The Transition from Microscopic to Macroscopic: Statistical Thermodynamics

Abstract

5As indicated in Chapter 1 , in liquids a natural reference state is absent because the structure is highly irregular. Therefore, in the description of liquids and solutions, we essentially will need statistical thermodynamics, which provides the link between the microscopic considerations and concepts to the macroscopic -in particular thermodynamic -aspects. In this chapter we introduce and outline statistical thermodynamics in a concise way. First, we deal with the basic formalism and apply that to noninteracting molecules. Thereafter, the effect of intermolecular interactions is introduced, leading to the virial description. While being a reasonable approach for low-and medium-density fl uids, the virial approach does not work for liquids. The reasons for this are briefl y discussed. Statistical Thermodynamics ⎞ ⎠ ⎟ +…At high temperature the summation can be approximated by integration and thus