather than a gas. How can the thermal energy of a solid object (such as a piece of wood) be entirely kinetic when its molecules don't travel around? It has thermal degrees of freedom such as oscillation/vibration of those molecules, but the force keeping the molecules from traveling far is related the potential energy [gradient]. DavRosen ( talk) 14:59, 18 July 2013 (UTC)
DavRosen, you write:-
You are correct. But these vibrations are called ' degrees of freedom' where the potential and kinetic energy alternate, on average they are the same and each has a peak equal to twice its average, so the peak (of either kinetic or potential energy) is equal to the total energy content.
The concept of thermal energy does not involve any particular measure of temperature; two system have different thermal energies, but the same temperature - result no heat transfer. But if they have different temperatures but the same themal energy then there will be energy transfer (from the hotter to the colder.)
Finally. You write:-
That is what I meant when I insisted that heat transfer is measured in Watts (Joules per second) and heat (by itself) in Joules. -- Damorbel ( talk) 20:42, 18 July 2013 (UTC)
DavRosen, I wonder if you get what I am saying about the 'potential energy' in an oscillating system. I had the same problem with this my self, it is not well explained and probably not very well by me. I think Spiel496 was pointing this out in his note above. Whatever the case I would like to be sure it is understood.
Sorry if I was a bit sensitive about personal remarks but they are very much against Wiki policies. -- Damorbel ( talk) 20:50, 18 July 2013 (UTC)
Damorbel:
COMMENT: Now hold your horses. The above equation presumes Cp (heat capacity, constant pressure) is some kind of constant which doesn't change with temperature. How else could you multiply by twice the T and get twice the J? You can't. Cp(T) is a function of temperatue. If you want to know how much heat it takes to reach a certain temperature, this is an integration:
Where the limits of integration are from 0 K to your temperature T. And since the function Cp(T) changes in odd and tricky ways (including going to zero near absolute zero), the Q you get is impossible to simply calculate. C(T) has to be measured at each T. Worst of all, C is a function of constant volume or constant pressure. If you use C at constant pressure, your system will do PV work as it heats, and some heat will be transformed to work. It will therefore take more Q to reach a given T. It is also for this reason that we cannot speak of a certain Q "residing" in an object that has been warmed. We don't know how much work the object did on its suroundings by expansion, while warming. There are many says to get to the same volume and the same temperature for the same object, and each way absorbs a different amount of heat energy. Thus, there is no such thing as the "amount" of thermal energy "in" an object. S B H arris 06:19, 24 July 2013 (UTC)
Damorbel:
COMMENT: Needless to say, the above is all nonsense. Pay no attention to it. The idea that 2 moles of anything at half the temp T contains the same "thermal energy" as one mole at temp T, also assumes that heat capacity is some kind of constant. It isn't. S B H arris 06:24, 24 July 2013 (UTC)
-- Damorbel ( talk) 07:48, 23 July 2013 (UTC)
Robert McClenon, the kinetic energy in a mole of material is the sum of the energy in the degrees of freedom of the particles in the system, there are N = particles (N is Avogadro's constant) in a mole so the energy in a mole is E = kNT where k is the Boltzmann constant (The Boltzmann constant is the energy of one particle per unit temperature.)
This is much the same as the gas equation:-
where PV is the volumetric energy of the system.
Needless to say for solids and liquids PV is simply replaced by the
thermal energy E (joules) in the solid, and the above equation becomes:-
Sbharris comment:
Hold Horses The phrase "Needless to say" above, means you've just been fed much B.S. The equation PV = NkT holds for an ideal gas, and there the truth stops. Here the pressure is the pressure you get if N moles of the gas is held in a volume V. But what if you put N moles of a liquid or solid, into the same volume? Would it have the same pressure? No, it might not have any pressure. The PV
means nothing for a solid or liquid, because we don't know what P is, and it might be zero. So this Damorbel proposal to replace the PV for a gas, with the "thermal energy" of a solid or liquid with the same number of particles (moles) as that gas, is complete nonsense!! There is no reason to imagine tha tis true.
A solid or gas has no "volumetric energy." Its pressure may well be zero, so PV is zero, and what's the volumetric energy then? Nothing. S B H arris 06:19, 24 July 2013 (UTC)
Damorbel:
If, as above, the solid has N particles, then the thermal energy is the temperature
to be seen by rearranging equ.(2) :-
This is the temperature T because we have chosen N which means there is one mole of particles.
NB Please try to edit outside my arguments, you have put your contrib. right between the two points I am making above.
-- Damorbel ( talk) 13:14, 23 July 2013 (UTC)
Even in an ideal gas, the total kinetic energy E of the molecules in a gas is 3/2*RT, which is 3/2 NkT. But it is actually true that PV = nKT. Therefore, you can see that E (kinetic) = 3/2 PV. The total pressure*volume product of N moles of idea gas is not E (the kinetic energy of the molecules of the gas) but actually only 2/3 * E. Poor Damorbel is wrong about even ideal gases, which have 50% more kinetic energy in their molecules, than you would calculate by multiplying P times V. There actually is no connection between the PV product per particle of a gas, and the kinetic energy of that particle. They are not the same, only somewhat close to the same. If you used one to calculate the other, you'd be wrong by 50%.
The equation for the speed of an ideal gas molecule is v^2 = 3kT/m where m is the mass of the molecule. If Damorbel was right, that 3 would be a 2. But it's a 3. It's a shame, but there you are. Damborbel's entire argument rests on the idea that 3 = 2. And that's only the beginning of his error. S B H arris 06:19, 24 July 2013 (UTC)
where it says:-
Work by a gas
Where P is pressure, V is volume, and a and b are initial and final volumes.
Very nice, but the matter in hand is the energy of the gas particles, which is independent of the mass (mass = 'm' in your equation) I suggest that the ideal gas equation may be clarified if it is written like this:-
where :-
(This material is copied from the Gas laws article)
Looked at this way you can see the relationship of energy, the particle number N, energy per particle (E/N) and it also should be clear that a single particle has an (average) temperature.-- Damorbel ( talk) 07:55, 24 July 2013 (UTC)
gas laws article. The last part of the equation is there, but nothing article says that E = PV for an ideal gas. It is true that E = P(ΔV) when a gas is expanded or contracted by volume ΔV, all the time maintaing constand pressure P. But that's not the E (energy ) IN THE GAS. In that case, it's the energy that leaves the gas or enters the gas as the volume changes by ΔV. It surely does not imply that the kinetic energy of the gas molecules is PV for a volume of gas V. It is not, rather this energy is 3/2 * PV. The kinetic energy of an average gas molecule is 3/2 kT, not kT. Add them all up and you get E(total) = 3/2 NkT = 3/2 PV.
Perhaps you think that the kinetic energy of a gas molecule should be kT and not 3/2 kT. Too bad. In solids where half the energy is kinetic, the figure is 2 (3/2)kT = 3kT or 3RT per mole. Which is why the heat capacity dT/dQ of most solids approaches the Dulong-Petit limit of 3R per mole. S B H arris 03:32, 25 July 2013 (UTC)
These are the gas laws and kinetic theory and equations of state, available in Wikipedia, should be known to all thermodynamicists, but are available at NASA -- Damorbel ( talk) 16:06, 23 July 2013 (UTC)
Enric Naval, you write:-
Which of those pages makes the same chain of equations and reaches the same conclusions?
I'm afraid your question is unclear. I am not in the least satisfied with the state of the articles on Heat Temperature and Thermal energy so it is imposible to summarise how they mislead in the conclusions you might reach by reading them!
-- Damorbel ( talk) 17:38, 23 July 2013 (UTC)
Isn't what is measured in Joules per second actually heat flow rate or heat transfer rate? It is true that heat as used in thermodynamics is not a state variable but a signed quantity representing a transfer. My recollection is that what is non-technically thought of as heat is really enthalpy, which is a state variable that can be changed by a heat transfer. Robert McClenon ( talk) 00:47, 23 July 2013 (UTC)
Thanks for the tip, I have a terrible time with this! -- Damorbel ( talk) 13:37, 23 July 2013 (UTC)
I apologize for splitting Damorbel's post. I did that unintentionally. I was just very annoyed that he proposed changing the dimensionality of heat without citing a source. Robert McClenon ( talk) 23:57, 23 July 2013 (UTC)
![]() | This is an archive of past discussions. Do not edit the contents of this page. If you wish to start a new discussion or revive an old one, please do so on the current talk page. |
Archive 10 | ← | Archive 12 | Archive 13 | Archive 14 | Archive 15 | Archive 16 | → | Archive 20 |
I have 'undone' here [1]
It is a fact that the internal energy of an isolated system is conserved, that is why it is called isolated.
Whatever the 'law' says or requires or even demands, it does not govern the facts. -- Damorbel ( talk) 17:50, 6 February 2013 (UTC)
Suppose an isolated system was in a state of absolute motion. How would it know its (heat) condition of kinetic energy of motion? WFPM ( talk) 00:16, 6 March 2013 (UTC)
Since the common concept of heat is its association with 'hotness' or 'coldness' i.e. temperature, surely this should be explained in the opening section as well as the role of temperature difference? -- Damorbel ( talk) 16:45, 8 March 2013 (UTC)
Currently the article says:-
which makes heat independent of temperature, it would also make heat a conserved quantity. Would you care to confirm that this is what you mean? -- Damorbel ( talk) 21:27, 10 March 2013 (UTC)
If heat is not independent of temperature, why does the article, in the opening statement, say " Heat flow from hotter to colder systems occurs spontaneously, "? This statement makes the position (of the article) very clear, that heat is proportional to the difference in temperature, i.e. very clearly not a function of temperature. Is this correct? -- Damorbel ( talk) 06:48, 11 March 2013 (UTC)
There have been countless electrons spilt here on the definition of quantity of energy transferred as heat for this article. I hope I may be forgiven for saying some more about it. I have to say that I think my understanding has improved over the years. In particular I have to say I was partly mistaken in my strictures upon Count Iblis, and I would like to say I am sorry for the times when I went over the top. The matter is not one-sided. I made much of the idea that temperature has to be definable for heat to make sense. I would now speak more carefully. Count Iblis wrote: "Work doesn't have to be mechanical work. The work done by a system is defined as the decrease in the internal energy of a system due to the change of its external parameters." This is one way of seeing things. I would say that in the Carathéodory story, the decrease of internal energy of the system is defined as derived from the measured adiabatic work needed for the change of state. In the Gibbs story, one postulates directly the existence of the internal energy and doesn't derive it from work; of course still one can specialize to a closed system and then derive the work from the postulated internal energy.
I will now try here to say how I think quantity of energy transferred as heat should be defined here.
Quantity of energy transferred as heat is a term of thermodynamics that refers to a specified change of state of a closed system. The initial and final states of the system have defined temperatures and pressures. The quantity of energy transferred as heat is defined as a difference between two quantities of energy transferred as work. One of those quantities is the amount of adiabatic work needed to go between the initial and final state of the change; it refers to the specified change of state only through its initial and final states. The other is the amount of work done by the system on its surroundings during the specified change. This work is in general not adiabatic, and in general includes pressure-volume work and isochoric work. It depends only on the time course of the values of the external variables, including those such as the forces exerted by the surroundings on the walls of the system. How those forces are specified is important. If the work is mediated by a piston, then the external forces that determine the motion of the piston need to be defined. The piston may be driven by a rod. Then the force exerted by the rod on the piston must be specified. The external pressure on the external surface of the piston must also be specified throughout the course of the process, though it might be neglibly small. (I formerly insisted that if that pressure could not be defined during the course of the specified process, then the work could not be defined; that is true. Moreover I insisted that when that pressure was not defined, the external temperature was most likely also not defined. Therefore, I argued, when the external temperature was not defined, the work was not defined. I went too far there. It might sometimes be that the external pressure is defined while external temperature is not; still the work would be defined, as Count Iblis pointed out.) There is no requirement by definition that the external and internal temperatures and piston pressures be equal during the course of the process, but respectively they must be equal in the initial state and in the final state, which are respectively required by classical thermodynamics to be in thermal and mechanical equilibrium with the surroundings. Chjoaygame ( talk) 10:44, 12 March 2013 (UTC)
This edit proposes that a sentence about conduction, cited in the article, appears on page 1 of Partington 1949. In the copy I have here it appears on page 118, and not on page 1. Perhaps the creator of the edit would very kindly tell how he is accessing the source? Chjoaygame ( talk) 08:25, 13 March 2013 (UTC)
From the beginning paragraph "heat is energy transferred from one body to another by thermal interactions." Convection therefore is not a method of heat transfer as the heat is retained by the body and the body itself moved. Strictly speaking convection is a special form of conduction - conduction in a fluid. FlipC ( talk) 10:53, 14 March 2013 (UTC)
The Reif reference is to a textbook, so may well be unreliable. It's definition of heat is inconsistent in that it confuses heat and heat transfer. This is self contradictory, so not even wrong! -- Damorbel ( talk) 15:38, 23 March 2013 (UTC)
You write:-
One of the features that distinguishes heat from energy is that energy is a conserved quantity, whereas it is a fundamental aspect of modern physics is that heat is not a conserved quantity. Is this included in your questions " about the theory of heat "? -- Damorbel ( talk) 06:32, 27 March 2013 (UTC)
The temperature of a solid rises when energy is added, the rising temperature means that the atoms (or molecules) of the solid vibrate with increasing amplitude until, at a particular temperature, the (crystaline?) bonds holding it in solid form, begin to break, it is melting.
Continuing to add energy breaks more bonds without increasing the temperature as more of the solid melts. Finally the solid is completely melted and the temperature starts rising again, with the molecular motion of the liquid increasing further. The amount of energy needed to melt (fuse) a solid is properly called the enthalpy of fusion but is popularly (and mistakenly) called the latent heat of fusion.
From this you can see adding energy can either raise the temperature i.e. increase the heat, or melt the solid when its temperature does not rise. This is similar to boiling - energy is added to a boiling liquid without raising it's temperature; this energy is called the enthalpy of vaporization, often (improperly) called latent heat of vaporization.
Enthalpy is a more accurate term than latent heat because it represents potential energy, the energy of the bonds holding atoms or molecules together in a solid, whereas heat is, as you noted, the kinetic energy of atoms and molecules. -- Damorbel ( talk) 21:30, 27 March 2013 (UTC)
You write:-
Are you saying that this influences the relation of particle energy and temperature? If this was so there would be different Boltzmann constants for solids and liquids.
The argument I was putting is that both enthalpy (energy) of fusion and vapourisation are forms of potential energy arising from intermolecular forces, this is the conventional viewpoint and has been for a long time. Calling them (latent) heat of fusion or vapourisation introduces confusion between kinetic energy (heat) and potential energy. -- Damorbel ( talk) 07:30, 28 March 2013 (UTC)
Yes it's fascinating to note that we have this interrelationship between energy and temperature during the phase periods, and then the hiatus while the atom sorts out its internal energy storage (internal construction) problems. But heat energy is still matter (mass) times velocity squared whether you can see it or not. In the CRC handbook you have the Calorie defined in terms of their favorite energy unit the Joule as being 4.1868 joules. And the joule is 10 million ergs. So if you had a balloon with some water and you put heat in it and expanded it and if you were outside it and didn't have the buoyancy of the air and couldn't see its size change you wouldn't note it to be any different with all that additional heat energy. But since our concept of temperature is related to the heat energy mass times velocity squared/2 values, we soon get into astronomical temperature values when we get into the presumed velocities of the Big Bang theory. And at that level their value isn't telling us much of anything. WFPM ( talk) 17:41, 28 March 2013 (UTC)
The following sentence is wrong: " Heat ... is synonymous with heat flow and heat transfer." Heat is not synonymous with heat transfer. That statement is risible. I also commented on the talk page of the Heat Capacity article. "Freeman Dyson in [Scientific American 1954] writes: Heat is disordered energy." ← this is from my 1966 Physics textbook (Halliday & Resnick Pts I & II pg 640). Heat transfer is a process, heat is a type of energy. If someone wants to make an argument that the process is the thing, then they should do so explicitly, but NOT in the introduction. The logical problem I see in making this claim, is that multiple different processes in an isolated system can lead to identical heat energy transferred (but not identical final state, obviously). The process is not the (abstract) thing. 173.189.78.236 ( talk) 01:46, 18 May 2013 (UTC)
The observation by editor 173.189.78.236 that Heat is not synonymous with heat transfer is entirely correct, heat is measured in joules (J), heat transfer in joules per second (J/s). Only the truly ignorant could possibly see these as somehow "equivalent". I propose that the statement (and its consequences in the article) be deleted.
Similarly I am replacing my contribution, removed here by User Cburnett. My contribution drew attention to the fact that it is only the energy that is equivalent in thermodynamic systems; bundling kinetic and potential energy in the same category, which is what the " = " does, is a mathemamatical simplification of physics much too far, clearly leading tho the kind of confusion noted by editor 173.189.78.236. -- Damorbel ( talk) 06:20, 27 May 2013 (UTC)
Further to the statement:-
If heat is "not a type of energy", then just what is it?
Saying that it is "not a type of energy" cuts out most of physical existance (E = mc2) which is either a remarkable scientific breakthrough or plain absurd.
Such statements have no place whatsoever in Wikipedia. -- Damorbel ( talk) 07:07, 27 May 2013 (UTC)
This article cannot make a big point of distinguishing kw from kw hrs. Commercial electrity is discussed in both terms and so is heat. But we cannot push the analogy too far because while charge is conserved, heat is not. Thus , the total heat absorbed by an object need not be its heat content. The very idea of heat content, due to nonconservation, is a bad idea. As well speak of an object's work content as its heat content. "Thermal energy content" sounds better but is no more legitimate. "Thermal energy flow" is as silly as static electricy flow. There is no static thermal energy. And we already have a name for thermal energy flow: it's called "heat." S B H arris 18:05, 28 May 2013 (UTC)
Jheald has reversed my edit with the comment "WP has to reflect the position of the scientific community."
Since the article currently has:-
- which is not compatible with the fact that the energy content of matter is directly proportional to its absolute temperature, i.e. its heat; whereas Heat transfer is proportional to temperature difference, not to absolute temperature. These are quite different matters and a Wiki article should make this quite clear. -- Damorbel ( talk) 05:38, 29 May 2013 (UTC)
By directly proportional I do not mean linearly proportional.
True enough. But at 0K the heat is still zero joules. -- Damorbel ( talk) 18:03, 29 May 2013 (UTC)
Cardamon, the (current) opening statement of the article is:-
This is incorrect in all respects, e.g. heat is the property of a body that gives rise to chemical change.
Also you write:-
Please say:-
1/ Do you need a heat transfer causing temperature difference, to have "hotness"?
2/ Does a system at T > 0K in thermal equilibrium, thus without any heat transfer, contain any "heat"? -- Damorbel ( talk) 05:47, 31 May 2013 (UTC)
This reversal here explains:-
I do not think there is a consensus anywhere for heat flowing, this should have died in the 19th century. It is completely destroyed by the conservation of energy. I suggest that explanations relying on "heat flowing" be confined to historical articles about caloric. Caloric flowed, but heat doesn't. Let's get rid of this non-scientific idea! (I consider this discussion sufficient to eliminate the (linked) edit unless, of course, a good defense of caloric appears! -- Damorbel ( talk) 15:46, 17 July 2013 (UTC)
SBHarris you write
If heat flows it is conserved. But, for example, in the carnot cycle heat neither 'flows' nor is conserved, the output heat, at a lower temperature, is always less than the input heat. The work done by a (perfect) Carnot machine is equal to the difference between the input heat and the output heat, since the work done by the carnot machine has an mechanical energy equivalent to the heat difference, energy is conserved.
Similarly with 'ice melting'. When ice melts there is no change of the kinetic energy in the ice because there is no change of temperature. The energy of the H2O must increase to melt the ice but that is to break the crystal bonds of the ice. This energy of fusion can come from any source, chemical energy, mechanical work, there is no requirement for it to come from the kinetic energy of other particles i.e. heat. -- Damorbel ( talk) 06:17, 18 July 2013 (UTC)
Editor Harris, you write:-
I suggest that it is water that has more potential energy than ice, this is the so-called latent heat given up as it freezes.
And again you write:-
How can it "transfer... into the crystal"? Surely the crystal ceases to exist when it melts? It the fusion energy (latent heat of fusion) transferred to the the water molecules that puts them in the liquid state.
You have written nothing that supports deleting my edit; please explain why the deletion should stand. -- Damorbel ( talk) 07:15, 18 July 2013 (UTC)
Here This edit makes an already poor article worse, How is it possible to claim that:
That means that the law of conservation of energy is being explicitly ignored. Gentlemen please!
The article contains massive deficiencies e.g. why no mention the fact that heat energy is zero at 0K?
The article has other very serious deficiencies, throughout the whole article it constantly confuses heat with heat transfer (calling the latter "heat flow"!), at the very least it should specify the difference. -- Damorbel ( talk) 07:48, 18 July 2013 (UTC)
Um, Chjoaygame, (I suppose it is your contribution above) the conservation of energy and the non consevation of heat is not a private view. If you wish to promote the caloric theory, please do it in that article. Even the wiki article on the conservation of energy explains the origins how and why heat is not a conserved quantity, this is so important it should be prominent in the Wiki article on heat.
An article on a scientific matter needs to be clear, the fact that many authors do not understand that 'heat flow' is a dead concept is every reason why the error should be identified, it is absolutely equivalent to the old flat earth concept, mention it but please don't ever cite it as a valid scientific idea. -- Damorbel ( talk) 09:34, 18 July 2013 (UTC)
Damorbel has made two significant edits, one an undoing, the other an overwriting of the lead.
The undo is claimed by Damorbel to be justified by "unavailability" of one of the cited reliable sources, but which one is not stated by Damorbel. All the cited sources are standard texts available in libraries. Damorbel's claim of "inaccessibility" is not accurate, and in any case would be an inadequate reason to delete the whole new section.
The overwrite is an attempt by Damorbel to impose his private views against the accepted orthodoxy of current reliable sources, yet another of his repeated attempts of this kind. Moreover Damorbel's overwrite contains errors of physics which have been pointed out to Damorbel elsewhere, including just above by SBHarris, and it would be redundant for me to repeat those criticisms of his private views again here. Damorbel needs to take heed of those criticisms, not ignore them as his overwrite attempts to do. Damorbel's attempt to re-write the lead is not acceptable. Chjoaygame ( talk) 09:06, 18 July 2013 (UTC)
Your request for reasons is unfulfillable because it is based on a mistaken premise And what "mistaken premise" please? You do not identify any "mistaken premise", How am I supposed to respond?
As I have pointed out before, the article makes no distinction between heat as a form of energy (joules) and heat transfer which is joules per second (watts). This is not "a peculiarity of customary language", it equally deficient with failing to distinguish between distance (metres) and speed (metres per second) and I see nothing in the article or the talk that deals with this fundamental objection to how the article is written, the article is grossly in error. -- Damorbel ( talk) 11:28, 18 July 2013 (UTC)
It's silly to insist that heat be a kinetic thing when there are plenty of ways to transfer heat that aren't kinetic. Heat transferred as radiation isn't kinetic, and that's reason enough right here not to generalize. But also there are latent heat transfers from mechanisms like steam condensation, that transfer large amounts of heat in turbine systems, and that heat energy is stored as latent heat of vaporization, not kinetic energy of molecules. Clear? S B H arris 01:25, 19 July 2013 (UTC)
Why, both. The heat that leaves the water is the heat that enters the ice. Joules and watts of one is joules and watts of the other. To make or destroy heat you need a 3-D control VOLUME. A surface will never do. Just like electricity, where the analogy is close. Hope that's helpful, S B H arris 10:57, 19 July 2013 (UTC)
After that, however, all bets are off. The energy that crosses this surface is heat while it is in the act of crossing, but it is not (necessarily) entirely heat before, and it is not (necessarily) 100% heat after it has crossed. Heat is "conserved" while it crosses the surface inasmuch as the heat energy that leaves one volume is the same as the energy that enters the other. But after that, only the energy is conserved, as some of the heat can (and probably does) change forms to some sort of other energy that is non-thermal. Its "thermal-ness" (its nature) is not conserved when talking about the volumes it come from and goes to. Only when talking about the surface is the heat that leaves the water the same as the heat that enters the ice. After it has crossed, it is internal energy, but no longer need be heat (it CAN be heat in conduction, but there is no guarantee). And after it is past the surface it need not be any longer thermal energy, which is why we deprecate the term except at the 2-D boundary, through which heat flows. S B H arris 01:29, 20 July 2013 (UTC)
“ | Heat is energy proportional to the temperature(s) of the body. | ” |
— user:Damorbel |
Damorbel, could you specify a WP:reliable source that backs your claim about this proportionality (mathematics)? Incnis Mrsi ( talk) 14:48, 19 July 2013 (UTC)
I tire of correcting Damorbel's faulty edits. I trust someone else may find time to do it on his latest]. Part of the trouble is that responding to his errors only encourages him to make more of them. Chjoaygame ( talk) 13:49, 18 July 2013 (UTC)
I would like to have all details of these errors, please.
Your remark :-
Must be seen as a personal comment. Please refrain, your opinions about me are of no relevance in Wikipedia. -- Damorbel ( talk) 14:03, 18 July 2013 (UTC)
Damorbel, I will try not to make any personal comments here. If you don't stop re-inserting your views against the consensus here, we're going to have to ask admins to take action against you to prevent this. You keep re-inserting your incorrect statements about heat being kinetic energy, etc. It's good that you're interested in this subject but you should take thermodynamics course or read textbk if you want to find out how the scientific community defines these terms rather than how you are defining them. Or, please try reading the Heat article in another language as linked on the left side, using Google Translate to read it in English. Otherwise, there are other venues where you can write essays about why these terms should be (re)defined in the way you describe, but not in an encyclopedia, please. In case it helps you at all, let me point out that thermal energy is stored in part in the oscillations of molecules and atoms, and oscillations involve a continual transformation between kinetic energy (reaching a max when the particle is moving fastests) and potential energy (when the particle is at its most extreme displacement). Look up oscillations of springs for this concept. Thermal energy is a term used to describe a property of a system or body, while the term heat is defined as only a property of a specific process that transfers a given amount of energy in certain ways (which represents a change in energy of one system and opposite change in another). Also, Joules/second simply aren't units of energy (nor of heat), they're units of power (pls. look it up), which is energy per unit time.
DavRosen (
talk)
14:23, 18 July 2013 (UTC)
10:27, 18 July 2013 Damorbel (talk | contribs) . . (55,110 bytes) (-201) . . (Undid revision 564791172 by DavRosen (talk)DavRosen writes:- " Pls. take course or read textbk)" Personal attack!) updated since my last visit (undo | thank)
Damorbel, I meant it as a constructive suggestion for finding out the accepted definitions of some of these terms, but I can see how you could view it as a personal attack, and I apologize for that. That does not give you the right to continue your edit war: you have re-inserted your views on heat being kinetic energy, among others, many times, and they have been corrected by several different editors. The consensus here is clearly that your views are your own, and not encyclopedic descriptions of mainstream scientific usage. You can't keep putting your own views in -- you have to first obtain/change the consensus here on the Talk page. I, myself, am not going to undo your undo of my undo of your views because I don't want to be seen as edit-warring. I have only done that single edit (undo) of this article on this dispute. Maybe I'll just tag. DavRosen ( talk) 14:47, 18 July 2013 (UTC)
Damorbel, maybe it would help if you consider a solid rather than a gas. How can the thermal energy of a solid object (such as a piece of wood) be entirely kinetic when its molecules don't travel around? It has thermal degrees of freedom such as oscillation/vibration of those molecules, but the force keeping the molecules from traveling far is related the potential energy [gradient]. DavRosen ( talk) 14:59, 18 July 2013 (UTC)
DavRosen, you write:-
You are correct. But these vibrations are called ' degrees of freedom' where the potential and kinetic energy alternate, on average they are the same and each has a peak equal to twice its average, so the peak (of either kinetic or potential energy) is equal to the total energy content.
The concept of thermal energy does not involve any particular measure of temperature; two system have different thermal energies, but the same temperature - result no heat transfer. But if they have different temperatures but the same themal energy then there will be energy transfer (from the hotter to the colder.)
Finally. You write:-
That is what I meant when I insisted that heat transfer is measured in Watts (Joules per second) and heat (by itself) in Joules. -- Damorbel ( talk) 20:42, 18 July 2013 (UTC)
DavRosen, I wonder if you get what I am saying about the 'potential energy' in an oscillating system. I had the same problem with this my self, it is not well explained and probably not very well by me. I think Spiel496 was pointing this out in his note above. Whatever the case I would like to be sure it is understood.
Sorry if I was a bit sensitive about personal remarks but they are very much against Wiki policies. -- Damorbel ( talk) 20:50, 18 July 2013 (UTC)
Damorbel:
COMMENT: Now hold your horses. The above equation presumes Cp (heat capacity, constant pressure) is some kind of constant which doesn't change with temperature. How else could you multiply by twice the T and get twice the J? You can't. Cp(T) is a function of temperatue. If you want to know how much heat it takes to reach a certain temperature, this is an integration:
Where the limits of integration are from 0 K to your temperature T. And since the function Cp(T) changes in odd and tricky ways (including going to zero near absolute zero), the Q you get is impossible to simply calculate. C(T) has to be measured at each T. Worst of all, C is a function of constant volume or constant pressure. If you use C at constant pressure, your system will do PV work as it heats, and some heat will be transformed to work. It will therefore take more Q to reach a given T. It is also for this reason that we cannot speak of a certain Q "residing" in an object that has been warmed. We don't know how much work the object did on its suroundings by expansion, while warming. There are many says to get to the same volume and the same temperature for the same object, and each way absorbs a different amount of heat energy. Thus, there is no such thing as the "amount" of thermal energy "in" an object. S B H arris 06:19, 24 July 2013 (UTC)
Damorbel:
COMMENT: Needless to say, the above is all nonsense. Pay no attention to it. The idea that 2 moles of anything at half the temp T contains the same "thermal energy" as one mole at temp T, also assumes that heat capacity is some kind of constant. It isn't. S B H arris 06:24, 24 July 2013 (UTC)
-- Damorbel ( talk) 07:48, 23 July 2013 (UTC)
Robert McClenon, the kinetic energy in a mole of material is the sum of the energy in the degrees of freedom of the particles in the system, there are N = particles (N is Avogadro's constant) in a mole so the energy in a mole is E = kNT where k is the Boltzmann constant (The Boltzmann constant is the energy of one particle per unit temperature.)
This is much the same as the gas equation:-
where PV is the volumetric energy of the system.
Needless to say for solids and liquids PV is simply replaced by the
thermal energy E (joules) in the solid, and the above equation becomes:-
Sbharris comment:
Hold Horses The phrase "Needless to say" above, means you've just been fed much B.S. The equation PV = NkT holds for an ideal gas, and there the truth stops. Here the pressure is the pressure you get if N moles of the gas is held in a volume V. But what if you put N moles of a liquid or solid, into the same volume? Would it have the same pressure? No, it might not have any pressure. The PV
means nothing for a solid or liquid, because we don't know what P is, and it might be zero. So this Damorbel proposal to replace the PV for a gas, with the "thermal energy" of a solid or liquid with the same number of particles (moles) as that gas, is complete nonsense!! There is no reason to imagine tha tis true.
A solid or gas has no "volumetric energy." Its pressure may well be zero, so PV is zero, and what's the volumetric energy then? Nothing. S B H arris 06:19, 24 July 2013 (UTC)
Damorbel:
If, as above, the solid has N particles, then the thermal energy is the temperature
to be seen by rearranging equ.(2) :-
This is the temperature T because we have chosen N which means there is one mole of particles.
NB Please try to edit outside my arguments, you have put your contrib. right between the two points I am making above.
-- Damorbel ( talk) 13:14, 23 July 2013 (UTC)
Even in an ideal gas, the total kinetic energy E of the molecules in a gas is 3/2*RT, which is 3/2 NkT. But it is actually true that PV = nKT. Therefore, you can see that E (kinetic) = 3/2 PV. The total pressure*volume product of N moles of idea gas is not E (the kinetic energy of the molecules of the gas) but actually only 2/3 * E. Poor Damorbel is wrong about even ideal gases, which have 50% more kinetic energy in their molecules, than you would calculate by multiplying P times V. There actually is no connection between the PV product per particle of a gas, and the kinetic energy of that particle. They are not the same, only somewhat close to the same. If you used one to calculate the other, you'd be wrong by 50%.
The equation for the speed of an ideal gas molecule is v^2 = 3kT/m where m is the mass of the molecule. If Damorbel was right, that 3 would be a 2. But it's a 3. It's a shame, but there you are. Damborbel's entire argument rests on the idea that 3 = 2. And that's only the beginning of his error. S B H arris 06:19, 24 July 2013 (UTC)
where it says:-
Work by a gas
Where P is pressure, V is volume, and a and b are initial and final volumes.
Very nice, but the matter in hand is the energy of the gas particles, which is independent of the mass (mass = 'm' in your equation) I suggest that the ideal gas equation may be clarified if it is written like this:-
where :-
(This material is copied from the Gas laws article)
Looked at this way you can see the relationship of energy, the particle number N, energy per particle (E/N) and it also should be clear that a single particle has an (average) temperature.-- Damorbel ( talk) 07:55, 24 July 2013 (UTC)
gas laws article. The last part of the equation is there, but nothing article says that E = PV for an ideal gas. It is true that E = P(ΔV) when a gas is expanded or contracted by volume ΔV, all the time maintaing constand pressure P. But that's not the E (energy ) IN THE GAS. In that case, it's the energy that leaves the gas or enters the gas as the volume changes by ΔV. It surely does not imply that the kinetic energy of the gas molecules is PV for a volume of gas V. It is not, rather this energy is 3/2 * PV. The kinetic energy of an average gas molecule is 3/2 kT, not kT. Add them all up and you get E(total) = 3/2 NkT = 3/2 PV.
Perhaps you think that the kinetic energy of a gas molecule should be kT and not 3/2 kT. Too bad. In solids where half the energy is kinetic, the figure is 2 (3/2)kT = 3kT or 3RT per mole. Which is why the heat capacity dT/dQ of most solids approaches the Dulong-Petit limit of 3R per mole. S B H arris 03:32, 25 July 2013 (UTC)
These are the gas laws and kinetic theory and equations of state, available in Wikipedia, should be known to all thermodynamicists, but are available at NASA -- Damorbel ( talk) 16:06, 23 July 2013 (UTC)
Enric Naval, you write:-
Which of those pages makes the same chain of equations and reaches the same conclusions?
I'm afraid your question is unclear. I am not in the least satisfied with the state of the articles on Heat Temperature and Thermal energy so it is imposible to summarise how they mislead in the conclusions you might reach by reading them!
-- Damorbel ( talk) 17:38, 23 July 2013 (UTC)
Isn't what is measured in Joules per second actually heat flow rate or heat transfer rate? It is true that heat as used in thermodynamics is not a state variable but a signed quantity representing a transfer. My recollection is that what is non-technically thought of as heat is really enthalpy, which is a state variable that can be changed by a heat transfer. Robert McClenon ( talk) 00:47, 23 July 2013 (UTC)
Thanks for the tip, I have a terrible time with this! -- Damorbel ( talk) 13:37, 23 July 2013 (UTC)
I apologize for splitting Damorbel's post. I did that unintentionally. I was just very annoyed that he proposed changing the dimensionality of heat without citing a source. Robert McClenon ( talk) 23:57, 23 July 2013 (UTC)