Re: Entropy and states of matter

[John Mallinckrodt <ajmallinckro@CSUPOMONA.EDU>]

On Tue, 26 Feb 2002, Malot, Woody wrote:

> I have done what John suggests for many years.  This years
> class does not want to accept this.  They feel that the
> increase in the universe is due to other causes.

This sounds very odd to me.  You seem to be suggesting here that
your students DO accept the validity of the second law in the case
of condensation, but that they prefer to assign the explanation to
causes other than the obvious heat evolved in the process.  What
DO they offer as examples of these "other causes"?

> I have taught the physics here for 12 years and this is the
> most difficult group to banish preconcieved ideas that I have
> had.

I don't think you can blame improper conceptions about entropy on
preconceived ideas.  Few students bring preconceptions about
entropy to our classes.  On the other hand, I wonder if there
isn't a hint in all of this that your students are actually
balking at the concept of identifying entropy as a measure of
"disorder." The pitfalls of using this approach have been well
documented.  If your students have been taught that entropy is a
measure of disorder, they are unlikely to see any
"overcompensating increase in disorder" accompanying condensation.
However, if you take the time to make the proper connections
between entropy, internal energy, and heat, things ought to go
more smoothly.

John Mallinckrodt      mailto:ajm@csupomona.edu
Cal Poly Pomona          http://www.csupomona.edu/~ajm