[FRIAM] Entropy Redux

[Nicholas Thompson]

Thanks everybody.   Anybody else?   Remember, please no peeking.  Your
efforts have already helped me identify an ambiguity in how I stated the
problem.  Here is an edited version.  See if that clarification changes any
answers.
Remember, no peeking before you kick in your answers.  No herding allowed.

Side by side, butt-to-butt, two cylinders of air, of equal volume and equal
temperature, but different histories. They are separated by a frictionless
sliding divider which is now pegged.  Before compression or heating, both
started with air at 10 degrees C, and after compression or heating, both
arrive at 20 degrees C. The left one has arrived at its present temperature
and volume by being compressed, the right-hand one by having its volume set
to the same value as the left, BEFORE BEING FILLED WITH AIR AT 20 DEGREES
C, and ONLY  then having contents  heated.  All compartments insulated, all
manipulations quasi-static.  Now, remove the peg, allowing the partition
between the two parts to slide, one way or the other.  Which way would it
slide and why. What would your explanation be?  Please don't read others'
answers until you have submitted your own.  This is enormously helpful to
me.

On Tue, May 27, 2025 at 10:19 PM Pieter Steenekamp <
pieters at randcontrols.co.za> wrote:

> Assuming the pressures were equal at the start, it will slide from the
> left (having been compressed) to the right.
> From the ideal gas law PV = nRT, both have equal nRT;s so the one with
> smaller V must have higher P and it would then push to the right.
>
> On Wed, 28 May 2025 at 04:59, Nicholas Thompson <thompnickson2 at gmail.com>
> wrote:
>
>> Side by side, butt-to-butt, two cylinders of air, of equal volume and
>> equal temperature, but different histories. They are separated by a
>> frictionless sliding divider which is now pegged.  Before compression or
>> heating, both started with air at 10 degrees C, and after compression or
>> heating, both arrive at 20 degrees C. The left one has arrived at its
>> present temperature and volume by being compressed, the right-hand one
>> by having its volume set to the same value as the left and then having
>> contents  heated.  All compartments insulated, all manipulations
>> quasi-static.  Now, remove the peg, allowing the partition between the two
>> parts to slide, one way or the other.  Which way would it slide and why.
>> What would your explanation be?  Please don't read others' answers until
>> you have submitted your own.
>> --
>> Nicholas S. Thompson
>> Emeritus Professor of Psychology and Ethology
>> Clark University
>> nthompson at clarku.edu
>> https://wordpress.clarku.edu/nthompson
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-- 
Nicholas S. Thompson
Emeritus Professor of Psychology and Ethology
Clark University
nthompson at clarku.edu
https://wordpress.clarku.edu/nthompson
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