Re: [Phys-L] phase change

["Daniel V. Schroeder" <dschroeder@weber.edu>]

Carl Mungan asked:

> 1. Do the particles in the gas and in the solid have the same (a) average kinetic energy?

Classically, yes, by the equipartition theorem.  Quantum mechanically, no, unless you're reasonably close to the high-T limit where the equipartition theorem applies.  At lower temperatures there's an exponential suppression of vibrational modes with hf >~ kT.

> (b) average total energy?


Absolutely not.  The average potential energy per particle in the solid is negative, compared to the gas.

Carl, I still get the impression that you're looking for a purely mechanical (rather than thermodynamic, or statistical, or kinetic) explanation here.  Is that a fair statement?

Dan