What You Always Wanted to Know about Heat Capacities, but Were Afraid to Ask

This review focuses on heat capacities of chemically non-reacting liquids, vapors/gases and mixtures/solutions of nonelectrolytes. Following the leitmotif outlined in the title, after a brief general introduction the most important basic thermodynamic relations and definitions will be summarized, the emphasis being, of course, on those of direct relevance for heat capacities. Then, in the following section, a few selected topics involving heat capacities (and related quantities) will be discussed in some detail, the emphasis being on establishing exact relations linking important thermodynamic properties to experimentally (easily) accessible quantities. Here, "importance" relates to different areas of thermophysics, ranging from the elucidation of the fundamental pair-potential-energy function via second virial coefficients to global fitting excess molar quantities, i.e. from basic problems to problems encountered in chemical engineering. Altogether, the material presented should contribute decisively towards an improved description of real macroscopic systems.