I don't disagree with what John Denker has said. But I also think we
have to realize how entrenched classical thermodynamics is/was in
chemistry academia. There are still chemists teaching classical
thermodynamics (delta-S = Q/T). I teach physcial chemistry at Bluffton
College and I did not stop teaching it that way until about 1990. Why,
because we knew that standardized tests such as the GRE were going to
expect chemistry graduates to know the old approach.
The physicists were much quicker to move toward the statistical
thermodynamics approach than the chemists. I had the unpleasant
situation of trying to teach statistical thermodynamics to physics
students and teaching classical thermodynamics to chemistry students.
Finally, about 1990, I merged the two courses into one course and
abandoned the classical approach altogether. For a while this meant I
could not use a physical chemistry text and had to use a thermal physics
text. This made the chemists angry. Recently I have been using the
text Thermal Physics by Daniel Schroeder because he includes more
chemistry than most thermal physics authors.
Also, while Denker is correct that we should define temperature in terms
of entropy, we need to remember that classical thermodynamicist really
did do it the other way. The early guys all "knew" what temperature
was, but did not know statistical thermodynamics. Therefore, when
trying to make sense out of why something happened the way it did, they
eventually came up with this Q/T idea that worked. Once that became
established it might be that the "if it works, don't' fix it" attitude
became pretty strong.
Whatever the reason, the idea that delta-S is Q/T is still way more
prevalent in chemistry than it should be.
Michael D. Edmiston, Ph.D.
Professor of Chemistry and Physics
Bluffton College
Bluffton, OH 45817
(419)-358-3270
edmiston@bluffton.edu