This monograph develops a unified microscopic basis for phases and phase changes of bulk matter and small systems, in terms of classical physics. It describes the thermodynamics of ensembles of particles and explains phase transition in gaseous and liquid systems. The origins of such phase changes are derived from simple but physically relevant models of how transitions occur between rigid and fluid states, of how phase equilibria arise, and how they differ for small and large systems.

R. Stephen Berry is James Franck Distinguished Service Professor Emeritus in the Chemistry Department at The University of Chicago. He has studied phase changes and phase equilibria for twenty years. He is a MacArthur Fellow and a Member of the National Academy of Sciences of the U.S.A., and has been author or coauthor of five books prior to this. He and his coauthor of this book have known each other for over 40 years, from the time both were working on atomic collision processes. They have been collaborating for about 10 years, in their studies of clusters and of phase transitions.

Boris M. Smirnov is a distinguished physicist who worked for many years at the Institute for Ball Lightning, prior to his joining the Institute for High Temperatures in Moscow.