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- Dear editor JoKalliauer, thank you for your post https://en.wikipedia.org/w/index.php?title=Talk%3AInternal_energy&type=revision&diff=1105103345&oldid=1104984019 on the talk page of the article on internal energy. Perhaps you may like to talk a bit with me on my talk page. I will shortly start a section, headed 'Thermodynamics', there for the purpose.Chjoaygame (talk) 20:11, 18 August 2022 (UTC)
- That you asked the question "Did I say something wrong?" suggested a good prospect for progress through a quiet cooperative chat.Chjoaygame (talk) 16:30, 25 August 2022 (UTC)
Dear JoKalliauer, it is good that you take an interest in this topic, but it is not good that you confound it with a different topic. I am sorry I was preoccupied and did not get around to talking over this matter with you last time.
What you like to call "thermal energy (i.e. internal kinetic energy)" is not a thermodynamic concept. It is a concept of statistical mechanics or of thermal physics. It leads students to be confused if the topics are not clearly distinguished.
The topic of the article is internal energy in thermodynamics. Statistical mechanics can in some cases (e.g. an ideal gas) give a detailed explanation of the distinction between the potential energies of relation between the microscopic particles of a body of matter and their kinetic energies, but, in many other cases, this is hardly feasible in practical detail. One of the great merits of thermodynamics is that it thoroughly abjures any attempt to make the distinction explicit. This is part of why Einstein said of thermodynamics that it is the only branch of physics that, within its domain of applicability, will never be overthrown. Thermodynamics is essentially a macroscopic account, with no reliance on microscopic ingredients. Statistical mechanics is essentially a microscopic account, with reference to thermodynamical quantities, but not taking them as leading ingredients. Physics in some parts of the world passed through a time when people thought that they would be very clever and combine thermodynamics with statistical mechanics in a 'modern and enlightened' topic called 'thermal physics'. Some people still like to think that way. But that way robs thermodynamics of its pristine logic and clarity, so that students exposed to that way miss the logical elegance of thermodynamics. Your "thermal energy (i.e. internal kinetic energy)" belongs not to thermodynamics itself, but to the statistical mechanical explanation of thermodynamics, and it is mentioned as doing so later in the lead of the article: "In statistical mechanics, the internal energy of a body can be analyzed microscopically in terms of the kinetic energies of microscopic motion of the system's particles from translations, rotations, and vibrations, and of the potential energies associated with microscopic forces, including chemical bonds." I think it would tend to confuse students and newcomers to find it also referred to earlier in the lead, in the part directly about thermodynamics.
I have not tried to undo your edit https://en.wikipedia.org/w/index.php?title=Internal_energy&diff=1134066890&oldid=1133471302 that puts it in again early in the lead: "... , but it includes the thermal energy (i.e. internal kinetic energy)". I hope you may be willing to undo it yourself. I would like to chat it over further with you if you like, either here or on my talk page, as you may please. I want to avoid a cycle of counter-edits, because it can lead to a mess, especially if it leads to a debate with too many participants on the talk page of the article.For the present, I have retired from editing the article on Heat because it has been taken over by drive-by shooters and instant experts who know everything and so do not need to read or understand the reliable sources, and indeed do not distinguish reliable sources from literary ones. The lead of the article on heat is now wrong and has been practically destroyed as a contribution to a logically structured development of thermodynamics, but I fear that attempts to fix it right now are likely merely to make the instant experts double down.Chjoaygame (talk) 05:04, 17 January 2023 (UTC)
- The Grand_canonical_ensemble uses the Grand_potential which is a function of Internal_energy, see Grand_potential#Definition. Either you slit Internal_energy into Internal_energy (macroscopic) and Internal_energy (microscopic), or you include both topics in this article. But just because you are familiar to only one of them, does not mean the other one is unimportant. — Johannes Kalliauer - contrib. 17:34, 17 January 2023 (UTC)
The total energy of a body is the sum of several components. Let denote the potential energy of the body as a whole, with respect to external fields, its kinetic energy as a whole relative to its surroundings, and its internal energy. Then its total energy is given by
- @Chjoaygame: Sorry K is only the "external kinetik energy"!
- Increasing the temperature increases the internal kinetic energy, and therfore also the internal energy.
- — Johannes Kalliauer - contrib. 17:35, 17 January 2023 (UTC)
Thank you for your thoughtful replies.
Of course you are right that increasing the temperature by heating the body increases the kinetic energies of the particles, without increasing the kinetic energy of the body as a whole with respect to its surroundings. Your term "external kinetic energy" is not often found in reliable sources on thermodynamics, and not even in reliable sources on statistical mechanics. The temperature is defined with respect to the body, as practically stationary, as distinct from its surroundings and external fields, with respect to which it is positioned and might move.
Of course you are right that the grand canonical ensemble is defined in terms of the grand potential which is defined in terms of the internal energy.
You prefer to start from the viewpoint of statistical mechanics, or of thermal physics, not from the viewpoint of thermodynamics. The grand canonical ensemble is a concept of statistical mechanics, microscopic in character, not of thermodynamics, macroscopic in character. The present article starts "The internal energy of a thermodynamic system ...". The present article is mainly structured from the viewpoint of thermodynamics, with explanations and analysis in terms of statistical mechanics: "In statistical mechanics, the internal energy of a body can be analyzed microscopically in terms of the kinetic energies of microscopic motion of the system's particles from translations, rotations, and vibrations, and of the potential energies associated with microscopic forces, including chemical bonds."
You write "But just because you are familiar to only one of them, does not mean the other one is unimportant." No one is suggesting that one of the viewpoints is unimportant. But the article distinguishes between the viewpoints. In the article lead, this is done by putting them in separate paragraphs. The kinetic energy of the particles, relative to the body as distinct from relative to the surroundings, is respected in the lead's third paragraph about the statistical mechanical analysis of the internal energy.For a body of matter such as a liquid or solid, the microscopic particles such as molecules are mostly not freely moving, but are subject to forces of intermolecular interaction, except that some electrons can be more or less freely moving. This is different from a body of matter such as an ideal gas, in which all the microscopic particles are more or less freely moving except during collisions. For a Knudsen gas, the particles are mostly freely moving, but the intermolecular collisions are rare, and it is common enough in nature to find departures from internal thermodynamic equilibrium, for example when the body is subject to time-invariant non-isotropic external radiation. The concept of 'thermal energy' is mainly concerned with cases in which there are many particles that are more or less freely moving, with frequent enough collisions, so that their kinetic energy is practically proportional to the temperature. That is why the SI temperature is no longer defined in thermodynamic terms. It is nowadays necessary to distinguish between thermodynamic temperature, defined macroscopically as Kelvin defined it, and SI temperature as currently defined by international convention in terms of microscopically explained properties. The reason is that some quantities governed by average particle kinetic energy can be measured more precisely than is practical for thermodynamic quantities.Chjoaygame (talk) 21:19, 17 January 2023 (UTC)
- @Chjoaygame: You write “It excludes the kinetic energy of the system as a whole”, this is pretty vage. Do you mean the kinetic energy of the center of mass of the system, or the movement of the boundary of the system? Because the center of mass can change without changing the position of the boundaries. — Johannes Kalliauer - contrib. 21:36, 17 January 2023 (UTC)
Thank you for your thoughtful post.
The kinetic energy of the system as a whole is the sum of the kinetic energies of its microscopic constituents considered as moving with respect to its surroundings, less the sum of the kinetic energies of its microscopic constituents considered as moving with respect to the system itself, defined its centre of mass considered as moving with respect to its surroundings. It is part of the definition of a thermodynamic system that it is in its own state of internal thermodynamic equilibrium.Chjoaygame (talk) 22:34, 17 January 2023 (UTC)
- @Chjoaygame: Let’s assume a box that is held in place to all surroundings (i.e. the earth stops spinning and just stays in place). That means if you have a closed box (e.g. a closed insulated bottle) not interacting with the surrounding in a gravitational field, and the orignially mixed liquid inside seperates into the heavy substances at the bottom and the lighter substances at the top, the center of mass moves with respec to its surroundings, but the box stays in place. So the seperation in the box creates a kinetic energy of the system as a whole, even though the box is not moving at all? — Johannes Kalliauer - contrib. 01:25, 18 January 2023 (UTC)
Thank you for your thinking this over.
- @Chjoaygame: How says that? As soon as you change temperature or preasure or a chemical reaction is going on, it won’t be in a state of internal thermodynamic equilibrium, that’s why we have wind within a closed system (e.g. earth). — Johannes Kalliauer - contrib. 02:22, 18 January 2023 (UTC)
7.900 bytes comment of Chjoaygame
Dear JoKalliauer, I get the impression that you are thinking this out for yourself, from scratch. That is commendable, and, in my opinion practically necessary, but, for the purpose of Wikipedia editing, it should be brought to completion by checks in reliable sources. This particular matter is not too easy to cover with brief explicit quotes from reliable sources.Chjoaygame (talk) 07:44, 18 January 2023 (UTC)
Again, Uffink writes:
People dispute whether one should in English speak of 'the minus oneth law of thermodynamics', or of the 'minus first law of thermodynamics'. I prefer to speak of 'the minus oneth'. I don't know what is the conventional preference. I am inclined to pronounce 'oneth' with a silent 'e' as in the dot in 'mon·th' and in 'ten·th'. The pronunciation may not matter too much.
Not too many texts, or even journal articles, talk of the 'minus oneth law of thermodynamics', though a few do. But reliable sources on thermodynamics take it for granted that a thermodynamic system is not just any macroscopic physical system. This is necessary for thermodynamics because the definition of thermodynamic entropy assumes that the system is in its own state of internal thermodynamic equilibrium. E.T. Jaynes writes:
Sorry to say I am ignorant of the German language. So I have to quote the English translation of Planck's Treatise. Having started with what is often called 'the zeroth law of thermodynamics', which had long before been stated by Maxwell, Plank goes on to write:
Planck does not name this as a law of thermodynamics. It is just his presupposition.
Bailyn expresses the minus oneth law as follows:
Callen is reliable source on basic thermodynamics, but he does not stick to the customary formulation of the customary axioms. He gives a long discussion of the state of thermodynamic equilbrium in a body. He expresses the minus oneth law as follows:
Brown & Uffink (2001) write the minus oneth law as follows:
Marsland, Brown, and Valente (2015) use the term 'minus first law' as follows:
You write "... a closed system (e.g. earth)." For many purposes, the earth is considered as an open system. For example, many hydrogen molecules in the atmosphere attain escape velocity and leave the earth, presumably for ever. The volcanic eruption near Tonga, mainly on 15 Jan 2023, is said to have ejected substantial amounts of matter into outer space. Meteors and meteorites, sometimes large ones, come into the earth system. Climate change debates are largely about how radiant heat from the sun is absorbed mainly as visible light and how infrared energy is radiated to space, largely from the atmosphere including clouds, but also to some extent through the atmospheric window from the condensed matter of the land and sea. Let alone being a closed system, the earth is not a thermodynamic system, because it is not in a state of its own internal thermodynamic equilibrium. The earth may be considered as a physical system, but not as a thermodynamic system.
@Chjoaygame: Thanks for writing a 7.900 bytes comment. Maybe there should exist two articles one about Internal energy (thermodynamics) and one about Internal energy (statistical ensemble). As long as Grand_potential#Definition links to Internal energy, Internal energy has to cover both topics. — Johannes Kalliauer - contrib. 17:59, 18 January 2023 (UTC)
The physical substance here is the distinction between a body of matter in its own state of internal thermodynamic equilibrium, and a system that is not so. Both the thermodynamic system and the ensembles of statistical mechanics refer to one and the same physical state of internal thermodynamic equilibrium, for which they assume the existence of a properly defined entropy.
The difference between thermodynamic equilibrium and non-equilibrium isn't just a difference of ball parks, nor a difference of planets, nor of solar systems: it's a difference of galaxies. For a non-equilibrium system, hardly anyone even tries to talk about giving a proper definition of entropy.Chjoaygame (talk) 21:35, 18 January 2023 (UTC)