Heat and Thermodynamics

12.15 Specific Heats of Substances

The simplest law of specific heat of monatomic solids was given by Dulong and Petit. It runs as follows:

The product of atomic weight and specific heat is the same for all elementary monatomic solid substances and is called atomic heat.

Regnault's experiments on a large number of substances give a mean value of 6.38 calories per gram per degree for specific heats of the substances investigated.

This law can be readily explained on the basis of equipartition principle. An atom of a monatomic solid has three degrees of freedom of vibrational motion; with each degree of kinetic energy, an amount of energy 1/2 kT is associated. Since the average energy of vibrational motion is equally divided between the kinetic ...