![]() | 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 1 | Archive 2 | Archive 3 | Archive 4 | Archive 5 | Archive 6 |
1/ Opening paragraph - replace 'warm' with 'warmer' & 'hot' with 'hotter' (temperature is relative (2nd Law))
2/ 2nd paragraph has nothing to do with temperature per se and everything to do with a thermometer, i.e. how to measure it. To clarify, temperature as a measure of the concentration of thermal energy, temperature exists independently of however many systems are defined by the observer!
3/ 3rd (see 2/ above) should indicate very clearly that scales of temperature are there purely for the convenience of the observer and can be defined in any convenient way.
4/ 4th paragraph has no place in an introduction. Cleaned up, it might have a place under a section called 'History' which is yet to be written!
5/ 5th para. is completely confused, e.g. the first phrase "Microscopically, temperature determines the statistical distribution and the mean value of energy of motion" - not remotely true, check Maxwell-Boltzmann statistics or Maxwell-Boltzmann distribution (why on earth are there two articles for this in Wikipedia?) Microsopicaly means 'at the smallest possible subdivision', which is a 'degree of freedom' in this instance.
6/ 6th para. Much the same as the 5th. It refers to Thermal energy which redirects to Internal energy which opens with "internal energy is the total energy contained by a thermodynamic system" together with a reference to an article on chemical energy [1] which says (usefully) "the fundamental equation for the internal energy may involve terms for chemical work, gravitational work, work of electric transport, elongation work, surface work, work of electric and magnetic polarization, and other kinds of work. (p2, 1st para)
Intuitively thermal energy should be related to temperature and not internal energy, so it should it include the internal energy contained in the vibrations and rotations of complex molecules? These 'internal energy stores' only serve to increase the energy needed to raise the molecules temperature. Much the same can be said of latent heat which is (mostly) the potential energy due to intermolecular forces. Since 'latent heat' is a form of potential energy, temperature is not a function of the energy decribed by the term 'latent heat'. The 6th paragraph should infact be completely revised since when refering to liquids and solids it doesn't do anything to explain the relationship between the energy contained in particle momentum of a gas and that in the resonating harmonic structures in liquids and solids.
7/ The 7th is quite mistaken, it should say "differences in temperature are the driving force for energy transfer" (NB not 'thermal energy' because that would needlessly imply a temperature change), that is what the 2nd Law is all about, since temperature is the measure of thermal energy density i.e. Joules per degree of freedom. Of course thermal energy does not include latent heat, chemical bond energy etc. etc. -- Damorbel ( talk) 11:28, 3 November 2010 (UTC)
Does anyone else feel that this article is being over edited? While it is absolutely, positively apparent that this article needs an extensive amount of work, continuously editing the article WITHOUT thorough discussion is leading the article into a downward spiral. Why are so many edits being made without having at least some sort of consensus among active editors? Can we please do something about this? Sirsparksalot ( talk) 23:01, 3 November 2010 (UTC)
To get some simplicity, address the relationship between temperature and kinetic energy of the gas molecules and liquid molecules of water in a pressure cooker on a stove top at 212 degrees F. The temperature is the same while the kinetic energy of the gas molecules is much more. Isn't temperature the intensity of the energy and not the amount of energy? Geweber ( talk) 04:42, 25 January 2011 (UTC)
If the description of the system requires variations in the intensive parameters that are too large, the very assumptions upon which the definitions of these intensive parameters are based will break down, and the system will be in neither global nor local equilibrium. For example, it takes a certain number of collisions for a particle to equilibrate to its surroundings. If the average distance it has moved during these collisions removes it from the neighborhood it is equilibrating to, it will never equilibrate, and there will be no LTE. Temperature is, by definition, proportional to the average internal energy of an equilibrated neighborhood. Since there is no equilibrated neighborhood, the concept of temperature breaks down, and the temperature becomes undefined.
PAR, by putting your spaces all over the place you have reduced this discussion to incoherence. You appear to be convinced that concept of temperature is only applicable to a particular volume of material which you do not define, it would help if you could explain why. Other intensive properties such as density and pressure are not restricted this way, why should temperature?
Before you make more remarks on the Avogadro constant I suggest you read this: Avogadro constant history. You will see that the current value of this constant was not established until 1926, by which time the (modern) atomic theory was quite well established; it earned the finder a Nobel prize. -- Damorbel ( talk) 16:27, 28 January 2011 (UTC)
Damorbel - ok, I made a mistake by a factor of maybe 3/2. Assume a monatomic ideal gas. The average energy of 10^9 particles with zero energy and one with energy kB*10^11 will have an average energy of kB*10^11/(1+10^9)=100kB. (close enough). A volume element with 10^9 particles with a Maxwell distribution at 66.66 degrees will have average energy (3/2) 66.66 kB = 100kB: it's the same. Classical thermodynamics will only give correct results for the second case. Thermodynamic temperature, as defined by thermodynamics, always works in thermodynamic equations, therefore the temperature as you define it for the first case, will not, therefore your definition is not consistent with the definition of thermodynamic temperature. PAR ( talk) 15:45, 30 January 2011 (UTC)
You two seem to be both arguing that something does not work. So who is claiming that something works? Kmarinas86 (Expert Sectioneer of Wikipedia) 19+9+14 + karma = 19+9+14 + talk = 86 21:22, 31 January 2011 (UTC)
Could someone provide the mathematical relationship between 700nK temperature of cesium atoms and their velocity of 7mm per second in the NIST test in 1994 to reach a low temperature? My theory is that if temperature is a physical property like velocity is then temperature is related to the frequency of the vibration of the atoms/molecules. The velocity and frequency of the vibration of molecules as a gas in a confined container have a direct correlation. However, with liquid and gas of H2O in the same container the average velocity of the gas molecules is much greater than the average velocity of the molecules in the liquid yet they have the same temperature. Since the distance between molecules in the gas is much greater the frequency of the vibration of the molecules in the liquid and gas could be the same since the temperature is the same. Until you guys can explain why the temperature of the gas and liquid in the same container is equal while the energy is much different you are not explaining temperature where the lay person can understand it. This description of temperature in Wikipedia does nothing to help me. Geweber ( talk) 18:13, 5 February 2011 (UTC)
Thermodynamics is a discipline separate from statistical mechanics and/or kinetic theory. To quote "Thermodynamics" by Enrico Fermi:
But the approach in pure thermodynamics is different. Here the fundamental laws are assumed as postulates based on experimental evidence and conclusions are drawn from them without entering into the kinetic mechanism of the pheonomena. This procedure has the advantage of being independent, to a great extent, of the simplifying assumptions that are often made in sttistical mechanical considerations.
To quote "Thermodynamics and and Introduction to Thermostatistics" by Callen:
...the amalgamation of thermodynamics and statistical mechanics runs counter to the "principle of theoretical economy".... Models, endemic to statistical mechanics, should be eschewed whenever the general method of macroscopic thermodynamics are sufficient.
Unless you can give references which state that statistical mechanics and/or the kinetic theory of gases is a sub-discipline of thermodynamics, please do not revert.
As for the Boltzmann constant, to state that it has meaning only in the SDI system of units is clearly wrong. It is a physical constant, much like the speed of light. The speed of light is not a numerical constant, the real number used to represent it changes depending on your system of units. The same is true of the Boltzmann constant. Unless you can give references which state that the Boltzmann constant has no meaning outside of the metric system of units, please do not revert. PAR ( talk) 19:30, 9 November 2010 (UTC)
As for the Boltzmann constant, it is only needed in the practical use of systems of measurement as historically developed. In pure physics, it is not needed, if you want to keep it, it's dimensionless unity, if it weren't for the need to convert to historical metric systems, it might not have been proposed for use and it probably would be called something else. It's not as fundamental or limiting as the speed of light, physics works the same without it, when all natural units are used. It always is used in the product with the thermodynamic temperature, t = kT, which is the measurement of temperature in energy units. That's its only use. If someone talks about the Boltzmann constant, it is implicitly assumed to be related to our practical system of measurement, not to natural physics, because it's not necessary there. If you want to learn more about that read M. I. Kalinin, S. A. Kononogov (2005). "Boltzmann's Constant, the Energy Meaning of Temperature, and Thermodynamic Irreversibility". Measurement Techniques. 48 (7): 632–636. doi: 10.1007/s11018-005-0195-9.. But yes, of course it's needed for any other (non-natural) system of units, but that can be learned from another article. Kbrose ( talk) 20:57, 9 November 2010 (UTC)
Statistical mechanics constitutes in large part a parallel science to thermodynamics"
Given that:
Generally:
and...
In a classical ideal gas:
It would follow that, in a classical ideal gas:
Because k is constant, this would imply that in a classical ideal gas that entropy is proportional to degrees of freedom. In other words, two ideal gases having the same number of degrees of freedom will have the same entropy regardless of their temperature. Does classical thermodynamics really assume this? Does it contradict classical thermodynamics? Or did physicists just overlook this?
siNkarma86—Expert Sectioneer of Wikipedia
86 = 19+9+14 + karma = 19+9+14 +
talk
03:38, 15 March 2011 (UTC)
In an Spiegel online quiz I learned that there is (theoretically) a maximum temperature in the universe. However they could not appropriately explain that. I am wondering if the Planck temperature in the table (shortly after the big bang) would be this maximum. The argument would be that for higher temperatures the region would isolate itself from this universe (via an event horizon, i.e. forming a black hole).
Unfortunately I cannot give any reference for that. If someone knows a reference maybe he could add a corresponding note to the entry about the Planck temperature.
Thanks MelchiorG ( talk) 10:58, 7 April 2011 (UTC)
I know wikipedia science articles can't afford to try to explain everything about any topic. However is it possible that the article could at least explain why temperature is expressed as instead of as which seems to be simpler? Zebulin ( talk) 16:19, 18 May 2011 (UTC)
I don't want to argue the accuracy, but does the article really benefit from the phrase "hotness exists on a one-dimensional manifold"? I suppose it will set straight any mathematicians out there laboring under the misconception that temperature is a Möbius strip. But for most readers... really? Spiel496 ( talk) 18:22, 9 June 2011 (UTC)
I originally went to this page hoping to get some insight into the nature of the temperature of the CMB radiation. I had a vague assumption that maybe the temperature of the CMB was the temperature that matter would reach when in thermal equilibrium with the CMB. But while the article does a pretty good job describing the nature of temperature of matter in relation to the kinetic energy of the particles in an object it's very difficult for uninformed fools such as myself to relate that concept to something other than matter like the CMB. Is it possible that something could be done in the intro to help the general public better understand temperature in the way it is used for the CMB in the same way that the article describes temperatures of matter? Thanks for any insight in improving this portion of the article! Zebulin ( talk) 14:06, 10 June 2011 (UTC)
The present section on heat capacity is nonsense, and something should be done about it. I agree with the idea of editor 121.58.217.83 to remove its present content, but I would go further and remove the whole section. It is not so relevant to an article on temperature that it cannot be dealt with just by a "see also". Chjoaygame ( talk) 04:01, 28 June 2011 (UTC)
Any discussion of temperature should include something about specific heat - the heat capacity per unit mass of a material. As for "kinetic energy", the concept is clarified in the linked article. If only a link is provided, then readers will have no idea why they might want to click on it. The current text at least provides a hint. Q Science ( talk) 22:42, 29 June 2011 (UTC)
Kelvin was not a Scot as mentioned. He was born in Belfast. He studied in Scotland also in many other places, returning to Scotland to lecture and spend most of his life. — Preceding unsigned comment added by 86.144.179.215 ( talk) 17:51, 29 June 2011 (UTC)
Surely the overview Overview is mistaken when it states "temperature tells of the tendency of matter to transfer heat from hotter to cooler bodies"? This is about the difference of temperature. How can you define a property by the effect of its differential? Temperature is the measure of thermal energy density, Joules per DOF (degree of freedom) a relationship defined by kB, the Boltzmann constant
Further in the section Theoretical foundation it says "temperature may be measured directly in units of energy" which, if it were true, would enable you to tell the doctor your temperature was 10Joules, which is quite absurd, temperature in measured in Kelvins, oFahrenheit, oCelcius etc., etc.
Further in the same section it says " microscopic descriptions are interrelated by the Boltzmann constant, a proportionality factor that scales temperature to the microscopic mean kinetic energy" which is not correct, partly because it doesn't say which kinetic energy it's referring to so we are left hanging in the air. What it should say is the energy in a DOF (degree of freedom), this allows for the acurate definition of temperature for molecules such as O2, He and CO2, all of which have different numbers of DOF and thus different kinetic energies at the same temperature. -- Damorbel ( talk) 13:59, 16 July 2011 (UTC)
"The overview is an overview". But an overview of what? It says "transfer heat from hotter to cooler bodies" which is between two temperatures, it is not about temperature but about the 2nd law of thermodynamics.
"Temperature is above all a macroscopic notion". I don't agree, temperature is "energy per particle" as defined by the Boltzmann constant. When you have a collection of particles, as in a volume of gas, exchanging energy through collisions the the particles do not all have the same energy but energy distributed according to the Maxwell–Boltzmann distribution which means that the average energy per particle, i.e. the temperature, corresponds to the the energy of a single particle with the same temperature. This should be obvious since the size of the 'collection' of particles is not defined, it can be reduced to one particle without introducing any error. -- Damorbel ( talk) 09:43, 18 July 2011 (UTC)
The animation that claims to show an ideal monatomic gas does not, in fact, do so. One of the assumptions about an ideal gas is that the particles do not interact, but the particles in the animation clearly collide and bounce off one another. Adam Lein ( talk) 19:49, 6 September 2011 (UTC)
Editor Red787 made a well-intentioned but mistaken edit, from hot and cold to exothermic and endothermic. The latter two terms refer to heat production not to hotness and coldness as such. I reverted his edits. Chjoaygame ( talk) 03:27, 24 September 2011 (UTC)
I do not like the new edit by La goutte de pluie and will probably delete it when I have examined it more carefully; I am busy elsewhere right now. La goutte de pluie may feel that the layman will benefit from his edit, but I am not so sure. Chjoaygame ( talk) 04:35, 14 October 2011 (UTC)
Absolute Zero is shown as -459.68 degrees Fahrenheit, when conversion scales in the article (and references in linked Rankine scale) indicate absolute zero would be -459.67 degrees Fahrenheit. CWallwork ( talk) 21:25, 23 October 2011 (UTC)C. Wallwork 10/23/11
Editor 219.89.117.203 changed "Some of the world" to "Most of the world', but did not offer a reliable source for change. I have therefore reverted the change.
For all I know, the change by editor 219.89.117.203 may have been for the better. But Wikipedia policy is that such a change should be supported by a reliable source, for the better or not.
Dear editor 219.89.117.203, you are of course free to make the change again, but if you do, you should supply a reliable source for it. A reliable source is not just any source that agrees with you, but one that can be reasonably verified as giving reliable information on the point. If you do not provide a clearly reliable source for a change, I will oppose the change. Chjoaygame ( talk) 02:11, 4 January 2012 (UTC)
The problem here is not as to the truth or otherwise of the edit, but is as to its conformity with the Wikipedia requirement for reliable sourcing. This is the same as for the previous edit commented on just above. If you want to make an edit like this, you need to provide a reliable source for it. It is no easy thing to provide reliable sourcing, because it calls for careful assessment of source reliability. Chjoaygame ( talk) 02:50, 8 January 2012 (UTC)
"average speed of the microscopic particles that it contains"
suggests particles that can be seen with a microscope. That is, particles which are bigger than nano-paricles, but smaller than milli-metres.
Perhaps that should read: "average speed of the atomic particles that it contains" 203.206.162.148 ( talk) 01:32, 25 January 2012 (UTC)
The 2nd line of the article has "Heat spontaneously flows from bodies of a higher temperature to bodies of lower temperature". this is the rather outdated caloric theory. It should be "Energy is transferred from bodies with a higher temperature to those with a lower temperature". Heat in measured by temperature and thus is is not a substance that can 'flow'. There are many ways a body can change its temperature, none of them involve 'flowing'! It has been said that Wikipedia is not for scientists, this reads like 'keeping the ignorant in their place' to me. -- Damorbel ( talk) 12:12, 25 January 2012 (UTC)
As long as you keep in mind that the temperature is a function of the velocity squared then you can see it as an averaging out process with the faster particles giving up energy (velocity squared) to the slower particles, and the resulting average being a square root of the sum of squares value. So it's an energy redistribution process. WFPM ( talk) 16:09, 5 April 2012 (UTC)
Spiel496 you write "I have no problem with the statement that heat "flows"," I do not doubt you but then do you also accept the Caloric theory of heat? The origin of this theory was the supposition that heat was some kind of fluid that flowed from/into materials according to temperature difference. This doesn't happen with [ [3]] friction or chemical change, or does it?
There is a restricted class of heat transfer problems that may be approximated by treating heat as if it were a fluid but care must be taken not to break the 1st law of thermodynamics. What do you think? -- Damorbel ( talk) 15:06, 8 May 2012 (UTC)
Um, sorry for omitting the signature. But may I ask why "Responding to comment from you was a mistake by me"? What I wrote is quite logical and supported by a quotation from a relevant source, a source actually cited by you in the talk pages for Heat here; your citation was p14, mine p13 §1.2.4. Don't forget these talk pages are for improving the article, not for telling the world who you want to talk to! -- Damorbel ( talk) 07:52, 9 May 2012 (UTC)
Spiel496 perhaps the question should be "is 'flowing a good analogy for heat transfer'?" Perhaps you would like to make a contribution along this line. It is true that temperature difference might be considered as an analogy for pressure difference and thus a temperature difference gives rise to energy transfer. But his flow analogy breaks down so often it is realy quite useless; unless you create some new reality e.g. flowing does not require the conservation of the material that 'flows', then how do you explain that heat is not a conserved quantity, it is energy that is conserved. Thermodynamics is a difficult subject because there are many subtle and counter intuitive interactions between matter and energy, introducing arbitrary interactions like 'heat' flowing (or perhaps it is energy that is 'flowing' - is there a distiction?) just confuse the matter and lead to many miunderstandings.
Look at it this way, what is the point of an encyclopedia if it uses second rate metaphors to explain complex matters? -- Damorbel ( talk) 14:59, 9 May 2012 (UTC)
Somewhat tangent to this section, but in 1st paragraph, shouldn't a more general term be used than "thermal conductivity" like "heat transfer resistance.". Thermal conductivity only applies to the conduction mode of heat transfer and not to radiant heat transfer. 158.35.225.227 ( talk) 16:39, 26 June 2012 (UTC)
Hopefully I can interject a bit and better understand Damorbel's point. It seems as though his main point is that in the phrase "heat flow" heat is being treated as though it is a noun. This implies that an object or substance can contain heat, which is false. This is evidenced by the fact that heat is not a state function. Because heat is a path-dependent variable, we must treat it as though the word "heat" is a verb, rather than a noun. However, the big unfortunate truth is that the word heat has been used as a noun for centuries and continues to be used as such. Unless we find a better way of using it (or a better word to replace it) we have to stick with phrases such as "heat flow." For anyone who is interested, here is info for an article that discusses this problem. (American Journal of Physics, 69 (2001), 107. Sirsparksalot ( talk) 16:39, 20 July 2012 (UTC)
It should be noted that the entry "Infinite" for the wavelength of a body of 0 temperature is pretty bogus, as such a body simply emits no black body radiation. So it should either be left empty or read something like '-'... — Preceding unsigned comment added by 82.139.196.68 ( talk) 15:39, 5 February 2012 (UTC)
If an Atom of OO9F18 is at a temperature of 0 degrees Kelvin, how can it have the kinetic energy required to break the PN bond and then capture an electron and change to EE8O18? WFPM ( talk) 15:58, 5 April 2012 (UTC)
As I understand, as multiatomic gases have more degrees of freedom than monoatomic gases and thus particles have more energy on average at the same temperature, the statement that in a mixture of gases, particles have the same average kinetic energy, does not hold in case of monoatomic and diatomic gas.
Currently the article suggests that in a mixture of helium and hydrogen, particles have the same average kinetic energy:
-- Jaan Vajakas ( talk) 12:19, 6 July 2012 (UTC)
There seems to be a misundertstanding here, arising from the fact that different species atoms/molecules have different numbers of degrees of freedom. The total energy of a particle (atom or molecule) is the sum of the energy in the different degrees of freedom. For example in the formula given above by Count Iblis <1/2 m v^2> equals 3/2 k T (Iblis' formula is only correct if the 'v' is the RMS velocity as here : which incorporates the energy from three axes or degrees of freedom) the figure 3 arises because, for a particle such as a helium atom, there are 3 degrees of freedom since the He molecule is monatomic and only has energy in 3 axes, x, y and z. Diatomic molecules (H2, O2, N2 etc.) have a degree of freedom in the bond axis that makes them diatomic, so another 1/2mv2 must be added to the kinetic energy, so the molecular energy becomes . It should be noted that the bond energy in molecules will be equal to the energy in the other 3 axes according to the equipartition of energy theorem. Despite this extra energy, diatomic (polyatomic) molecules can still only exchange energy along the 3 axes, x, y and z, there is no direct means for the energy in the bond axis to be involved in the collisions between particles, this means that the temperature is only defined by the diatomic molecules translational axes. However, the energy in all four degrees of freedom does show in the specifc heat of different gases, this can be seen by comparing the specific heats of monatomic gases (A, He, Kr etc) with the diatomic gases (H2, O2, N2 etc.) and polyatomic gases (CO2, H2O etc.).
Notice that, because the kinetic energy () always has the same number of degrees of freedom as the right hand side () which means by conventional algebra that the 'degrees of freedom' term falls out of the equation, i.e. the temperature, at equilibrium, is indepedent of the amount of material. -- Damorbel ( talk) 06:17, 12 July 2012 (UTC)
Spiel, all I was trying to do was to explain to the opening post how gases with more than one atom (three degrees of freedom) have the same temperature as gases with more. I probably used too many words! But apart from that, the article has a number of problems e.g. opening statement, 2nd para. "In thermodynamics, in a system of which the entropy is considered as an independent externally controlled variable, absolute, or thermodynamic, temperature is defined as the derivative of the internal energy with respect to the entropy." How can the entropy be considered an externally controlled variable? Is there any meaning at all in this? The first para. is even worse When a heat transfer path between them is open, heat spontaneously flows from bodies of a higher temperature to bodies of lower temperature. The flow rate increases with the temperature difference, while no heat will be exchanged between bodies of the same temperature, which are then said to be in "thermal equilibrium". The first para. is allready introducing 'temperature difference' and 'heat flow' i.e. the 2nd law, before giving more than the vaguest indication of what temperature is all about. -- Damorbel ( talk) 06:21, 14 July 2012 (UTC)
As far as I can see there is not one reference given to support the assertion in the section ' Second law of thermodynamics' where it says "It is also possible to define temperature in terms of the second law of thermodynamics which deals with entropy." Further in this section it asserts, also without reference, "... for TC = 0 K the efficiency is 100% and that efficiency becomes greater than 100% below 0 K." which is thoroughly in tune with the rest of the article but is more likely to be original research or a POV, but definitely not referenced. I propose this section be deleted. -- Damorbel ( talk) 20:50, 14 July 2012 (UTC)
"delete an obviously valid statement" How so? By definition the 2nd law is about a system in disequilibrium - surely a system in thermal disequilibrium cannot have a single temperature assigned to it? -- Damorbel ( talk) 06:19, 15 July 2012 (UTC)
"Reversible changes are so slow" Really? What does 'slow' mean?
"....the Carnot cycle) by which you can define and measure absolute temperature". Please... how?
The article is about temperature which is 'energy per degree of freedom', characterised by the Boltzmann constant; this appears twice in the article here and here. The Boltzmann constant is the only way to relate temperature and energy, that is why the Kelvin will soon be replaced by the Boltzmann constant as the fundamental constant relating the two; you can read about it here. -- Damorbel ( talk) 13:47, 15 July 2012 (UTC)
You have not given an independent support for the statement "... for TC = 0 K the efficiency is 100% and that efficiency becomes greater than 100% below 0 K." I suggest that this is an example of the perpetual motion school of thermodynamics so popular in Wikipedia! For example it is to be found also in the link that you give above as:-
Yet another example in the long history of arguments presented with efficiencies >100% that breach the 2nd law. Have a nice day! -- Damorbel ( talk) 07:31, 16 July 2012 (UTC)
I have reversred here: [ [4]] where it previously said- "...variable because it is defined without concern that the body of interest is composed of many particles, such as molecules and ions of various species. It is an..."
The original text recognises that thermodynamics is the science of particle physics, without it the basis of themal science and atomic theory disappears and most of modern physics with it. If such drastic changes are to appear in Wikipedia may I suggest that there be discussion in the talk pages first?. -- Damorbel ( talk) 08:00, 13 November 2012 (UTC)
I have removed 'Quantitavely' from the text. Temperature is an intensive property, thus it is incorrect to use 'Quantitavely' which is to be used for extensive properties such as energy; this is an important distinction in thermodynamics.
PS Sorry about my duplicate thermometer contribution! -- Damorbel ( talk) 08:55, 19 January 2013 (UTC)
The opening section has this text:-
In an ideal gas, the constituent molecules do not show internal excitations. They move according to Newton's first law of motion, freely and independently of one another, except during collisions that last for negligibly short times. The temperature of an ideal gas is proportional to the mean translational kinetic energy of its molecules.
Which is deeply flawed.
1/ An ideal gas is essentially monatomic, so it cannot be a molecule which is an assembly of two or more atoms.
2/ Molecules of all sorts do show internal excitations, that is why molecular gases frequently have higher specific heats than monatomics
3/If the opening section refers to gase it should also mention liquids and solids.
So I intend to change the above paragraph:-
The kinetic definition of temperature refers to freely and independently moving particles. A microscopic degree of freedom refers to possible microscopic kinetic and microscopic potential energy. It is the microscopic kinetic energy, in particular, the microscopic kinetic energy of translation, that is the usual specific object of interest. For example, Chapman & Cowling 1939/1970 write: "The mean translatory kinetic energy per molecule, ... , is taken to be the proportional to the thermodynamic temperature ..." A gas is a material constituted of freely and independently moving particles, except when they briefly collide or undergo other adventures. A material that is not a gas includes particles that are not freely and independently moving. This means that a microscopic degree of freedom sees a division between its kinetic and its potential energy. The whole degree of freedom has kBT of energy. For some laws of interaction, especially continuous laws, between the kinetic and potential energy the kinetic energy gets just kBT/2 of mean energy, but for others it doesn't. For these others, the mean kinetic energy doesn't necessarily get kBT/2. An ideal gas belongs to the class of material with degrees of freedom with no continuous law of interaction between the kinetic and potential energy. Freely and independently moving particles belong here; they obey the Maxwell-Boltzmann distribution law. They get kBT/2 for each component of mean translational kinetic energy. That is why one can relate their mean kinetic energy to the thermodynamic temperature. For example, Tolman on page 87 writes:
"..................Hence we may now take the relation
as applying in general to any system obeying the Maxwell-Boltzmann distribution law."
The matter of aggregation of molecules is best discussed, so far as I know, by Sir James Jeans, as cited in the text of the article. Chjoaygame ( talk) 20:50, 20 January 2013 (UTC)
Damorbel has made the following entry on my talk page.
Your revision (today) of the Temperature article
You have made a revision today [ [5]] What do you mean by :-
I made an edit to extend the introduction, which refferred previously only to ... an ideal gas, the constituent molecules do not show internal... to include all gases liquids and solids.
The point being that the particles of "...liquids and solids..." are not moving freely, they are, as are many gases and vapours, constrained by interatomic forces, that is why they are liquids, solids etc.
Now you have changed it to :-
Why do you write that the particles must be "freely and independently moving ... "? Neither solids nor liquids nor gases with composite molecules have "freely and independently moving ... particles", yet they all have a measurable temperature that is just the same for all particles in eqilibrium conditions, indeed that happens to be the main theory behind the triple point cell. -- Damorbel ( talk) 20:06, 20 January 2013 (UTC)
With respect, I have undone an edit by PAR.
The edit said something important and valuable, but did not fit where it was placed.
The edited text that I undid read as follows: "For a material in which there are freely and independently moving constituent particles, except for very low temperatures where quantum effects become important, the temperature is proportional to the mean translational kinetic energy of those particles, whether they be electrons, atoms, molecules, aggregations of molecules, or pollen grains." From this sentence, I removed the words in bold.
The words "except for very low temperatures where quantum effects become important" are a kind of pleonasm for the words which are left standing. The words that are left standing are explicit that they refer to a special situation, namely that there are freely and independently moving constituent particles, and that it is just those very carefully indicated particles that are intended as showing the proportionality. The quantum effects to which the removed words refer are just the effects that remove the freedom and independence of the constituent particles. Quantum effects are about what happens when orbits of particles no longer extend in effect to infinity, but instead represent bound states of microscopic objects, which are thus no longer free and independent. So the removed words say over again what the remaining words say, adding an explanation that looks like a disclaimer. The wording that remains was originally carefully crafted to avoid a need for such an apparent disclaimer as the removed words seem to imply. The purpose was brevity and accuracy in the lead, indicating the essential physics.
It may be very valuable for the body of the article to contain an explanation of why and how the constituent particles become no longer free and independent when the body is brought to very low temperatures where quantum effects become important. As noted just above, the quantum effects are about binding, which means lack of freedom. Such an explanation would be very welcome, and could go into some detail. But it is not necessary or appropriate as a disclaimer in the presently worded lead. Chjoaygame ( talk) 05:39, 21 January 2013 (UTC)
Chjoaygame cites James Jeans in support for his position that 'fixed' molecules (not moving freely) do not exhange kinetic energy, that only freely moving perfect gas molecules do this. James Jeans, in his book "The Dynamical Theory of Gases" (ISBN-10: 0521744784) writes (p2)
Ths is as good a summary of heat and temperature as you are likely to find. -- Damorbel ( talk) 07:14, 21 January 2013 (UTC)
Damorbel has posted the following on my talk page.
James Jeans? 1904?
[7] So I got it wrong did I? So by 1940 he changed his mind did he? Chjoaygame, you are doing it again with your insinuations. If you are saying I got it wrong then why did you not cite like I did? If you merely imply, as you did, that I was incompetent, what you have written becomes an random personal attack.
If indeed James Jeans changed his mind between 1904 and 1940 (I cannot find a 1940 edition of "The Dynamical Theory of Gases". Perhaps you are thinking of "An Introduction to the Kinetic Theory of Gases" which was published for the first time in 1940; perhaps you have been looking in the wrong book ... ! Let me know when you have looked in the book I referenced, I did give a link. -- Damorbel ( talk) 10:29, 21 January 2013 (UTC)
Please do not put personal matters on these talk pages.-- Damorbel ( talk) 12:21, 21 January 2013 (UTC)
After recent discussion, does anybody consider this phrase (opening statement) :-
covers the case for the temperature of gases, solids and liquids in a satisfactory way?
And if so why?
I don't think it is correct to deccribe particles in solids and liquids as "freely moving" because they are constrained by interatomic forces. -- Damorbel ( talk) 18:54, 21 January 2013 (UTC)
Sorry but what you write, if I understand you correctly, does not include an explanation of the concept of temperature in solids and liquids. I suggest the introduction to the Heat article would be substantially improved if some text on this aspect of temperature was included. -- Damorbel ( talk) 20:58, 21 January 2013 (UTC)
Good, you do that for the stastical mechanics and will do it for the opening statement. OK? -- Damorbel ( talk) 17:32, 22 January 2013 (UTC)
I know Chjoaygame means well, but the Lead section has become unreadable. In particular, the 4th paragraph reads like a terms-of-service agreement. I could pick apart each phrase that bothers me, but I don't want this to sound like a personal attack. Please read it out loud to yourself and approach it from the point of view of someone asking the question "what is temperature, really?". Of course, we don't want to "dumb it down" -- I get that -- but we should be able to write something that at least makes sense to a layperson. I have trouble following the text, despite a degree in physics. To someone with less experience in thermodynamics, the text says effectively, "Temperature is a subtle, complex concept that you have no hope of understanding." We can do better. In fact, we could do better by simply rolling back the article to
Dec 5th.
I propose we keep the Dec 5th version in place while Chjoaygame, Damorbel and others work out the wording on this Talk page. Spiel496 ( talk) 20:25, 22 January 2013 (UTC)
Changed paragraph: Two bodies can be out of equilibrium, yet at the same temperature. If they are separated by a permeable membrane which allows particles to pass through, and are at different densities, for example. Only when they have fixed number of particles, and fixed volume will equal temperatures imply equilibrium.
Removed the paragraph:
A system achieves thermal equilibrium as internal temperature differences reduce progressively (see energy .... flows; above). Energy does not literally flow because it is not a fluid (see caloric), it is a convenient concept but a mistaken one. What is popularly called energy (or heat) flow is in fact momentum. This is fairly easy to understand from the thermal models of gases, where particles collide to exchange energy. Again energy is a useful simplification, but it is not a vector quantity so it does not have a vector's directional value that is required for the concept of 'flowing'. So it is by momentum exchange that particles arrive at equilibrium. Frequently, by way of simplification it is said that particle exchange thermal energy 'by means of translational kinetic energy' which is less elegant and less accurate than 'momentum' since the vector component is not correctly included in 'translational kinetic energy'.
Its just too jam-packed with errors to survive. "What is popularly called energy (or heat) flow is in fact momentum". Totally wrong. Heat flow is energy flow, period. "energy... is not a vector quantity so it does not have a vector's directional value that is required for the concept of flowing" - thats wrong, or else mass doesn't flow either. Mass and energy flow because they have a flux vector (mass density x velocity, energy density x velocity), which provides the vector nature. Etc. Etc. PAR ( talk) 06:40, 23 January 2013 (UTC)
"Flow' off topic? The section is about equilibrium! Without equilibrium the concept of temperature is meaningless.
Worse than that the concept of heat flowing is rejected in my contribution. I understand from your 'off topic' assertion that it is a viable concept.
Sorry but I am not convinced by your arguments. Would you care to clarify your position on both heat 'flow' or '(thermal) equilibrium'?
These are matters of physics, do you really think that they can be so narrowly separated? It's like saying legs are 'off topic' in an article on tables! -- Damorbel ( talk) 18:10, 23 January 2013 (UTC)
Spiel496, I am utterly astonished by your conviction that temperature, energy transfer and equilibrium can be separated, temperature can only exist in an equilibrium state and equilibrium states can only be reached by energy transfer (or momentum transfer, if you care).
It is quite irresponsible not to refer to the principle matters in the opening section in an encyclopedia. Leaving relevant material out is properly called 'dumbing down'. I know some people find thermal physics 'difficult' but I don't think they will be helped by leaving critical material out. -- Damorbel ( talk) 19:06, 23 January 2013 (UTC)
It may appear to be pernickety but I have restored the practical in
Temperature is a measure of particle energy, just like electron volts.
There are however 'impractical' upper limits :-
1/ How do you give the particle extreme energy?
2/ Does the particle actually survive the application of extreme energy? e.g LHC
Oh alright, the second one is really about acceleration! But I do think 'practical' is relevant. -- Damorbel ( talk) 18:52, 23 January 2013 (UTC)
The lead contains the statement that "Temperature is a property of all materials, gas, solid or liquid." It is also a property of radiation. I think the lead should allow for this. I will leave it for the current activists to fix. Chjoaygame ( talk) 01:55, 24 January 2013 (UTC)
The lead includes the clause "the amplitude of the vibrations is also zero". This is not good enough. I will leave it to the current activists to fix it. Chjoaygame ( talk) 02:06, 24 January 2013 (UTC)
I mean to say 'what vibrations'? Chjoaygame ( talk) 00:05, 25 January 2013 (UTC)
The lead now includes the following: "Temperature is an intensive property, meaning that it does not scale with the size of a system, ...". This is vague and unsatisfactory for a lead. It is not rescued by the next clause "and that it can vary from one location to another." It is not enough to define intensiveness by saying that it is not a scaling property. I will leave it to the current activists to fix. Chjoaygame ( talk) 01:52, 24 January 2013 (UTC)
I can't understand what this means: It refers to the state of matter or radiation in a locality, and can vary between locations? It's awkward-sounding. Would it be equivalent to say "Temperature can vary with location."? Spiel496 ( talk) 20:01, 25 January 2013 (UTC)
Or "It is a property of matter or radiation that can vary with location"?. Do we really need to say that temperature has spatial variation? The alternative would be a universe with uniform temperature. Everyone knows that isn't the situation. Spiel496 ( talk) 20:09, 25 January 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 1 | Archive 2 | Archive 3 | Archive 4 | Archive 5 | Archive 6 |
1/ Opening paragraph - replace 'warm' with 'warmer' & 'hot' with 'hotter' (temperature is relative (2nd Law))
2/ 2nd paragraph has nothing to do with temperature per se and everything to do with a thermometer, i.e. how to measure it. To clarify, temperature as a measure of the concentration of thermal energy, temperature exists independently of however many systems are defined by the observer!
3/ 3rd (see 2/ above) should indicate very clearly that scales of temperature are there purely for the convenience of the observer and can be defined in any convenient way.
4/ 4th paragraph has no place in an introduction. Cleaned up, it might have a place under a section called 'History' which is yet to be written!
5/ 5th para. is completely confused, e.g. the first phrase "Microscopically, temperature determines the statistical distribution and the mean value of energy of motion" - not remotely true, check Maxwell-Boltzmann statistics or Maxwell-Boltzmann distribution (why on earth are there two articles for this in Wikipedia?) Microsopicaly means 'at the smallest possible subdivision', which is a 'degree of freedom' in this instance.
6/ 6th para. Much the same as the 5th. It refers to Thermal energy which redirects to Internal energy which opens with "internal energy is the total energy contained by a thermodynamic system" together with a reference to an article on chemical energy [1] which says (usefully) "the fundamental equation for the internal energy may involve terms for chemical work, gravitational work, work of electric transport, elongation work, surface work, work of electric and magnetic polarization, and other kinds of work. (p2, 1st para)
Intuitively thermal energy should be related to temperature and not internal energy, so it should it include the internal energy contained in the vibrations and rotations of complex molecules? These 'internal energy stores' only serve to increase the energy needed to raise the molecules temperature. Much the same can be said of latent heat which is (mostly) the potential energy due to intermolecular forces. Since 'latent heat' is a form of potential energy, temperature is not a function of the energy decribed by the term 'latent heat'. The 6th paragraph should infact be completely revised since when refering to liquids and solids it doesn't do anything to explain the relationship between the energy contained in particle momentum of a gas and that in the resonating harmonic structures in liquids and solids.
7/ The 7th is quite mistaken, it should say "differences in temperature are the driving force for energy transfer" (NB not 'thermal energy' because that would needlessly imply a temperature change), that is what the 2nd Law is all about, since temperature is the measure of thermal energy density i.e. Joules per degree of freedom. Of course thermal energy does not include latent heat, chemical bond energy etc. etc. -- Damorbel ( talk) 11:28, 3 November 2010 (UTC)
Does anyone else feel that this article is being over edited? While it is absolutely, positively apparent that this article needs an extensive amount of work, continuously editing the article WITHOUT thorough discussion is leading the article into a downward spiral. Why are so many edits being made without having at least some sort of consensus among active editors? Can we please do something about this? Sirsparksalot ( talk) 23:01, 3 November 2010 (UTC)
To get some simplicity, address the relationship between temperature and kinetic energy of the gas molecules and liquid molecules of water in a pressure cooker on a stove top at 212 degrees F. The temperature is the same while the kinetic energy of the gas molecules is much more. Isn't temperature the intensity of the energy and not the amount of energy? Geweber ( talk) 04:42, 25 January 2011 (UTC)
If the description of the system requires variations in the intensive parameters that are too large, the very assumptions upon which the definitions of these intensive parameters are based will break down, and the system will be in neither global nor local equilibrium. For example, it takes a certain number of collisions for a particle to equilibrate to its surroundings. If the average distance it has moved during these collisions removes it from the neighborhood it is equilibrating to, it will never equilibrate, and there will be no LTE. Temperature is, by definition, proportional to the average internal energy of an equilibrated neighborhood. Since there is no equilibrated neighborhood, the concept of temperature breaks down, and the temperature becomes undefined.
PAR, by putting your spaces all over the place you have reduced this discussion to incoherence. You appear to be convinced that concept of temperature is only applicable to a particular volume of material which you do not define, it would help if you could explain why. Other intensive properties such as density and pressure are not restricted this way, why should temperature?
Before you make more remarks on the Avogadro constant I suggest you read this: Avogadro constant history. You will see that the current value of this constant was not established until 1926, by which time the (modern) atomic theory was quite well established; it earned the finder a Nobel prize. -- Damorbel ( talk) 16:27, 28 January 2011 (UTC)
Damorbel - ok, I made a mistake by a factor of maybe 3/2. Assume a monatomic ideal gas. The average energy of 10^9 particles with zero energy and one with energy kB*10^11 will have an average energy of kB*10^11/(1+10^9)=100kB. (close enough). A volume element with 10^9 particles with a Maxwell distribution at 66.66 degrees will have average energy (3/2) 66.66 kB = 100kB: it's the same. Classical thermodynamics will only give correct results for the second case. Thermodynamic temperature, as defined by thermodynamics, always works in thermodynamic equations, therefore the temperature as you define it for the first case, will not, therefore your definition is not consistent with the definition of thermodynamic temperature. PAR ( talk) 15:45, 30 January 2011 (UTC)
You two seem to be both arguing that something does not work. So who is claiming that something works? Kmarinas86 (Expert Sectioneer of Wikipedia) 19+9+14 + karma = 19+9+14 + talk = 86 21:22, 31 January 2011 (UTC)
Could someone provide the mathematical relationship between 700nK temperature of cesium atoms and their velocity of 7mm per second in the NIST test in 1994 to reach a low temperature? My theory is that if temperature is a physical property like velocity is then temperature is related to the frequency of the vibration of the atoms/molecules. The velocity and frequency of the vibration of molecules as a gas in a confined container have a direct correlation. However, with liquid and gas of H2O in the same container the average velocity of the gas molecules is much greater than the average velocity of the molecules in the liquid yet they have the same temperature. Since the distance between molecules in the gas is much greater the frequency of the vibration of the molecules in the liquid and gas could be the same since the temperature is the same. Until you guys can explain why the temperature of the gas and liquid in the same container is equal while the energy is much different you are not explaining temperature where the lay person can understand it. This description of temperature in Wikipedia does nothing to help me. Geweber ( talk) 18:13, 5 February 2011 (UTC)
Thermodynamics is a discipline separate from statistical mechanics and/or kinetic theory. To quote "Thermodynamics" by Enrico Fermi:
But the approach in pure thermodynamics is different. Here the fundamental laws are assumed as postulates based on experimental evidence and conclusions are drawn from them without entering into the kinetic mechanism of the pheonomena. This procedure has the advantage of being independent, to a great extent, of the simplifying assumptions that are often made in sttistical mechanical considerations.
To quote "Thermodynamics and and Introduction to Thermostatistics" by Callen:
...the amalgamation of thermodynamics and statistical mechanics runs counter to the "principle of theoretical economy".... Models, endemic to statistical mechanics, should be eschewed whenever the general method of macroscopic thermodynamics are sufficient.
Unless you can give references which state that statistical mechanics and/or the kinetic theory of gases is a sub-discipline of thermodynamics, please do not revert.
As for the Boltzmann constant, to state that it has meaning only in the SDI system of units is clearly wrong. It is a physical constant, much like the speed of light. The speed of light is not a numerical constant, the real number used to represent it changes depending on your system of units. The same is true of the Boltzmann constant. Unless you can give references which state that the Boltzmann constant has no meaning outside of the metric system of units, please do not revert. PAR ( talk) 19:30, 9 November 2010 (UTC)
As for the Boltzmann constant, it is only needed in the practical use of systems of measurement as historically developed. In pure physics, it is not needed, if you want to keep it, it's dimensionless unity, if it weren't for the need to convert to historical metric systems, it might not have been proposed for use and it probably would be called something else. It's not as fundamental or limiting as the speed of light, physics works the same without it, when all natural units are used. It always is used in the product with the thermodynamic temperature, t = kT, which is the measurement of temperature in energy units. That's its only use. If someone talks about the Boltzmann constant, it is implicitly assumed to be related to our practical system of measurement, not to natural physics, because it's not necessary there. If you want to learn more about that read M. I. Kalinin, S. A. Kononogov (2005). "Boltzmann's Constant, the Energy Meaning of Temperature, and Thermodynamic Irreversibility". Measurement Techniques. 48 (7): 632–636. doi: 10.1007/s11018-005-0195-9.. But yes, of course it's needed for any other (non-natural) system of units, but that can be learned from another article. Kbrose ( talk) 20:57, 9 November 2010 (UTC)
Statistical mechanics constitutes in large part a parallel science to thermodynamics"
Given that:
Generally:
and...
In a classical ideal gas:
It would follow that, in a classical ideal gas:
Because k is constant, this would imply that in a classical ideal gas that entropy is proportional to degrees of freedom. In other words, two ideal gases having the same number of degrees of freedom will have the same entropy regardless of their temperature. Does classical thermodynamics really assume this? Does it contradict classical thermodynamics? Or did physicists just overlook this?
siNkarma86—Expert Sectioneer of Wikipedia
86 = 19+9+14 + karma = 19+9+14 +
talk
03:38, 15 March 2011 (UTC)
In an Spiegel online quiz I learned that there is (theoretically) a maximum temperature in the universe. However they could not appropriately explain that. I am wondering if the Planck temperature in the table (shortly after the big bang) would be this maximum. The argument would be that for higher temperatures the region would isolate itself from this universe (via an event horizon, i.e. forming a black hole).
Unfortunately I cannot give any reference for that. If someone knows a reference maybe he could add a corresponding note to the entry about the Planck temperature.
Thanks MelchiorG ( talk) 10:58, 7 April 2011 (UTC)
I know wikipedia science articles can't afford to try to explain everything about any topic. However is it possible that the article could at least explain why temperature is expressed as instead of as which seems to be simpler? Zebulin ( talk) 16:19, 18 May 2011 (UTC)
I don't want to argue the accuracy, but does the article really benefit from the phrase "hotness exists on a one-dimensional manifold"? I suppose it will set straight any mathematicians out there laboring under the misconception that temperature is a Möbius strip. But for most readers... really? Spiel496 ( talk) 18:22, 9 June 2011 (UTC)
I originally went to this page hoping to get some insight into the nature of the temperature of the CMB radiation. I had a vague assumption that maybe the temperature of the CMB was the temperature that matter would reach when in thermal equilibrium with the CMB. But while the article does a pretty good job describing the nature of temperature of matter in relation to the kinetic energy of the particles in an object it's very difficult for uninformed fools such as myself to relate that concept to something other than matter like the CMB. Is it possible that something could be done in the intro to help the general public better understand temperature in the way it is used for the CMB in the same way that the article describes temperatures of matter? Thanks for any insight in improving this portion of the article! Zebulin ( talk) 14:06, 10 June 2011 (UTC)
The present section on heat capacity is nonsense, and something should be done about it. I agree with the idea of editor 121.58.217.83 to remove its present content, but I would go further and remove the whole section. It is not so relevant to an article on temperature that it cannot be dealt with just by a "see also". Chjoaygame ( talk) 04:01, 28 June 2011 (UTC)
Any discussion of temperature should include something about specific heat - the heat capacity per unit mass of a material. As for "kinetic energy", the concept is clarified in the linked article. If only a link is provided, then readers will have no idea why they might want to click on it. The current text at least provides a hint. Q Science ( talk) 22:42, 29 June 2011 (UTC)
Kelvin was not a Scot as mentioned. He was born in Belfast. He studied in Scotland also in many other places, returning to Scotland to lecture and spend most of his life. — Preceding unsigned comment added by 86.144.179.215 ( talk) 17:51, 29 June 2011 (UTC)
Surely the overview Overview is mistaken when it states "temperature tells of the tendency of matter to transfer heat from hotter to cooler bodies"? This is about the difference of temperature. How can you define a property by the effect of its differential? Temperature is the measure of thermal energy density, Joules per DOF (degree of freedom) a relationship defined by kB, the Boltzmann constant
Further in the section Theoretical foundation it says "temperature may be measured directly in units of energy" which, if it were true, would enable you to tell the doctor your temperature was 10Joules, which is quite absurd, temperature in measured in Kelvins, oFahrenheit, oCelcius etc., etc.
Further in the same section it says " microscopic descriptions are interrelated by the Boltzmann constant, a proportionality factor that scales temperature to the microscopic mean kinetic energy" which is not correct, partly because it doesn't say which kinetic energy it's referring to so we are left hanging in the air. What it should say is the energy in a DOF (degree of freedom), this allows for the acurate definition of temperature for molecules such as O2, He and CO2, all of which have different numbers of DOF and thus different kinetic energies at the same temperature. -- Damorbel ( talk) 13:59, 16 July 2011 (UTC)
"The overview is an overview". But an overview of what? It says "transfer heat from hotter to cooler bodies" which is between two temperatures, it is not about temperature but about the 2nd law of thermodynamics.
"Temperature is above all a macroscopic notion". I don't agree, temperature is "energy per particle" as defined by the Boltzmann constant. When you have a collection of particles, as in a volume of gas, exchanging energy through collisions the the particles do not all have the same energy but energy distributed according to the Maxwell–Boltzmann distribution which means that the average energy per particle, i.e. the temperature, corresponds to the the energy of a single particle with the same temperature. This should be obvious since the size of the 'collection' of particles is not defined, it can be reduced to one particle without introducing any error. -- Damorbel ( talk) 09:43, 18 July 2011 (UTC)
The animation that claims to show an ideal monatomic gas does not, in fact, do so. One of the assumptions about an ideal gas is that the particles do not interact, but the particles in the animation clearly collide and bounce off one another. Adam Lein ( talk) 19:49, 6 September 2011 (UTC)
Editor Red787 made a well-intentioned but mistaken edit, from hot and cold to exothermic and endothermic. The latter two terms refer to heat production not to hotness and coldness as such. I reverted his edits. Chjoaygame ( talk) 03:27, 24 September 2011 (UTC)
I do not like the new edit by La goutte de pluie and will probably delete it when I have examined it more carefully; I am busy elsewhere right now. La goutte de pluie may feel that the layman will benefit from his edit, but I am not so sure. Chjoaygame ( talk) 04:35, 14 October 2011 (UTC)
Absolute Zero is shown as -459.68 degrees Fahrenheit, when conversion scales in the article (and references in linked Rankine scale) indicate absolute zero would be -459.67 degrees Fahrenheit. CWallwork ( talk) 21:25, 23 October 2011 (UTC)C. Wallwork 10/23/11
Editor 219.89.117.203 changed "Some of the world" to "Most of the world', but did not offer a reliable source for change. I have therefore reverted the change.
For all I know, the change by editor 219.89.117.203 may have been for the better. But Wikipedia policy is that such a change should be supported by a reliable source, for the better or not.
Dear editor 219.89.117.203, you are of course free to make the change again, but if you do, you should supply a reliable source for it. A reliable source is not just any source that agrees with you, but one that can be reasonably verified as giving reliable information on the point. If you do not provide a clearly reliable source for a change, I will oppose the change. Chjoaygame ( talk) 02:11, 4 January 2012 (UTC)
The problem here is not as to the truth or otherwise of the edit, but is as to its conformity with the Wikipedia requirement for reliable sourcing. This is the same as for the previous edit commented on just above. If you want to make an edit like this, you need to provide a reliable source for it. It is no easy thing to provide reliable sourcing, because it calls for careful assessment of source reliability. Chjoaygame ( talk) 02:50, 8 January 2012 (UTC)
"average speed of the microscopic particles that it contains"
suggests particles that can be seen with a microscope. That is, particles which are bigger than nano-paricles, but smaller than milli-metres.
Perhaps that should read: "average speed of the atomic particles that it contains" 203.206.162.148 ( talk) 01:32, 25 January 2012 (UTC)
The 2nd line of the article has "Heat spontaneously flows from bodies of a higher temperature to bodies of lower temperature". this is the rather outdated caloric theory. It should be "Energy is transferred from bodies with a higher temperature to those with a lower temperature". Heat in measured by temperature and thus is is not a substance that can 'flow'. There are many ways a body can change its temperature, none of them involve 'flowing'! It has been said that Wikipedia is not for scientists, this reads like 'keeping the ignorant in their place' to me. -- Damorbel ( talk) 12:12, 25 January 2012 (UTC)
As long as you keep in mind that the temperature is a function of the velocity squared then you can see it as an averaging out process with the faster particles giving up energy (velocity squared) to the slower particles, and the resulting average being a square root of the sum of squares value. So it's an energy redistribution process. WFPM ( talk) 16:09, 5 April 2012 (UTC)
Spiel496 you write "I have no problem with the statement that heat "flows"," I do not doubt you but then do you also accept the Caloric theory of heat? The origin of this theory was the supposition that heat was some kind of fluid that flowed from/into materials according to temperature difference. This doesn't happen with [ [3]] friction or chemical change, or does it?
There is a restricted class of heat transfer problems that may be approximated by treating heat as if it were a fluid but care must be taken not to break the 1st law of thermodynamics. What do you think? -- Damorbel ( talk) 15:06, 8 May 2012 (UTC)
Um, sorry for omitting the signature. But may I ask why "Responding to comment from you was a mistake by me"? What I wrote is quite logical and supported by a quotation from a relevant source, a source actually cited by you in the talk pages for Heat here; your citation was p14, mine p13 §1.2.4. Don't forget these talk pages are for improving the article, not for telling the world who you want to talk to! -- Damorbel ( talk) 07:52, 9 May 2012 (UTC)
Spiel496 perhaps the question should be "is 'flowing a good analogy for heat transfer'?" Perhaps you would like to make a contribution along this line. It is true that temperature difference might be considered as an analogy for pressure difference and thus a temperature difference gives rise to energy transfer. But his flow analogy breaks down so often it is realy quite useless; unless you create some new reality e.g. flowing does not require the conservation of the material that 'flows', then how do you explain that heat is not a conserved quantity, it is energy that is conserved. Thermodynamics is a difficult subject because there are many subtle and counter intuitive interactions between matter and energy, introducing arbitrary interactions like 'heat' flowing (or perhaps it is energy that is 'flowing' - is there a distiction?) just confuse the matter and lead to many miunderstandings.
Look at it this way, what is the point of an encyclopedia if it uses second rate metaphors to explain complex matters? -- Damorbel ( talk) 14:59, 9 May 2012 (UTC)
Somewhat tangent to this section, but in 1st paragraph, shouldn't a more general term be used than "thermal conductivity" like "heat transfer resistance.". Thermal conductivity only applies to the conduction mode of heat transfer and not to radiant heat transfer. 158.35.225.227 ( talk) 16:39, 26 June 2012 (UTC)
Hopefully I can interject a bit and better understand Damorbel's point. It seems as though his main point is that in the phrase "heat flow" heat is being treated as though it is a noun. This implies that an object or substance can contain heat, which is false. This is evidenced by the fact that heat is not a state function. Because heat is a path-dependent variable, we must treat it as though the word "heat" is a verb, rather than a noun. However, the big unfortunate truth is that the word heat has been used as a noun for centuries and continues to be used as such. Unless we find a better way of using it (or a better word to replace it) we have to stick with phrases such as "heat flow." For anyone who is interested, here is info for an article that discusses this problem. (American Journal of Physics, 69 (2001), 107. Sirsparksalot ( talk) 16:39, 20 July 2012 (UTC)
It should be noted that the entry "Infinite" for the wavelength of a body of 0 temperature is pretty bogus, as such a body simply emits no black body radiation. So it should either be left empty or read something like '-'... — Preceding unsigned comment added by 82.139.196.68 ( talk) 15:39, 5 February 2012 (UTC)
If an Atom of OO9F18 is at a temperature of 0 degrees Kelvin, how can it have the kinetic energy required to break the PN bond and then capture an electron and change to EE8O18? WFPM ( talk) 15:58, 5 April 2012 (UTC)
As I understand, as multiatomic gases have more degrees of freedom than monoatomic gases and thus particles have more energy on average at the same temperature, the statement that in a mixture of gases, particles have the same average kinetic energy, does not hold in case of monoatomic and diatomic gas.
Currently the article suggests that in a mixture of helium and hydrogen, particles have the same average kinetic energy:
-- Jaan Vajakas ( talk) 12:19, 6 July 2012 (UTC)
There seems to be a misundertstanding here, arising from the fact that different species atoms/molecules have different numbers of degrees of freedom. The total energy of a particle (atom or molecule) is the sum of the energy in the different degrees of freedom. For example in the formula given above by Count Iblis <1/2 m v^2> equals 3/2 k T (Iblis' formula is only correct if the 'v' is the RMS velocity as here : which incorporates the energy from three axes or degrees of freedom) the figure 3 arises because, for a particle such as a helium atom, there are 3 degrees of freedom since the He molecule is monatomic and only has energy in 3 axes, x, y and z. Diatomic molecules (H2, O2, N2 etc.) have a degree of freedom in the bond axis that makes them diatomic, so another 1/2mv2 must be added to the kinetic energy, so the molecular energy becomes . It should be noted that the bond energy in molecules will be equal to the energy in the other 3 axes according to the equipartition of energy theorem. Despite this extra energy, diatomic (polyatomic) molecules can still only exchange energy along the 3 axes, x, y and z, there is no direct means for the energy in the bond axis to be involved in the collisions between particles, this means that the temperature is only defined by the diatomic molecules translational axes. However, the energy in all four degrees of freedom does show in the specifc heat of different gases, this can be seen by comparing the specific heats of monatomic gases (A, He, Kr etc) with the diatomic gases (H2, O2, N2 etc.) and polyatomic gases (CO2, H2O etc.).
Notice that, because the kinetic energy () always has the same number of degrees of freedom as the right hand side () which means by conventional algebra that the 'degrees of freedom' term falls out of the equation, i.e. the temperature, at equilibrium, is indepedent of the amount of material. -- Damorbel ( talk) 06:17, 12 July 2012 (UTC)
Spiel, all I was trying to do was to explain to the opening post how gases with more than one atom (three degrees of freedom) have the same temperature as gases with more. I probably used too many words! But apart from that, the article has a number of problems e.g. opening statement, 2nd para. "In thermodynamics, in a system of which the entropy is considered as an independent externally controlled variable, absolute, or thermodynamic, temperature is defined as the derivative of the internal energy with respect to the entropy." How can the entropy be considered an externally controlled variable? Is there any meaning at all in this? The first para. is even worse When a heat transfer path between them is open, heat spontaneously flows from bodies of a higher temperature to bodies of lower temperature. The flow rate increases with the temperature difference, while no heat will be exchanged between bodies of the same temperature, which are then said to be in "thermal equilibrium". The first para. is allready introducing 'temperature difference' and 'heat flow' i.e. the 2nd law, before giving more than the vaguest indication of what temperature is all about. -- Damorbel ( talk) 06:21, 14 July 2012 (UTC)
As far as I can see there is not one reference given to support the assertion in the section ' Second law of thermodynamics' where it says "It is also possible to define temperature in terms of the second law of thermodynamics which deals with entropy." Further in this section it asserts, also without reference, "... for TC = 0 K the efficiency is 100% and that efficiency becomes greater than 100% below 0 K." which is thoroughly in tune with the rest of the article but is more likely to be original research or a POV, but definitely not referenced. I propose this section be deleted. -- Damorbel ( talk) 20:50, 14 July 2012 (UTC)
"delete an obviously valid statement" How so? By definition the 2nd law is about a system in disequilibrium - surely a system in thermal disequilibrium cannot have a single temperature assigned to it? -- Damorbel ( talk) 06:19, 15 July 2012 (UTC)
"Reversible changes are so slow" Really? What does 'slow' mean?
"....the Carnot cycle) by which you can define and measure absolute temperature". Please... how?
The article is about temperature which is 'energy per degree of freedom', characterised by the Boltzmann constant; this appears twice in the article here and here. The Boltzmann constant is the only way to relate temperature and energy, that is why the Kelvin will soon be replaced by the Boltzmann constant as the fundamental constant relating the two; you can read about it here. -- Damorbel ( talk) 13:47, 15 July 2012 (UTC)
You have not given an independent support for the statement "... for TC = 0 K the efficiency is 100% and that efficiency becomes greater than 100% below 0 K." I suggest that this is an example of the perpetual motion school of thermodynamics so popular in Wikipedia! For example it is to be found also in the link that you give above as:-
Yet another example in the long history of arguments presented with efficiencies >100% that breach the 2nd law. Have a nice day! -- Damorbel ( talk) 07:31, 16 July 2012 (UTC)
I have reversred here: [ [4]] where it previously said- "...variable because it is defined without concern that the body of interest is composed of many particles, such as molecules and ions of various species. It is an..."
The original text recognises that thermodynamics is the science of particle physics, without it the basis of themal science and atomic theory disappears and most of modern physics with it. If such drastic changes are to appear in Wikipedia may I suggest that there be discussion in the talk pages first?. -- Damorbel ( talk) 08:00, 13 November 2012 (UTC)
I have removed 'Quantitavely' from the text. Temperature is an intensive property, thus it is incorrect to use 'Quantitavely' which is to be used for extensive properties such as energy; this is an important distinction in thermodynamics.
PS Sorry about my duplicate thermometer contribution! -- Damorbel ( talk) 08:55, 19 January 2013 (UTC)
The opening section has this text:-
In an ideal gas, the constituent molecules do not show internal excitations. They move according to Newton's first law of motion, freely and independently of one another, except during collisions that last for negligibly short times. The temperature of an ideal gas is proportional to the mean translational kinetic energy of its molecules.
Which is deeply flawed.
1/ An ideal gas is essentially monatomic, so it cannot be a molecule which is an assembly of two or more atoms.
2/ Molecules of all sorts do show internal excitations, that is why molecular gases frequently have higher specific heats than monatomics
3/If the opening section refers to gase it should also mention liquids and solids.
So I intend to change the above paragraph:-
The kinetic definition of temperature refers to freely and independently moving particles. A microscopic degree of freedom refers to possible microscopic kinetic and microscopic potential energy. It is the microscopic kinetic energy, in particular, the microscopic kinetic energy of translation, that is the usual specific object of interest. For example, Chapman & Cowling 1939/1970 write: "The mean translatory kinetic energy per molecule, ... , is taken to be the proportional to the thermodynamic temperature ..." A gas is a material constituted of freely and independently moving particles, except when they briefly collide or undergo other adventures. A material that is not a gas includes particles that are not freely and independently moving. This means that a microscopic degree of freedom sees a division between its kinetic and its potential energy. The whole degree of freedom has kBT of energy. For some laws of interaction, especially continuous laws, between the kinetic and potential energy the kinetic energy gets just kBT/2 of mean energy, but for others it doesn't. For these others, the mean kinetic energy doesn't necessarily get kBT/2. An ideal gas belongs to the class of material with degrees of freedom with no continuous law of interaction between the kinetic and potential energy. Freely and independently moving particles belong here; they obey the Maxwell-Boltzmann distribution law. They get kBT/2 for each component of mean translational kinetic energy. That is why one can relate their mean kinetic energy to the thermodynamic temperature. For example, Tolman on page 87 writes:
"..................Hence we may now take the relation
as applying in general to any system obeying the Maxwell-Boltzmann distribution law."
The matter of aggregation of molecules is best discussed, so far as I know, by Sir James Jeans, as cited in the text of the article. Chjoaygame ( talk) 20:50, 20 January 2013 (UTC)
Damorbel has made the following entry on my talk page.
Your revision (today) of the Temperature article
You have made a revision today [ [5]] What do you mean by :-
I made an edit to extend the introduction, which refferred previously only to ... an ideal gas, the constituent molecules do not show internal... to include all gases liquids and solids.
The point being that the particles of "...liquids and solids..." are not moving freely, they are, as are many gases and vapours, constrained by interatomic forces, that is why they are liquids, solids etc.
Now you have changed it to :-
Why do you write that the particles must be "freely and independently moving ... "? Neither solids nor liquids nor gases with composite molecules have "freely and independently moving ... particles", yet they all have a measurable temperature that is just the same for all particles in eqilibrium conditions, indeed that happens to be the main theory behind the triple point cell. -- Damorbel ( talk) 20:06, 20 January 2013 (UTC)
With respect, I have undone an edit by PAR.
The edit said something important and valuable, but did not fit where it was placed.
The edited text that I undid read as follows: "For a material in which there are freely and independently moving constituent particles, except for very low temperatures where quantum effects become important, the temperature is proportional to the mean translational kinetic energy of those particles, whether they be electrons, atoms, molecules, aggregations of molecules, or pollen grains." From this sentence, I removed the words in bold.
The words "except for very low temperatures where quantum effects become important" are a kind of pleonasm for the words which are left standing. The words that are left standing are explicit that they refer to a special situation, namely that there are freely and independently moving constituent particles, and that it is just those very carefully indicated particles that are intended as showing the proportionality. The quantum effects to which the removed words refer are just the effects that remove the freedom and independence of the constituent particles. Quantum effects are about what happens when orbits of particles no longer extend in effect to infinity, but instead represent bound states of microscopic objects, which are thus no longer free and independent. So the removed words say over again what the remaining words say, adding an explanation that looks like a disclaimer. The wording that remains was originally carefully crafted to avoid a need for such an apparent disclaimer as the removed words seem to imply. The purpose was brevity and accuracy in the lead, indicating the essential physics.
It may be very valuable for the body of the article to contain an explanation of why and how the constituent particles become no longer free and independent when the body is brought to very low temperatures where quantum effects become important. As noted just above, the quantum effects are about binding, which means lack of freedom. Such an explanation would be very welcome, and could go into some detail. But it is not necessary or appropriate as a disclaimer in the presently worded lead. Chjoaygame ( talk) 05:39, 21 January 2013 (UTC)
Chjoaygame cites James Jeans in support for his position that 'fixed' molecules (not moving freely) do not exhange kinetic energy, that only freely moving perfect gas molecules do this. James Jeans, in his book "The Dynamical Theory of Gases" (ISBN-10: 0521744784) writes (p2)
Ths is as good a summary of heat and temperature as you are likely to find. -- Damorbel ( talk) 07:14, 21 January 2013 (UTC)
Damorbel has posted the following on my talk page.
James Jeans? 1904?
[7] So I got it wrong did I? So by 1940 he changed his mind did he? Chjoaygame, you are doing it again with your insinuations. If you are saying I got it wrong then why did you not cite like I did? If you merely imply, as you did, that I was incompetent, what you have written becomes an random personal attack.
If indeed James Jeans changed his mind between 1904 and 1940 (I cannot find a 1940 edition of "The Dynamical Theory of Gases". Perhaps you are thinking of "An Introduction to the Kinetic Theory of Gases" which was published for the first time in 1940; perhaps you have been looking in the wrong book ... ! Let me know when you have looked in the book I referenced, I did give a link. -- Damorbel ( talk) 10:29, 21 January 2013 (UTC)
Please do not put personal matters on these talk pages.-- Damorbel ( talk) 12:21, 21 January 2013 (UTC)
After recent discussion, does anybody consider this phrase (opening statement) :-
covers the case for the temperature of gases, solids and liquids in a satisfactory way?
And if so why?
I don't think it is correct to deccribe particles in solids and liquids as "freely moving" because they are constrained by interatomic forces. -- Damorbel ( talk) 18:54, 21 January 2013 (UTC)
Sorry but what you write, if I understand you correctly, does not include an explanation of the concept of temperature in solids and liquids. I suggest the introduction to the Heat article would be substantially improved if some text on this aspect of temperature was included. -- Damorbel ( talk) 20:58, 21 January 2013 (UTC)
Good, you do that for the stastical mechanics and will do it for the opening statement. OK? -- Damorbel ( talk) 17:32, 22 January 2013 (UTC)
I know Chjoaygame means well, but the Lead section has become unreadable. In particular, the 4th paragraph reads like a terms-of-service agreement. I could pick apart each phrase that bothers me, but I don't want this to sound like a personal attack. Please read it out loud to yourself and approach it from the point of view of someone asking the question "what is temperature, really?". Of course, we don't want to "dumb it down" -- I get that -- but we should be able to write something that at least makes sense to a layperson. I have trouble following the text, despite a degree in physics. To someone with less experience in thermodynamics, the text says effectively, "Temperature is a subtle, complex concept that you have no hope of understanding." We can do better. In fact, we could do better by simply rolling back the article to
Dec 5th.
I propose we keep the Dec 5th version in place while Chjoaygame, Damorbel and others work out the wording on this Talk page. Spiel496 ( talk) 20:25, 22 January 2013 (UTC)
Changed paragraph: Two bodies can be out of equilibrium, yet at the same temperature. If they are separated by a permeable membrane which allows particles to pass through, and are at different densities, for example. Only when they have fixed number of particles, and fixed volume will equal temperatures imply equilibrium.
Removed the paragraph:
A system achieves thermal equilibrium as internal temperature differences reduce progressively (see energy .... flows; above). Energy does not literally flow because it is not a fluid (see caloric), it is a convenient concept but a mistaken one. What is popularly called energy (or heat) flow is in fact momentum. This is fairly easy to understand from the thermal models of gases, where particles collide to exchange energy. Again energy is a useful simplification, but it is not a vector quantity so it does not have a vector's directional value that is required for the concept of 'flowing'. So it is by momentum exchange that particles arrive at equilibrium. Frequently, by way of simplification it is said that particle exchange thermal energy 'by means of translational kinetic energy' which is less elegant and less accurate than 'momentum' since the vector component is not correctly included in 'translational kinetic energy'.
Its just too jam-packed with errors to survive. "What is popularly called energy (or heat) flow is in fact momentum". Totally wrong. Heat flow is energy flow, period. "energy... is not a vector quantity so it does not have a vector's directional value that is required for the concept of flowing" - thats wrong, or else mass doesn't flow either. Mass and energy flow because they have a flux vector (mass density x velocity, energy density x velocity), which provides the vector nature. Etc. Etc. PAR ( talk) 06:40, 23 January 2013 (UTC)
"Flow' off topic? The section is about equilibrium! Without equilibrium the concept of temperature is meaningless.
Worse than that the concept of heat flowing is rejected in my contribution. I understand from your 'off topic' assertion that it is a viable concept.
Sorry but I am not convinced by your arguments. Would you care to clarify your position on both heat 'flow' or '(thermal) equilibrium'?
These are matters of physics, do you really think that they can be so narrowly separated? It's like saying legs are 'off topic' in an article on tables! -- Damorbel ( talk) 18:10, 23 January 2013 (UTC)
Spiel496, I am utterly astonished by your conviction that temperature, energy transfer and equilibrium can be separated, temperature can only exist in an equilibrium state and equilibrium states can only be reached by energy transfer (or momentum transfer, if you care).
It is quite irresponsible not to refer to the principle matters in the opening section in an encyclopedia. Leaving relevant material out is properly called 'dumbing down'. I know some people find thermal physics 'difficult' but I don't think they will be helped by leaving critical material out. -- Damorbel ( talk) 19:06, 23 January 2013 (UTC)
It may appear to be pernickety but I have restored the practical in
Temperature is a measure of particle energy, just like electron volts.
There are however 'impractical' upper limits :-
1/ How do you give the particle extreme energy?
2/ Does the particle actually survive the application of extreme energy? e.g LHC
Oh alright, the second one is really about acceleration! But I do think 'practical' is relevant. -- Damorbel ( talk) 18:52, 23 January 2013 (UTC)
The lead contains the statement that "Temperature is a property of all materials, gas, solid or liquid." It is also a property of radiation. I think the lead should allow for this. I will leave it for the current activists to fix. Chjoaygame ( talk) 01:55, 24 January 2013 (UTC)
The lead includes the clause "the amplitude of the vibrations is also zero". This is not good enough. I will leave it to the current activists to fix it. Chjoaygame ( talk) 02:06, 24 January 2013 (UTC)
I mean to say 'what vibrations'? Chjoaygame ( talk) 00:05, 25 January 2013 (UTC)
The lead now includes the following: "Temperature is an intensive property, meaning that it does not scale with the size of a system, ...". This is vague and unsatisfactory for a lead. It is not rescued by the next clause "and that it can vary from one location to another." It is not enough to define intensiveness by saying that it is not a scaling property. I will leave it to the current activists to fix. Chjoaygame ( talk) 01:52, 24 January 2013 (UTC)
I can't understand what this means: It refers to the state of matter or radiation in a locality, and can vary between locations? It's awkward-sounding. Would it be equivalent to say "Temperature can vary with location."? Spiel496 ( talk) 20:01, 25 January 2013 (UTC)
Or "It is a property of matter or radiation that can vary with location"?. Do we really need to say that temperature has spatial variation? The alternative would be a universe with uniform temperature. Everyone knows that isn't the situation. Spiel496 ( talk) 20:09, 25 January 2013 (UTC)