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There is a nice animation with this caption...
'Heat energy stored in these motions does not contribute to the temperature of a substance.'
This is misleading and misguided. An improvement would be: 'as the temperature of a substance increases, the magnitude of motions like these increases'. Or ' When a body gets hotter, the heat energy supplied is going into motions like these. ' Or ' When a body's temperature is increased, the heat energy supplied is going into motions like these. '
Djcmackay 11:02, 25 January 2007 (UTC) David MacKay
I don't see the reason for having a separate page called Heat_Capacity. The material here should be merged over.
Djcmackay 21:38, 25 January 2007 (UTC)
The history prior to 7 July 2006 has been deleted because this article has been completely revised since then. Greg L 17:41, 21 July 2006 (UTC)
I'm a big fan of reporting units consistently. All disciplines tend to use specific conventions -- throw in holdovers from days gone by and it's easy to get confused. Should we change the tabulated specific heat capacity values to S.I. units, i.e. add the "x 10^3?" Todd Johnston 16:21, 8 June 2006 (UTC)
Hello,
I noticed two problems with specific heat capacity of the substances. Specific heat capacity varies based on temperature and phase. I reccomend setting the temperature to 298.15 kelvin because it seems the most popular in text books and manuals.
Please recalculate these values because what is currently shown is simply wrong!
I think the heat capacity for gold is incorrect currently 0.2291 which is not 25.42J/K/mole / 197 g/mole the correct value I believe should be around 0.129 see http://www.efunda.com/materials/elements/HC_Table.cfm?Element_ID=Au I have edited it to be in line with this RichardMathie ( talk) 18:12, 26 July 2009 (UTC)
Hi,
I once posed a question here, that I now find missing. From the history is see that Greg L blanked all the previous discussions? Why? Shouldn't they at least be archived?
The modern SI units for measuring specific heat capacity are either the Joule per gram per kelvin (J g–1 K–1) or the Joule per mole per kelvin (J mol–1 K–1). The various SI prefixes can create variations of these units (such as kJ kg–1 K–1 and kJ mol–1 K–1). Other units of measure are often employed in the measure of specific heat capacity. These include calories and BTUs for energy, pounds-mass for quantity, and degree Fahrenheit (°F) for the increment of temperature.
Can anybody tell me about the SI units above? I am doubtful because as far as I know, the SI unit for the mass is kilogram (kg).
Thanks for everybody help. Yves Revi 22:43, 28 October 2006 (UTC)
-> more degrees of freedom or Dulong-Petit not the upper boundary or else ?
The molar mass of water is (2*1,008+15,999)g/mol = 18,015 g/mol. In 1g water are therefore 2*0,055509 mol H-atoms(!) und 0,055509 mol O-atoms.
The maximum value -according Dulong-Petit law- of the specific heat capacity of liquid water is therefore 2*0,055509g/mol*3R +0,055509g/mol*3R = 0,499958g/mol * 8,3145 J/molK =4,154 J/gK. But the real value is 4,18-4,19 J/gK. It's 0,7% bigger!(not much but well above the error boundaries)
What is the explanation of this? (31 October 2006)
—The preceding unsigned comment was added by 84.152.105.34 ( talk) 14:36, 24 December 2006 (UTC).
Should:
six degrees of freedom comprising translational motion
read
three degrees of freedom comprising translational motion?
Pmilne 13:02, 4 November 2006 (UTC)
Also -
There is more than six DOF for water. I'll change it if no-one argues.-- 136.2.1.101 18:25, 10 November 2006 (UTC)
---
Specific heat capacity of steel?
my book says that the specific heat of water is 4190, why is it differnt on wiki
Check the units in your book against the units on the table. The specific heat for water is around 4.19 Joules per gram per Celsius degree, but if you list it in Joules per kilogram per Celsius degree the value would be 1000 times greater - that is, 4190. (You'd also get 4190 if you listed the heat in kiloJoules per cubic meter per Celsius degree, although that equivalence only works for materials with a specific density of 1.) Jasonfahy 21:54, 5 December 2006 (UTC)
Yea, i checked um, AND asked my teacher the book had it as J/kg*C so now i feel kinda stupid Chuck61007
I have corrected want to point out a serious misinterpretation of the heat capacity of water vapor. Water molecules do not have "a maxiumu of six degrees of freedom", they have nine, 3 each for translation, rotation, and vibration.The vibrational d.f. are mostly "frozen out" at T=100C, so the zero-order estimate for Cv is (3/2 R) for translation + (3/2 R) for rotation = 3R. For an ideal gas Cp =Cv + R, so you expect
Cp approximately equal to 4R, ie. 33.26 J/mol K. This is slighly less than the value in the table, 37.47,
just what one expects since the bending vibration is fairly low frequency and is therefore not
completely frozen out. The fact that the final answer is close to twice that of a monatomic gas
is a numerical coincidence - if the vibrational contribution were completely frozen, one would expect
the ratio of the two Cp's to be (4R)/(2.5R) = 8/5 = 1.6 .
I also have never heard of this "alternative convention", described in footnote 2, according to which a
degree of freedom is counted in each direction. Unless someone comes up with a reference for this, I'm
going to get rid of it.--
Rparson 22:40, 11 December 2006 (UTC)
'The standard pressure was once virtually always “one standard atmosphere”...' What in God's name is this supposed to mean? Edison 21:44, 22 January 2007 (UTC)
the article indicates that the specific heat of water is in the unit joules per kelvin per kilogram- yet the chart indicates that the specific heat of water is in joules per kelvin per gram. Which is correct? —The preceding unsigned comment was added by 75.8.123.248 ( talk) 03:21, 1 March 2007 (UTC).
Would you define 'S' please.
Qskeptic —Preceding unsigned comment added by 203.101.236.10 ( talk) 07:01, 27 May 2008 (UTC)
Sorry to respond 6 months after the fact. By suggesting we should report all values in SI units, I don't mean "scientific notation" -- I mean SI units, as in the International System of Units established, maintained, and kept current for over 40 years by the National Institute of Standards and Technology (NIST). SI units are the "basis of all international agreement on units of measurement," according not only to the NIST, but to Wikipedia's own page on the Metric_system.
Every discipline defines their own units best suited to communicating within that discipline. E.g. meteorologists rarely express pressure in the derived SI unit "pascals" because the "P" in "STP" is 101,325 Pa. Besides, the math is a lot easier if P = 1 atm.
But everyone contributing to this page, and trying to learn from it, will have a different lexicon depending on their background, so we should adopt the universally agreed upon convention to minimize confusion. Those who've grown accustomed to discipline-specific units are typically still aware of and conversant in the SI equivalents. And anyone who is trying to learn this material, must see it first in SI untis, to understand how it connects to the broader framework of general physics. Todd Johnston 22:36, 3 March 2007 (UTC)
Count Iblis ( talk) 23:43, 24 April 2008 (UTC)The introductory chapter of the book includes a discussion of units, but nowhere is mentioned the fact that the whole point of units is that you can choose whatever units are most convenient, such as using the (reduced) mass of the electron as a unit of mass in atomic physics.
Spiel496: Regarding this edit you made, I don’t understand why we are interpreting the meaning differently as I see you are a physicist. Maybe I'm wrong but it seems like simple reading. Note what Physlink’s Glossary says about the term. Search on the following text string to go to the relevant section: “Specific. In physics and chemistry”. PhysLink defines “specific” as follows:
“ | Specific: In physics and chemistry the word specific in the name of a quantity usually means ‘divided by an extensive measure; that is, divided by a quantity representing an amount of material. | ” |
Also, it seems that the opening definition in Intensive and extensive properties is clear as glass. It says
“ | [A]n extensive property of a system does depend on the system size or the amount of material in the system. | ” |
Clearly, measuring two grams of water produces a different value for the amount of heat energy required than does measuring just one gram.
The same Wikipedia article goes on to describe intensive measures. It says…
“ | [A]n intensive property (also called a bulk property) of a system is a physical property of the system that does not depend on the system size or the amount of material in the system. | ” |
(my emphasis).
An example of an intensive property would be viscosity, the value of its measure is independent of sample size until you get down to microscopic amounts.
Why do you think specific heat capacity is an intensive measurement? Greg L ( my talk) 00:05, 28 July 2007 (UTC)
The following text had incorrectly been in the Specific heat capacity article for 229 days:
“ | For liquids and especially solids in mechanical thermal applications, sometimes the specific unit-quantity is chosen as volume, and in this case the term volume-specific heat capacity or volumetric heat capacity is then used, and a subscript v is added. | ” |
The above text had been added, even though the following chart (and related text) had been in the article for months prior:
Under constant pressure |
At constant volume | |
Unit quantity = mole | Cp or CpH | Cv or CvH |
Unit quantity = mass | cp or Cph | cv or Cvh |
Please note that in the above chart, Cv and cv denote that a measurement was a constant-volume measurement of either a specific-mass or specific-molar quantity, not a “specific-volume” quantity. The alternative to a constant-volume measurement is a constant-pressure one (either Cp and cp). Accordingly, the following editors note (<!--text-->) was added to the “ Unit quantity” section:
“ | NOTE TO EDITORS: Please note that the subscript “v” in the symbol for specific heat capacity denotes that the value was a constant-volume measurement of a quantity expressed in terms of either mass or moles. It does not denote that the quantity was a “specific-volume” measurement. Please read the section of this article titled “Symbols and standards” and its paragraph regarding constant-pressure and constant-volume measurements. Although specific heat capacity may properly be converted and communicated in volume-specific terms for convenience in a particular application, it would be unscientific to measure and publish unit quantities for specific heat capacity in volumetric terms because a material’s density and thermal coefficient of expansion introduces two additional variables when converting to volume and when compensating to another thermodynamic condition. Too, precision would necessarily have to be reduced for materials with highly variable densities such as brick, stone, and wood. | ” |
Greg L ( my talk) 19:08, 3 August 2007 (UTC)
As Greg L continues his editing rampage (in a good way) I'm curious to know his opinion, and anyone else's, on merging this article with heat capacity. It was brought up earlier on this page, but not discussed. All the interesting stuff in this article would be just as relevant in the heat capacity article or vice-versa. The only thing that distinguishes the two topics is the fact that "heat capacity is proportional to the amount of material". That statement is not interesting enough to warrant a second article. Spiel496 01:24, 4 August 2007 (UTC)
Seeing no objections, I redirected Heat capacity to Specific heat capacity#Heat capacity and removed the merge templates. ← BenB4 11:42, 12 August 2007 (UTC)
The two tables of specific heat capacities look very out of place, right in the middle of the article. You're talking physical theory and nomenclature one minute and then all of a sudden it switches to building materials? (Seriously. WTF? Didn't have the time to figure out who added the latter list from the history.) Even the first table could do with some explanation of why it's placed there.
There's another list under Orders of magnitude (specific heat capacity), which has different substances listed. Might it be an idea to move/merge these two there instead? (And provide a short paragraph linking to said article.) — Liyang 02:20, 1 September 2007 (UTC)
Was Joseph Black a physician or a physicist? Bewp 13:53, 9 September 2007 (UTC)
I believe this is a pseudo-question, in the sense that in the XVIIIth century there was no such a thing as a "physicist", at least in the same sense we nowadays understand it. There was no formal, regular university education for Science in general (even the term "scientist" comes a lot later) - hence most scientists from the period had a background in Medicine or else.
How to title these folks in nowadays articles has always been a tricky thing. Many authors prefer to state them simply as "thinkers". However, in many cases, as in Joseph Black's, the bulk of the work refers to one or two nowadays well established disciplines, such as chemistry and physics, so regardless of his previous background one could title him a physicist, if you want to, or a scientist, if one wants to encompass his also important contributions to chemistry, for instance. Nevertheless, many authors would rather, perhaps for the sake of historic correction, state his formal education background - and hence the title physician.
Beto Pimentel (
talk) 11:19, 2 April 2008 (UTC)
I think this article is rather confusing. In my coursebook on physics, specific heat capacity and (normal) heat capacity are treated as two different physical quantities (which I think is correct), while in this article I do not get a grasp on what the difference is. The "specific heat capacity" should I think always be written with a lowercase symbol while "heat capacity" is written with an uppercase symbol . In this article, this is confused and not consequently done - I'll try to fix this. Also, the first formula that you see on the Specific heat capacity article, is the normal "heat capacity" definition.
To explain both quantities in one article seems to me like explaining heat and energie in the same article, or length and weight. In my opinion, they should again be splitted into two separate articles. There is some overlap, since the difference will be explained in both articles, but merging the two adds up to confusion. I'd like to hear other opinions before I do this. Anoko moonlight ( talk) 14:50, 21 December 2007 (UTC)
Ok there is something I don't get about rotation of diatomic gas on the z axis (rotation around the axis of the molecule) if the wave function is cylindrical (which is true I suppose -but i am not sure- for diatomic gases such as H2), then there is no rotation possible.I mean that if the molecule has perfect indiscernibility through rotation on itself, you cannot talk about rotation. The rotation is not frozen out, it is not a rotation at all since you get the same object when you rotate it. When user says "Electrons in any atom can gain angular momentum, so options to rotate more are frozen out but never absent)", what is meant by "electron gain angular momentum" ?
By the way would not it be the same problem for monoatomic gaz? if the "electrons can always gain angular momentum", then we could say that the sphere (monoatomic gaz) can turn on itself and you should consider 3 degrees of freedom of rotation for monoatomic gaz which I have never heard of (of course they would be frozen as well I know that, I just want to know what happens theoretically if you could go at whatever temperature you wanted...).
Now I know that in most molecules, there will be P-orbitals that are not invariant through rotation. But what if there is only S-orbital that are available? Is that impossible?
Basically all this is why monatomic gases show no signs of "rotating". What would rotate? The individual electrons either have angular momentum or not, and changing it for each one comes with an energy price. You can't rotate the singe monatomic gas "atom" without making it equivalent to electrons increasing angular momentum, and that's already fixed. S B H arris 10:55, 7 September 2008 (UTC)
What makes certain "minima" and "maxima" "notable"? at first, i thought these might be the highest and lowest heat capacities in the table, but this is not the case. and are the bold numbers "notable" as well? in what way? The answers to these questions should be included with the table. in its current state, the colors and bold numbers are just confusing.-- Jmjanzen ( talk) 16:10, 23 May 2008 (UTC)
How come there's no mention of how the specific heat is related to the partition function? —Preceding unsigned comment added by 83.216.146.141 ( talk) 13:34, 15 July 2008 (UTC)
I just moved this section down below monatomic and diatomic gases, and gave a linear polyatomic example for N2O. It many not be enough but it's a start. I think this fleshes out the gas part somewhat better. The sections treating actual heat capacity for molecules n >3 perhaps deserves more separaton from the discussion of quantum freezing out of modes. S B H arris 02:13, 4 June 2009 (UTC)
I'm going to change the representation of the coherent derived units in this article to division (using solidus) versus negative exponents. SI allows either to be used, but Wikipedia (which doesn't require SI anyway) specifies to use the most understood form when writing to a general audience. Since a person generally learns the mathmatical concept of division prior to learning exponentals (and certainly prior to learning negative exponentals), more people in the general audience of this article will understand unit representation via division. 66.19.201.92 ( talk) 18:39, 2 July 2009 (UTC)
The specific heat capacity of diatomic gases should be 7/2 R, but since the vibrational mode is frozen out most are less than 5/2 R. Presumably this is becasue the rotational modes are partly frozen out, but this is not explained. What puzzles me is why Br has a specific heat greater than 7/2 R. Could someone explain that? A B McDonald ( talk) 13:47, 22 July 2009 (UTC)
Values for Bromine were wrong - now fixed A B McDonald ( talk) 14:24, 22 July 2009 (UTC)
The article says the specific heat of water is 4186 Joules per kilogram, but cites a website which may not be reliable. A more reliable one, such as wolfram alpha which has all its data checked by real scientists, says it is 4.18 Joules per gram, and if it were 4186J/kg surely wolfram would have written it as 4.19J/g? —Preceding unsigned comment added by RLakshan ( talk • contribs) 09:26, 17 August 2009 (UTC)
Under: Symbols and standards
Water (liquid): cp = 6.1855 J/(g·K) (25 °C), and… ...
Table of specific heat capacities:
Water at 25 °C liquid Cp = 4.1813 J/(g·K)
The 2 figs in italics refer to the same constant, however they differ on the same page.
I think the error is in the former, the latter being the correct figure.
Tks
—Preceding
unsigned comment added by
121.7.177.137 (
talk) 13:26, 14 October 2009 (UTC)
Hi, if that the case then maybe anonymous free editing shouldn't be allowed. Anonymous users should however be allowed to 'discuss' wanted changes so that a registered moderator can make the necessary amendment. Case in point here about lax rules and the significant damage/ deception vandals can cause. Spiel496, thanks for the prompt correction. (Fr author of 1st msg w 'floating IP address') —Preceding unsigned comment added by 219.74.223.200 ( talk) 20:17, 14 October 2009 (UTC)
The terminology here is inconsistent both internally and with usage "in the wild", where there is also inconsistency. In particular, use of the term "specific heat" appears to predate the use of "specific heat capacity" as used in this article. I have two college physics textbooks by Robert Resnick and David Halliday, (Resnick, R. and Halliday, D.; _Physics, Part I_; 1966) & (Halliday, D. and Resnick, R.; _Fundamentals of Physics_, 1970) that define specific heat as "heat capacity per unit mass". Earlier college physics textbooks (I have Hausmann and Slack, _Physics_ (2nd ed.); 1939) and (Spinney, L. B; _A Text-Book of Physics_ (3rd ed.); 1925) that both define "specific heat" of a material as the ratio of the heat requried to raise the temperature of the material by one degree to the heat required to raise the temperature of water by one degree. A starting water temperature of 15°C is implied. Dictionary definitions, plus my 1975-76 CRC Handbook of Chemistry and Physics agree with this definition of "specific heat" as a unitless ratio.
To further complicate things, the CRC handbook agrees with Hausmann & Slack in defining "thermal capacity" to mean what this article calls "specific heat capacity", while the older Spinney book uses the same term "thermal capacity" to mean what Resnick, Halliday and this article refer to as "heat capacity"--a property of an object, not a material.
Reading this article, there are regular references to "specific heat" in the Resnick/Halliday sense of dQ/(m dT) or "heat capacity per unit mass". The Wikipedia article on Calorimetry uses "specific heat" to mean the same thing. Eric Weisstein's "World of Physics" (hosted by Wolfram Research at http://scienceworld.wolfram.com/physics/SpecificHeat.html) also lists specific heat as the primary term, noting that it is "also called specific heat capacity".
Maybe these modern writers are shortening the longer "specific heat capacity" term, but it seems unlikely that Resnick and Halliday were. It seems to me that some citation is needed here. When did the terms "specific heat capacity" and "heat capacity" become *the* terms in the senses used here, and by what authority. Husoski ( talk) 06:06, 14 November 2009 (UTC)
The older way of using the word specific is as a clue that something was being compared to some standard, like water, by further comparing the previous number to the corresponding one for water. And thus, you obtain a "water-specific heat capacity," which is dimensionless. The number 0.5 simply means it has 50% of the corresponding figure for water, but to get the units you have to see what they used for the water.
This is confusing because sometimes the WORD "water" is left off, so you have to know the reference to water is implied, if no units are given. The same thing happens with "specific gravity": it's really "water-specific gravity," and it's unitless. Something with a "specific gravity" of 9, that means it has 9 times the density of water, but no units are given unless you use the units you meansured density in, with water (mass per volume). Acceleration is sometimes measured in units of g's, and then it's "g-specific" acceleration and you have to know the units of a standard g. The older use of "specific" as comparing to some standard other than one involving an SI unit, is dying away. Nowadays, "specific" almost always means you divide by a new SI unit which relates, directly of indirectly, to amount of material. Water comparisons are out. Oh, yeah, sometimes even then they use the word specific, and don't tell you WHAT is the unit being used for the comparison. They say specific and mean "mass-specific." Since you might think volume or mole-specific, that's bad form. S B H arris 08:30, 18 November 2009 (UTC)
The given value is erroneous. I think it is the value in cal/g/K and I proposed a value of 1700 J/kg/K. It is not a precise value, being subject of variation with different types of wood and with humidity. I do the same correction in the french wiki page, with the same table translated from english page. A concluding remark for anybody who want to complete the talk : the german wiki page on the same talk is well documented.-- Jean-Marc.Vignon ( talk) 08:00, 24 November 2009 (UTC)
the compare for the climate change of sea water and air. —Preceding unsigned comment added by 67.115.155.131 ( talk) 19:58, 7 December 2009 (UTC)
The heat energy required to raise water’s temperature one kelvin per kg is given as 4186 Joules per kilogram in the first couple of sentences but in the table is listed as 4.1813 J/(g*K). This is not consistant. 1 kg of water is not exactly equal to 1000 cm^3. Hcbonner ( talk) 16:30, 14 December 2009 (UTC)
The article states that the specific heat capacity of water is 4186 J/kg (3rd line from the top). This is wrong. The specific heat capacity of water is a function of temperature, fitting closely the following equation: Cp water(liq) = -1.0545E-04(T^3) + 1.1554E-01(T^2) - 41.296T + 9018, where T = degrees K. The Cp decreases from a value of 4210 at 273.16 K to about 4178 at 308 K, then it goes back up to about 4219 at the bouling point (373.15 K). Thus there are actually two temperatures where Cp = 4186. There are many references giving the actual numbers for Cp of liquid water as a function of T. Can somebody please edit the article to correct the error? Thermbal ( talk) 20:53, 9 January 2010 (UTC)
Is there a link to how to calculate the specific heat capacity of alloys, such as brass or mixed materials such as humid air? This might be interesting especially for the construction and HVAC industry active in continental, maritime and tropical climates. —Preceding unsigned comment added by 202.82.143.78 ( talk) 03:34, 12 January 2010 (UTC)
The note to editors claims that there is ambiguity about the unit quantity in specific heat? Where is that found? As far as I know, specific heat capacity (or anything specific to that matter) always refers to property/mass. For a unit quantity of mole, the name is molar. —Preceding unsigned comment added by Alexander.mitsos ( talk • contribs) 23:30, 17 February 2010 (UTC)
That is right. Although it turns out that many "specific" quantities are intensive, not all of them are, or else I would have said so. "X-specific" really does mean, in general, "per X", which means you divide by X. Specific impulse can be a real intensive quantity (impulse per mass), or it can be oddly expressed as an impulse (momentum change) per earth-weight, which isn't the same thing at all. Dividing by weight (making it weight-specifc) doesn't result in an intensive quantity, since you may be someplace in space where things have no weight, but you divided by mg instead of m, anyway. You've then just divided by earth g for no good reason. It's still called "specific-impulse" however, even if you express it in seconds, which means with the extra Earth-acceleration-division. A better example is the well known thrust specific fuel consumption of an engine. It has units of grams/sec of fuel the engine consumes per kilonewton of thrust. Hence the term "thrust-specific" not mass-specific. It's a specific but not in any possible way, an intensive quantity. The inverse of it is vaguely intensive (sort of, almost), but you see the point. We're not talking about its inverse. S B H arris 06:40, 25 February 2010 (UTC)
That some elementary quantum theory is necessary to calculate heat capacities, is an undergraduate textbook subject. For example, my own (dated-- 1966!) copy of W. Kauzmann's Kinetic Theory of Gases, has a full chapter on it. He not only treats the easy cases where the equipartition theory asigns the full R/2 heat capacity per degree of freedom in gases (with a guess as to which degrees will be fully excited and which fully frozen out) but also treats the harder cases in which either rotational or vibrational modes are only partly participating, so that heat capacities are intermediate. Example: chlorine has a Cv heat capacity of 2.5 R if no vibrational modes are exited, and 3.5 R if they all are. The observed value for 25 oC is 3.1 R in modern sources, (2.9 R in the heat capacity article, which needs changing; but 4.1 for Cp = 3.1 Cv in the clorine article)-- right in the middle of these two equipartitial values. The quantum theoretical value (from Kauzmann) assuming partial excited vibration is 3.1 R, which is better that his experimental data (which is 3.0 R). Evidentally, though, these things come out fairly well. I can give other examples in a table as Kauzmann does, and perhaps should.
Now, user:Kbrose has worked to remove all mention of quantum effects in the LEDE, saying (in the diff) "quantum theory is not used to predict thermodynamic systems, semiempirical methods are hardly successful." Rather than argue with somebody who does not know what he is talking about (this is not an expression of bad faith, it is a self-evident fact) I'm going to put the matter here and in some chem-group talk pages, and let you all tell him what I just did. Perhaps he'll listen to some of you. S B H arris 00:33, 25 February 2010 (UTC)
Material written by sbharris and copied from kbrose talk page:
In the article on specific heat capacity you have written:
Temperature is the result of the average kinetic energy of particles in matter, usually referred to as thermal energy in thermodynamics. Heat is transfer of thermal energy; it flows from regions of high temperature to regions of low temperature. Thermal energy is stored by matter as potential energy in the modes of vibration, representing degrees of freedom of movement. Each degree of freedom contributes to the heat capacity of a thermodynamic system.
The first part of the first sentence is true, the second part is not. Thermal energy is not temperature; it is energy content. Thermal energy is also not kinetic energy, either-- in a solid only 50% of the thermal energy is kinetic energy, and other 50% is potential (excluding any odd storage in subatomic degrees of freedom like electronic excitation, nuclear magnetic effects and so on). The only place thermal energy is kinetic energy, is in monatomic gases! Thus, the third sentence is also wrong (unless you qualify it in that sense). Finally, the last sentence is also wrong without qualification: it is quantum mechanics which tells us whether any given degree of freedom contributes to heat capacity, and how much. Some contribute nothing at all (as for example in many gases at room temp). Your edit diff says: "This whole paragraph is such poor science, movable energy? quantum theory is not used to predict thermodynamic systems, semiempirical methods are hardly successful." First of all, the definition of heat is "the process of energy transfer from one body or system due to thermal contact," so what's poor science about saying it's "movable energy"? If you don't like the term, replace it with "transferrable energy due to thermal contact." Second, quantum theory is indeed used to calculate many heat capacities, and to very good result. I'm not talking about general thermodynamic systems, I'm taking the thermodymic property which is the topic of THIS article. In fact, the quantum calculations are excellent for predicting heat capacities for gasses, even in temp ranges where some degrees of freedom are only partially excited (including prediction of what those will be for any given molecule), and even in solids, the Debye theory provides reasonably good numbers for crystalline insulating solids at low temperatures. Out of curiousity you have a Ph.D. in WHAT? S B H arris 23:12, 24 February 2010 (UTC)
Kbrose ( talk) 23:49, 24 February 2010 (UTC)
Of course Debye theory is a quantum theory. A "phonon" is by definition a quantum "object"-- specifically a quantum of vibrational energy. Any theory of mechanics that uses Planck's constant is necessarily a quantum theory. Maybe not one that uses the Schroedinger equation, but that doesn't mean it's not QM.
If you had trouble with the fact that quantum theory works well only with gases (which of course there are a great many, and many, many cases) and in some kinds of solids at low temperature, you could have put that. Not delete the thing entirely. It's also a little unfair to imagine that quantum theory doesn't work with solids at higher temperatures, since it gives the same predictions as classical theory for most solids, and for those that don't fit classical theory, like diamond or beryllium, quantum theory tells us why.
I got the 50% from the obvious fact that thermal energy in solids is stored in 6 degrees of freedom to give the Dulong-Petit heat capacity of 3R per mole/atoms. If it was all kinetic energy, as with a monatomic gas, it would obviously be just half as much. You are completely wrong about thermal energy. The whole point of heat capacity is that when systems are in contact, they transfer their entire thermal energy, including that stored as the 50% of vibrational energy which is vibrational potential energy (the other 3/2 R in a solid which is NOT vibrational kinetic energy). Objects on a spring have half their energy as kinetic and half potential (on average). Adding up many small objects, and this averages out to 50:50. You are the one confused about "internal energy," a concept that includes many other kinds of potential energies (bond energies and such) that aren't transferrable as heat, and so do not contribute to either thermal energy or heat capacity (not relevant).
It's rather incredible to me that although you understand that temperature has to do with kinetic energy only, you do not understand that this kinetic energy is in contact with other reservoirs, so that thermal energy can be stored in many other ways in most substances (certainly all but monatomic gases), and so these other ways of storing energy much be taken account of, in order to get numbers for heat capacity. Had you read and understood the paragraph you removed discussing this, you actually might have learned something there. Too bad.
You didn't answer my question about your Ph.D. S B H arris 01:19, 25 February 2010 (UTC)
I'm not confusing internal energy with anything. You brought that term into the discussion, and it has nothing to do with heat capacity. Thermal energy does have everything to do with heat capacity, but THAT term includes potential as well as kinetic energy for solids, in contradition to what you wrote. I simply tried to point that out, and ran into obfuscation. Get over it. And yes, I think it goes without saying that heat transfer stops when temperature difference drops to zero. Do you really think that I, or anybody else here, thinks differently? However, so long as heat is transferred, it includes the part of heat-energy that is vibrational potential energy, in all substances except monatomic gases. Simple enough. S B H arris 06:55, 25 February 2010 (UTC)
This defines the heat capacity at constant volume. I'd be curious to know what you think U stands for, if not the internal energy. And if you can't accept simple references, you might want to compare this with Richard Feinman's Lecture on Physics. I am sure he has better skills to convert you than I do. Kbrose ( talk) 17:09, 25 February 2010 (UTC)
Actually, however, let me add that although Feynman is not wrong, there are other definitions for absolute “internal energy,” which is a poorly defined quantity if you make the mistake to attempt to define it as other than a “perfect differential” dU or dE (which is the only way it’s actually defined, without any question, in thermodynamics). Feynman’s definition of U is one of many, but it doesn’t matter, since he never uses U again, but rather the differential form. Feynman’s equations above (from chapter 45) involve differentials, not absolute U or E or Q. The fact that dU = dQ certainly does not imply that U = Q, because there’s a constant of integration there to ruin things, since you can set it to any value you like. Thus, if we remove (essentially) all the heat content from an object by cooling it to (essentially) absolute zero, that does NOT imply that its “internal energy” is necessarily now zero! You can decide what it is, because that's the integration constant. This internal energy at absolute zero actually has a name: it is called “zero point internal energy.” It includes some atomic kinetic and potential energies, because atoms are never still. And other energies as well, if you want to count rest energies of atoms, subtract negative contributions of bond energies, and so on. Which is why internal energy doesn't work to calculate heat capacities, but changes in internal energy does (a change in any kind of energy, due to heat, can works to define heat capacity: but you use dQ/dT = Cv = [1/c2]*(dm/dT), which is true, that doesn't prove mass really has anything to do with heat capacity; rather, it's the CHANGE in mass).
If you wanted to define E_zeropoint or U_zeropoint as being 0, nobody would care, because in thermodynamics, it’s mainly the Gibbs differential equations that count. With the exception of entropy, nobody cares about the “absolute value” of state functions very much, since for internal energy the absolute value is hard to define, because it depends on what things (what bonds and rest masses and so on) you want to include. [3].
Anyway, the poor state of the wiki on internal energy (which again is not heat content just because if you add heat, it changes by the same amount) doesn’t suggest these problems, but reflects the depredations of user: Sadi Carnot, who has been scarce since being identified as a socker in Oct. 2007. Sadi also had the idea that every single thermodynamic term had a single and correct definition, and that one was the one he liked. Perhaps it’s time, with the stimulus of assertions by Kbrose, to undo some of the damage that was done to the thermodynamics articles 3 years ago. S B H arris 02:16, 26 February 2010 (UTC)
In his zeal to make us all believe the fiction that "thermal energy" in solids is a total of kinetic energy, we have an editor who has added cites 4 and 5. Although WP:RS deprecates web and self-published sources, and encourages scholarship which is to say, "published in reputable peer-reviewed sources or by well-regarded academic presses," instead we get a commercial dot.com website run by http://www.ronkurtus.com "School for Champions". Last publication: Tricks for Good Grades: Strategies to Succeed in School. And let's hope Ms. Teacher doesn't know much quantum theory of heat capacity.
For grins, I cannot resist giving some of what this website says about thermodynamics:
Thermal Energy is Total Kinetic Energy by Ron Kurtus (revised 22 March 2007): The thermal energy of an object consists of the total kinetic energy of all its atoms and molecules...The Kinetic Theory of Matter states that matter consists of atoms or molecules in random motion. Those moving particles can transfer their kinetic energy to other nearby particles. The total kinetic energy of all the particles in an object make up the thermal energy of that object.
"The kinetic theory of matter"? Bet you never heard of it. That's because Kurtus just made it up. And if you can't figure out why he doesn't don't know better, there is a quote about this here series, asserting that he knows better than the texts:
Heat is the movement of molecules. It is the sum of their kinetic energy. In many physics textbooks, they look at heat as some sort of substance and heat energy as something independent of kinetic energy. In our lessons, it is just another form of kinetic energy.
So, it doesn't matter if our lessons are wrong. They're our lessons, and we're sticking to them. :0
And finally a definition of thermal energy that includes the kinetic energy of electrons, protons and neutrons:
This motion is the culmination of the constant little movements, wiggles, jiggles, and vibrations of those atoms and molecules that make up this human. In describing the capacity of all this atomic and molecular movement to do work, physicists refer to it as thermal energy. Remember, energy is defined as the capacity to do work. These constant wiggles, jiggles, and vibrations are called translational, rotational, and vibrational movements. If we move further down the scale, thermal energy is the culmination of the kinetic energy of the movement of the constituent parts of an atom (electrons,protons, and neutrons).
. Bet you didn't know thermal energy included the movement of consituent neutrons in atoms.
I've put a unreliable source? template on this source. Rarely have I encountered a science "source" on the web that needed it so badly. S B H arris 08:44, 25 February 2010 (UTC)
Feynman's name has been misspelt in ref.6 (spelt as Feinman) —Preceding unsigned comment added by 202.56.7.137 ( talk) 14:29, 15 April 2010 (UTC)
Why on earth don't we have a proper article on Heat Capacity ?
At the moment anyone looking up Heat Capacity gets redirected to Thermal mass -- which I suppose is indeed a synonym for heat capacity used in the building trade; but certainly shouldn't be our main article on the subject.
I understand that there was a merger a while back; but surely the primary quantity here is the heat capcity. That's the one that turns up again and again as in fundamental thermodynamical equations as CV and CP. Specific heat capacity is a derived quantity, obtained by deriving the fundamental extensive quantity by the mass.
I came here looking for how WP treats negative heat capacities, for instance as found for gravitational objects like stars, and also black holes. Instead, I was surprised to find we evidently now don't have a self-standing article for heat capacity at all.
I also note that molar heat capacity currently redirects here.
If we're going to have a single article to cover heat capacity, molar heat capacity and specific heat capacity, then it's name should be heat capacity, and it should be written as such.
I therefore propose a move to heat capacity as the main title for this article, over the current redirect. Jheald ( talk) 14:21, 23 April 2010 (UTC)