From Microstates to Thermodynamics

As we showed in a previous paper [Chem. Educator2004,9, 74], some of the more subtle aspects of thermodynamics can be understood using Boltzmann’s principle in terms of the number of microstates for an isolated system. We deepen this understanding by explaining microstates of a macroscopic system: what they are, how they can be counted, and how the count can be used to obtain explicit thermodynamic expressions for the system using an ideal monatomic gas as an example in the context of the previous paper. The relation between microstates and thermodynamics is developed further for a chemical reaction. Using elementary methods, we derive exact expressions for the fluctuations of composition in the equilibrium state and discuss the thermodynamic consequences of these.