Talk:Table of thermodynamic equations

This page was created as a result of a discussion in Talk:Thermodynamic_equations following major edits to that page. It was generally agreed to take the earlier table-of-equations content, starting with the last revision before the major change and move it to a new page named Table of Thermodynamic Equations. --Pmetzger 16:54, 19 December 2006 (UTC)

Agreed. Hard Raspy Sci 04:44, 3 January 2007 (UTC)

Given that everything on the page is expressed in extensive quantities, why are the lower case 'w' and 'q' used for work and heat, respectively? If there is some rational for this choice, the definition for entropy is inconsistent. Otherwise, capital letters seem more appropriate and should be instituted throughout. Thermodude 23:00, 10 July 2007 (UTC)

Please review the change for sign from S=dF/dT to S=-dF/dT in "General derived quantities" table
I have changed the sign in the equation for entropy. It comes from the fundamental thermodynamic relation: dF(T,V)=-SdT-PdV and dG(T,P)=-SdT+VdP. — Preceding unsigned comment added by 131.180.28.89 (talk) 11:31, 2 November 2017 (UTC)

Sign correct?
In the equation table for an ideal gas, shouldn't internal energy at a constant pressure be q - PΔV instead of q + PΔV (since U = q + w and w = -PΔV)? 199.8.26.10 14:43, 26 September 2008
 * By convention, work done by the system is +W, therefore dU=dQ-dW. From the definition of mechanical work follows that dW=pdV, i.e. dU=dQ-PdV.  I think that table should be scrutinized Power.corrupts (talk) 10:20, 5 October 2008 (UTC)


 * I think the problem we have here is that chemists use one sign convention, while physicists use another.--199.8.26.10 (talk) 20:48, 19 October 2008 (UTC)


 * There is no internal consistency in the article then. The First law of thermodynamics is presented as $$~ dU=\delta q-\delta w ~$$ - clearly +w is work done by the system. Power.corrupts (talk) 21:55, 19 October 2008 (UTC)


 * Okay, I made a few adjustments to try to fix the problem of internal consistency. Feel free to revert if you wish. My edits use $$+w$$ to denote work done on the system. --199.8.26.10 (talk) 11:15, 20 October 2008 (UTC)


 * That's fine, Wiki encourages you to be bold. The sign convention you suggest is contrary to the one in Perry's Chemical Engineers' Handbook, hence I fact marked it. It's also contrary to the convention in Thermodynamic equations.  Sign conventions are pretty basic stuff and discrepancies at this fundamental level, and some other issues with the table, make me feel at unease with the whole article, hence I tagged it as disputed. I have not been exposed to thermodynamics for years (not to say decades), I dont even have my old textbooks with me, so I wont be bold.  The best thing that could happen to this article is if a good student revised the entire article, with proper inline citations. Power.corrupts (talk) 14:32, 20 October 2008 (UTC)


 * Recent lower division college level physics courses that I have taken have been using the convention that anything leaving the system is negative, and anything entering the system is positive. So work done by the system to its surroundings would result in a negative value for work, and heat added to the system would be a positive value and so on. I think this is the approach chemists use. It think that originally work had been switched in physics because it is more intuitive to think of work as being a positive value, or something that was done by the system and not to the system.--68.8.229.229 (talk) 07:44, 2 February 2009 (UTC)

Equation Table for an Ideal Gas
The table says the general entropy equation is : $$\begin{matrix}\Delta S=-\int_{T_1}^{T_2} \frac {C}{T}dT \end{matrix}$$ I find this suspicius, as for an ideal gas, the general equation for entropyp is dS=(Cp/T)dT - (R/P)dP. What happened to the last part of this equation? and how can the index on heat capacity C disappear, in my opinion it is not defined at all, without the index? Also, could somebody with a more recent knowledge than I on this subject review the ideal gas page, which has sidetracked into a lot of thermodynamics. Power.corrupts (talk) 13:26, 30 September 2008 (UTC)
 * I have fact marked the two equations Power.corrupts (talk) 10:20, 5 October 2008 (UTC)


 * There is an equation in the quantum properties section that states N*$$S...$$ I think someone ought to actually to the math first and post a real solution. —Preceding unsigned comment added by 137.99.20.179 (talk) 18:15, 15 October 2009 (UTC)

Sign convention
The majority of texts use a sign convention of heat into the system is positive Q and work done by the system on its environment is positive W. I have changed equations to this convention. Examples of texts that follow this include Moran & Shapiro, Keenan, Cengel & Boles, Halliday & Resnick. An example of a book using the other convention for Work is Zemansky & Dittman. This sign convention makes sense in the context of a heat engine a la Carnot, where positive work is generated using positive heat, and is universal in the field of engineering, in my experience. Jdpipe (talk) 01:18, 5 February 2009 (UTC)

Paring down this page
This page is a random collection of equations from all over the place. I would like to pare this page down, organize it as a set of links to other pages and not repeat the equations here. As the main pages evolve, their statements of the equations change, but this page is not updated. It should not have to be. I have eliminated a few equations, leaving only their links to main articles. If this is ok, then we can continue the process until this page is just a collection of organized links.

Errata in the work formula for an ideal gas in a reversible adiabatic process
It should be $$P_{i}$$ and $$V_{i}^{\gamma}$$ instead of $$P$$ and $$V^{\gamma}$$ in $$\frac{P V^{\gamma}\left(V_{f}^{1-\gamma}-V_{i}^{1-\gamma}\right)}{1-\gamma}=C_{V}\left(T_{2}-T_{1}\right)$$. Indeed, $$\frac{P_{f} V_{f}-P_{i} V_{i}}{1-\gamma}$$ is simpler. Quaerendo I (talk) 09:32, 27 May 2021 (UTC)