Problem 9-23 in K. Stowe "Intro. to Stat. Mech. and Thermo." boils
down to asking for the number of degrees of freedom per water
molecule (call it n) using equipartition and the specific heat.
I find n = 2*.018*c/8.314 where c is the specific heat at constant
volume in J/kg/K.
Thus I get n = 18 for water using c = 4186. The problem ends there,
but my question is: What does this mean? In what way can a water
molecule be said to have 18?
Interestingly enough, if we try ice (c = 2000) we find n = 8.7 ~ 9 in
accordance perhaps with Dulong-Petit; and if we try water vapor (c =
1520) we find n = 6.6 ~ 6 in accordance with our expectations of 3
translations and 3 rotations (and maybe even a hint of the bending
mode beginning to turn on?).
Texts always seem to discuss solids and gases in connection with
specific heat, but never liquids. Why *does* water have such a high
heat capacity compared to ice or water vapor? Where does it store
away all that extra energy?
--
Dr. Carl E. Mungan, Assistant Professor http://uwf.edu/cmungan/
Dept. of Physics, University of West Florida, Pensacola, FL 32514-5751
office: 850-474-2645 (secretary -2267, FAX -3323) email: cmungan@uwf.edu