This new edition of Robert G. Mortimer's Physical Chemistry has been thoroughly revised for use in a full year course in modern physical chemistry. In this edition, Mortimer has included recent developments in the theories of chemical reaction kinetics and molecular quantum mechanics, as well as in the experimental study of extremely rapid chemical reactions. While Mortimer has made substantial improvements in the selection and updating of topics, he has retained the clarity of presentation, the integration of description and theory, and the level of rigor that made the first edition so successful.