Re: Adiabatic cooling

[John Cooper <jcooper@BUCKNELL.EDU>]

On Thu, 22 Jul 1999, John Denker wrote:

> > Doesn't ALL mixing (of distinguishable particles) result in COOLING?!?!?!?!
>
> Not "ALL" mixing.  Mixing X with Y results in cooling due to the entropy of
> mixing.  Mixing X with X (e.g. air with air) does not.  It is a simple
> macroscopic demonstration of the reality of quantum identical-particle
> effects.
   In fact, not 'most'.  There's an entropy of mixing, and an enthalpy of
mixing.  Mixing alcohols and water adiabatically results in significant
INCREASES in temperature, owing to specific water-alcohol interactions,
different from water-water or alcohol-alcohol.  Del H of mixing can be
positive or negative; for 'ideal' solutions, in which there are no
differences in interactions between/among the components, Del H = 0.

 John N. Cooper, Chemistry
 Bucknell University
 Lewisburg PA 17837-2005
 jcooper@bucknell.edu
 http://www.facstaff.bucknell.edu/jcooper
 VOX 570-577-3673    FAX 570-577-1739