Microscopic Interpretation of Thermodynamics

Abstract

Thermodynamics and statistical mechanics give complementary descriptions of the physical processes, from a macroscopic and microscopic point of view respectively. Matter is made of an enormous number of molecules. Statistical mechanics starts from the laws of mechanics to extract the equations governing the mean values of the molecular kinematical quantities and their statistical distributions. We develop the kinetic model of gases and learn the physical meaning of pressure and internal energy. We experimentally control the predictions of the model and see how classical mechanics reaches its validity limits. We study the molecule kinetic energy and velocity distributions, and the fundamental Boltzmann law. We finally demonstrate the physical reasons of why microscopic phenomena are reversible, macroscopic ones are not and understand the physical meanings of entropy and of the second law of thermodynamics.