Boltzmann’s Equation

Thermodynamics describes the relationship between heat, work, energy and motion. The key concepts are the conservation of energy and the maximisation of entropy (or disorder) as given by the first and second laws of thermodynamics. Boltzmann’s equation explains how the entropy of a material is related to the disorder of its atoms or molecules, as measured by the probability or the number of equivalent atomic or molecular structures. This chapter examines thermodynamic properties such as internal energy, enthalpy and Gibbs and Helmholtz free energy; physical properties such as specific heat and thermal expansion coefficient; and the application of thermodynamics to chemical reactions, solid and liquid solutions, and phase separation. Ludwig Boltzmann’s early life as the son of a minor tax official in Austria is described, as are: his scientific career in a series of Austrian and German universities; his philosophical arguments with Ernst Mach and the phenomenalists about whether atoms do or do not exist; his increasing moodiness, paranoia and bipolar disorder; and his ultimate suicide while trying to recuperate from depression in Trieste.