Talk:Calorimetry

Comments

The following sections are tangential to the subject of calorimetry. --[[User:Eequor|η♀υωρ]] 15:12, 18 Sep 2004 (UTC)

I notice this unusual structure of subsections in this section. What are the differences in wikimark-up?--5.2.200.163 (talk) 10:22, 22 October 2015 (UTC)

I am sorry I have no inkling of what you are talking about here. Please, if you are willing to clarify, would you very kindly do so in a new section at the bottom of the page. The section you have added to here was 11 years old, and I regard it as obsolete. It is customary to add new comments at the bottom of the page.Chjoaygame (talk) 13:17, 22 October 2015 (UTC)

Heat

Main article: Heat.

Heat is an amount of energy which is usually linked with a change in temperature or in a change in phase of matter. The SI unit for heat is the joule.

The equation for measuring heat is:

$q=C\Delta t\,\!$

• q is heat. When heat transfers energy from the system to the surroundings, the symbol is -q. When heat transfers energy from the surroundings to the system, the symbol is +q.
• C is heat capacity.
• Δt is change in temperature.

Work

Main article: Mechanical work.

Work is the energy transferred in applying force over a distance. In calorimetry, the force is generally pressure and instead of distance, volume is used. Work is given by the formula:

$w=-P\Delta V\,\!$

• w is work. When work transfers energy from the system to the surroundings, the symbol is -w. When work transfers energy from the surroundings to the system, the symbol is +w.
• P is the pressure of the system.
• ΔV is volume change.

Internal energy

Main article: Internal energy.

Internal energy is the kinetic energy associated with the motion of molecules, and the potential energy associated with the rotational, vibrational, and electric energy of atoms within molecules. Internal energy is a quantifiable state function of a system.

Internal energy can not be measured directly; it is only measured as a change (ΔU). The equation for change in internal energy is:

$\Delta U=q+w\,\!$

Enthalpy

Main article: Enthalpy.

Enthalpy is the sum of the internal energy of matter and the product of its volume and the pressure.

Enthalpy is defined by the following equation:

$H=U+PV\,\!$

• U is the internal energy.
• V is the volume.

The total enthalpy of a system cannot be measured directly; the enthalpy change of a system is measured instead. Enthalpy change is defined by the following equation:

$\Delta H=H_{final}-H_{initial}\,\!$

• ΔH is enthalpy change.
• H_final is the final enthalpy of the system. In a chemical reaction, H_final is the enthalpy of the products.
• H_initial is the initial enthalpy of the system. In a chemical reaction, H_initial is the enthalpy of the reactants.

Parr History

It appears the history alluded to in the article [at the bottom] is the history of a company that makes lab products, not a history of calorimetry. In fact, when I looked at the history page, I saw almost nothing pertaining to the history of calorimetry?

Is it possible someone just wanted free advertising? Should we snip it?

Phantym 21:24, 24 May 2005 (UTC)

temperature of an isolated object

The article currently claims If an object is isolated from the rest of the universe, its temperature must stay constant.

I suspect this is incorrect. If I take this small, inert rock at room temperature, and stick it far out past the orbit of Pluto, its temperature would plummet, right? What about the heat pad mentioned in the supercooling article? Imagine that I pull the pin from a grenade, then isolated that grenade from the rest of the universe. The temperature of that grenade rapidly rises when it eventually blows up, right? --DavidCary 03:33, 22 September 2005 (UTC)

Wrong --Dan|^(talk) 09:37, 15 March 2006 (UTC)

I think DavidCary has a point, although his rock example isn't right. I think that the missing part of If an object is isolated from the rest of the universe... is that the system must be at equilibrium within itself. The grenade example given shows that a system that is out of equilibrium can change temperature. Perhaps more transparently, if we imagine two reagents for a reaction seperated by a diffusive membrane, if we place this system in a calorimeter, it will naturally change temperature (assuming the reaction is exo/endo-thermic). Isothermal titration calorimetry for instance requires heat to be transfered between the system and a resevoir in order to keep the temperature constant. Remember that energy is conserved, not temperature. Zvsmith 16:08, 12 December 2006 (UTC)

Calorimetry of a 'multi-state' system?

If a system has several energy states at a given temperature, calorimetry can be used to dissect the number and energy of the different states, right? That would be a nice thing to add here. --Dan|^(talk) 09:38, 15 March 2006 (UTC)

I got some references here (specific to protein folding / folding intermediates), which may be a start for this section...

• Freire, E. 1989. Comments Mol. Cell. Biophys. 6:123
• Freire, E & Biltonen, RL. 1978. Biopolymers. 17:481
• Fieire, E & Biltonen, RL. 1978. CRC Crit. Rev. Biochem. 5:85
• Freire, E et al. 1990. Annu. Rev. Biophys. Biophys. Chem. 19:159
• Privalov, PL. 1982. Adv.Protein Chem. 35:1

HTH --Dan|^(talk) 09:58, 15 March 2006 (UTC)

flow calorimetry

Any objections if I add a paragraph on flow calorimetry? I'll put a draft in discussion, or on my talk page before adding it. Alanf777 (talk) 18:04, 28 November 2011 (UTC)

No objection from me. Sounds good. Reliable sources. Here is good page for discussion.Chjoaygame (talk) 21:41, 28 November 2011 (UTC)

I decided I didn't know enough about it! 71.139.166.65 (talk) 21:06, 23 January 2012 (UTC)

Well, that you are able to say that you don't think you know enough about it, that tells me you are likely to be a good scientist and editor. I look forward to your work when you are ready.Chjoaygame (talk) 22:31, 23 January 2012 (UTC)

This is not a good description of CALORIMETRY

The page on CALORIMETRY is not good. It is far too theoretical and will only serve to scare people away from calorimetry. There are at least a dozen different calorimetric techniques (DSC, adiabatic calorimetry, semi/quasi-adiabatic, heat conduction, radiation detectors, flow calorimetry etc etc) that need to be described at the start so that the reader can decide which technique he/she is interested in. Now - after a few lines of general information - the reader meets a complex text and a lot of math which is complex and very limited with respect to what calorimetry is in general. For example, after the figures the text is "Calorimetry requires that the material being heated have known definite thermal constitutive properties...". This is not true for at least two reasons: 1. In most calorimetric techniques the sample is not heated. 2. Calorimetry is just a collection of measurement techniques; they work - more or less well - on all materials. One of the advantages of the calorimetry (heat conduction) that I work with is that it is not dependent on the properties of the samples (solid/liquid/gaseous, transparent/opaque, surface area etc). I have worked with calorimetry for about 20 years and I have never used the equations that make up 95% of this page. I may come back and try to do something here when I have time, but I do not know where to start... . — Preceding unsigned comment added by Larswa (talk • contribs) 13:23, 2 March 2014 (UTC)

It will be good to have your expertise here. We look forward to your contributions. I have made one edit that intends to comply with your concern that "In most calorimetric techniques the sample is not heated".

Your practical knowledge will be invaluable. I would say, however, that there is some value in the presentation here of the classical theory of calorimetry that you say will scare people away. The classical theory has a relationship with thermodynamic theory that I think is worth reporting in this article.Chjoaygame (talk) 14:08, 2 March 2014 (UTC)

One comment to my own posting: why are the pages for CALORIMETRY and CALORIMETER so different?Larswa (talk) 16:01, 2 March 2014 (UTC)

Your guess is as good as mine. There is little rhyme or reason to Wikipedia structure. I don't recall examining the article entitled Calorimeter. I think it in general a good assumption that Wikipedia articles may be more or less inconsistent.Chjoaygame (talk) 01:28, 3 March 2014 (UTC)

undid good faith edit: reason

I undid this good faith edit. It was too specialized for the place where it went in the lead. Besides constant pressure calorimetry, there are also forms of calorimetry with constant volume, and with constant temperature.Chjoaygame (talk) 18:11, 21 October 2015 (UTC)

Nuclear calorimetry

I think a section about nuclear calorimetry is a very useful addition to article. This proposal is made given the aspects analyzed on talk:standard enthalpy of formation and talk:Hess's law especially about the heat of neutron capture reactions and its consequences on applying Hess law in calculating the heat of formation of isotopes like deuterium D(2) which seems to generate inconsistencies between various (standard thermochemical) assumptions like D2 heat of formation beeing considered zero by NIST tables.--5.2.200.163 (talk) 10:15, 22 October 2015 (UTC)

Because at present the article does not have such a section, I read you as meaning not that "a section about nuclear calorimetry is a very useful addition to article", but rather as meaning 'a section about nuclear calorimetry would be a very useful addition to article' [my italics]. I think a new section on this subject would need to be based on a fair survey of reliable sources. Part of surveying reliable sources is finding them. The concordant material of perhaps five reliable sources would be good, since there are many ways of thinking in thermodynamics. An editor who adds material should base it on such a survey that he himself has done. Perhaps Editor Dirac66 may have a view on this?Chjoaygame (talk) 13:35, 22 October 2015 (UTC)

As I have explained at Talk:Standard enthalpy of formation, the only "inconsistency" is that the small NIST thermochemical values imply that nuclear reactions must be excluded, whereas Editor 5.2.200.163 thinks they should be included. I am not familiar with the nuclear physics or engineering literature which may perhaps include nuclear reactions in the calculations. If we do find such sources, that would not mean that one way is wrong. Rather that there are two alternate conventions, presumably one in chemistry and one in nuclear science. Dirac66 (talk) 01:32, 23 October 2015 (UTC)

Several conventions are not excluded, but both calculations should be compatible with the use of Hess law. We could bring some editors here to start finding sources.--5.2.200.163 (talk) 15:52, 23 October 2015 (UTC)

It seems you are nominating yourself as an editor who will find sources. Welcome.Chjoaygame (talk) 18:28, 23 October 2015 (UTC)

I'll try to search some sources. We can ask other editors involved here on the talk page who have proposed some additions to article to join the search for sources.--5.2.200.163 (talk) 16:07, 30 October 2015 (UTC)

I observe above a comment from an editor who points out that the present article is rather, perhaps even excessively, theoretical, and then points out that there is also an article entitled Calorimeter, which is oriented differently, being about various calorimetric devices. Perhaps that would be the place for material about nuclear calorimetry?

Editor 5.2.200.163 (perhaps he might very kindly give himself a user name, chosen carefully to protect his privacy, and more pleasant for editorial chat) is concerned to put up something about nuclear calorimetry. Previous to his comment on this talk page, he has raised this question at Talk:Standard enthalpy of formation. Presumably he thinks it relevant there.

I think part of his concern seems to be with Hess's law. Would it be relevant there? In that article I seem to find what looks to me like a mistake. The lead there says "Hess's law is now understood as an expression of the principle of conservation of energy, also expressed in the first law of thermodynamics, and the fact that the enthalpy of a chemical process is independent of the path taken from the initial to the final state (i.e. enthalpy is a state function). It applies to the special case of paths consisting of chemical reactions (or changes of state) at constant temperature and pressure." I am puzzled by the quote's claim that the path must be at constant temperature and pressure. I think the tables put the initial and final states at specified temperature and pressure, but the quote, in places, says that the path is both definitively constitutive and irrelevant. According to Partington (1949): "Hess's Law is strictly true only when either (i) the volume or (ii) the pressure is constant, ..." (p. 152.). Also I think (every improvement makes things worse) that STP no longer has a pressure of 1 atm; the specified pressure is now 1000 hPa ? The article on Standard enthalpy of formation, in the lead, talks about a pressure of 1 atm for the standard state, not the same thing as the state at STP.

I have now noticed that there is already an article Calorimeter (particle physics). I suppose it would be relevant there, but perhaps not?

Looking at the present article here, Calorimetry, I think, for it, nuclear calorimetry would be a big change in direction, without an obvious reason. I don't have an opinion about how it would fit in the article headed Standard enthalpy of formation. Perhaps Editor Dirac66 would advise us on that?

Does Editor 5.2.200.163 have main aim here? If so, what is it?

Perhaps the topic needs an article of its own?

I guess the answers to these questions will be easier to find when we have a basis in reliable source material. The concerns of the sources may provide guidance.Chjoaygame (talk) 00:31, 31 October 2015 (UTC)

My opinion is that nothing should be inserted on nuclear calorimetry unless sources are given. Much of the above discussion is based on 5.2.200.163's opinion of what seems reasonable, but both Chjoaygame and I have presented objections to his/her reasoning, and Wikipedia policy is not to include disputed material without sources. I do not think it necessary to repeat the whole argument again.Dirac66 (talk) 18:02, 31 October 2015 (UTC)

Hess's law article wording of intro

Editor Chjoaygame has objected above to the sentence It [Hess's law] applies to the special case of paths consisting of chemical reactions (or changes of state) at constant temperature and pressure. I think this is just a case of sloppy wording. Chjoaygame has interpreted It applies ... as It must be at constant T and p, which I agree would be incorrect here. But I think what was meant is It is usually applied to, which just means that most applications of Hess's law consider the case of constant T and p for convenience, and does not imply that the law is invalid for other cases. I will change the wording of that article accordingly. Dirac66 (talk) 18:02, 31 October 2015 (UTC)

Perhaps my worry about words is over-fussy. I just wanted to say that the end-points are the concern of the law, not the paths. The wording seemed to me to stress the paths, and to say unintended things about them. As I understand it, during the course of the process, on the path, there is no restriction on temperature or pressure. Indeed I think that a path is not necessarily defined for law; the system is allowed to explode, just so long as it respects the end-points. It puzzles me why constant temperature and pressure lead to enthalpy, not the Gibbs function.Chjoaygame (talk) 00:18, 1 November 2015 (UTC)Chjoaygame (talk) 00:37, 1 November 2015 (UTC)

Point taken. Should we replace the offending sentence then with something like the following? Reaction enthalpy changes are usually given for paths with final conditions (temperature and pressure) equal to the initial values, but the conditions can vary during the reaction. Dirac66 (talk) 01:56, 1 November 2015 (UTC)

My instinct is that your judgment will be reliable for that page. As for the proposal Reaction enthalpy changes are usually given for paths with final conditions (temperature and pressure) equal to the initial values, but the conditions can vary during the reaction. I would replace the word 'path' with the word 'process'. I would make it into two sentences, without the "but". So Reaction enthalpy changes are usually stated for processes with the same initial and final temperatures and pressures. The conditions can vary during the reaction. But I defer to your judgment.Chjoaygame (talk) 03:38, 1 November 2015 (UTC)

Thanks. I have now inserted your version. Dirac66 (talk) 10:46, 1 November 2015 (UTC)

Oops, I have been careless and wrong here. We are stating Hess's law in terms of enthalpy. We are looking at a version of the first law. First, matter may neither enter nor leave the overall system. For enthalpy, the pressure is held constant throughout the processes. Heat transfer to and from a reservoir is allowed and recorded, the temperatures of the reactants during the reaction being allowed to vary. The volumes may vary and must then be recorded. PV work may be done, accounted for by the recorded changes of volumes at the fixed pressure. According to Partington, when the reactants are liquid or solid, the volume changes are usually small. When the reactions are finished, heat is made to pass to adjust the final temperature to the standard value, still at the fixed pressure, the PV work again being accounted for. (Alternatively, according to Partington, the law can be stated for fixed volume, pressure variation being allowed. Then the state function of interest is the internal energy.) My amended version would be Reaction enthalpy changes are usually stated for overall processes with the same initial and final temperatures and pressures. Heat is allowed to enter and leave the reactants, from or to a controlled heat source, the amounts being recorded. During the reactions, the pressure is held constant, the reactants' temperatures and volumes being allowed to vary, and being recorded, to account for heat and work. After the reactions, at constant pressure, a recorded amount of heat is made to enter or leave, to adjust the products to the standard temperature, the volume changes and work done again being recorded. Or perhaps what I wrote near the beginning of this paragraph would be better. Please excuse me, and check and readjust this as you think fit.Chjoaygame (talk) 15:50, 1 November 2015 (UTC)

I think these new versions (both at the beginning and at the end of the paragraph) are much too detailed for the intro to the Hess's law article. Instead I suggest that you insert one of them in THIS article (Calorimetry), perhaps as a section on Constant-pressure calorimetry or Condensed-phase calorimetry. This article now has a section on constant-volume bomb calorimetry, but not on constant-pressure calorimetry.

Then in the Hess's law intro, we can refer to this article for experimental methods, citing both the constant-volume and constant-pressure methods. For the constant-volume method, we can also point out that the calorimetry determines ΔU to which Δ(PV) must be added. Dirac66 (talk) 16:44, 1 November 2015 (UTC)

For the article on Hess's law, I didn't intend to get in this deep. I repeat, my instinct is that your judgment will be reliable for that page, I defer to your judgment, and please excuse me, and check and readjust as you think fit.

For the present article, the sub-section on constant-volume calorimetry is not concerned with Hess's law. It doesn't consider heat of reaction, which is a variety of latent heat. In the past, I overwrote a pre-existing practically oriented section into the present theoretically oriented sub-section, now I see as not a very good move, but made because I wanted to focus on pure classical calorimetry as logically prior to and not reliant on thermodynamical theory, in particular not reliant on the first law. Before I edited the article, and still now, there was and is no corresponding practically oriented section or sub-section on constant-pressure calorimetry. A significant difference between the earlier practically oriented section on bomb calorimetry and my overwriting theoretically oriented sub-section is in the difference between a finite ΔT with an assumption of C_V independent of temperature, and an infinitesimal δT without that assumption. But more important is that different varieties of latent heat are being considered.

I now think the logical thing to do would be to put in two practically oriented sections on constant volume and constant pressure calorimetry. They would focus on heat of reaction, relevant to Hess's law. They would be separate from the present theoretical sections, which are focused on latent heats with respect to mechanical factors. Delete my present theoretical sub-section on infinitesimal constant volume bomb calorimetry, restoring instead the pre-existing section on practical bomb calorimetry, though clarifying the focus on heat of reaction. I don't know exactly how to create the new practical section on constant-pressure calorimetry, focused on heat of reaction. A little task. I have had something like this in the very back of my mind for a long time, but now it seems something should be done!Chjoaygame (talk) 22:24, 1 November 2015 (UTC)

The new section on Practical constant-volume calorimetry looks good except for the final sentence: Since in constant-volume calorimetry the pressure is not kept constant, the heat measured does not represent the enthalpy change. As you pointed out above for the Hess's law article, what is important is the net change rather than the path. So here we need something such as: Since in constant-volume calorimetry there may be a net pressure change (or else the initial and final pressures may not be equal), the heat measured may not represent the enthalpy change. Or we could just include the explicit equation ΔH = ΔU + Δ(PV) ≅ ΔU + RT Δn_gas. Dirac66 (talk) 23:14, 1 November 2015 (UTC)

Thank you for this. I had just copy-and-pasted the pre-existing section back into the present article. I have now followed your suggestion, but not exactly. Also I have now adjusted the wording. Perhaps you will check it again?Chjoaygame (talk) 01:19, 2 November 2015 (UTC)

Still no action on the heat-of-reaction task!Chjoaygame (talk) 01:27, 2 November 2015 (UTC)

heat of reaction

I think the new section of the present article is OK now. I am not sure what you mean by the heat-or-reaction task. If you mean the Hess's law article which we were discussing above, I have just added a sentence linking it to the present article, so that readers of Hess's law can find the experimental details here. Dirac66 (talk) 02:00, 2 November 2015 (UTC)

I mean that a heat of reaction is a special kind of latent heat. It isn't conjugate with an ordinary heat capacity. An ordinary heat capacity tells you how much heat is needed to change the temperature without such special effects as phase change or chemical reaction, and without a specified kind of mechanical change, such as for example, without pressure change. The present article on classical calorimetric theory, pre-thermodynamic, talks about the latent heats that are, you might say, conjugate with such ordinary heat capacities. For example, one could, at constant temperature, find the infinitesimal heat transfer needed for an infinitesimal volume change at near enough a specified pressure. Heats of reaction are not described by such mechanical latent heats. This present calorimetry article says nothing about heats of reaction and so is useless for those interested in Hess's law. This is a grave defect, and its remedy a significant task. At least, I think so.Chjoaygame (talk) 02:44, 2 November 2015 (UTC)

Hess's law is about heats of reaction. They are latent heats. That is why the Hess's law heats must have fixed common end-point temperatures: to make them latent. They can have either common end-point volumes (internal energy formulation) or common end-point pressures (enthalpy formulation), at the experimenter's pleasure or convenience.Chjoaygame (talk) 03:25, 2 November 2015 (UTC)

There is more about the measurement of heats of reaction in the complementary articles Calorimeter and Reaction calorimeter. These two articles are more focussed on devices. Dirac66 (talk) 11:53, 2 November 2015 (UTC)

pronunciation guide

I don't Wikipedia's guidelines for which pages can get pronunciation guides is, but if this one applies, it should probably get one. When I was researching this topic, I first thought it was pronounced /kəˈlor.ɪ.mɛt.ri/, and asked some other people, who had not heard the term before. I looked to the wikipedia page, but it had nothing, so I had to use something like howtopronounce.com, but those kinds of sources never have IPA for whatever reason. I eventually found out that the correct pronunciation is something like /kæ.ləˈrɪm.ə.tri/ . It would be helpful if this was in the beginning of the article.

Richmann's law

A few month ago, i created the article Richmann's law, which was the first equation for calorimetric calculations and should therefore be mentioned here. My english is to bad, to write in a proper scientific language. Maybe someone else can implement it and double check the new article. Thank you and greetings from german wikipedia. LukeTriton (talk) 06:13, 31 January 2023 (UTC)