Chapter 12 - Thermodynamics of Other Variables

Abstract

This chapter introduces additional variables other than pressure, velocity, temperature, internal energy, entropy, enthalpy, Helmholtz free energy, and Gibbs free energy to tie thermodynamic equations to other types of processes. For example, the stretching of a rubber band if a rubber band is taken and a stress is introduced by hanging a weight on it, and then hot air is blown on the rubber band, it is discovered that with the constant force, the rubber band contracts with heating. Thermodynamics can be used to understand this effect. Stretching the rubber lines up the strands of polymer that increases the order and decreases the entropy. This decrease in entropy releases heat that increases the temperature of the rubber until the heat is removed. When two phases, such as (solid + liquid), (liquid + gas), and (solid + gas) are brought together, a boundary known as a surface or interface is present. The chapter uses thermodynamic relationships to describe only the bulk properties of a substance and considers the surface properties to be negligible. It also discusses the effects of curvature on the properties of pure substance surfaces and derives relationships to obtain the difference in the thermodynamic properties of a flat surface or the bulk phase, and small droplets.