This course focuses on the basic principles governing the equilibrium behaviour of macroscopic systems, and applications to systems of interest in modern chemical engineering. After a brief review of material covered in Thermodynamics 2, we begin by introducing fundamental concepts: thermodynamic potentials; criteria of equilibrium and stability; and introduction to the molecular basis of thermodynamics. These concepts are then applied to the analysis and solution of problems such as calculating the equilibrium composition of coexisting phases and reacting mixtures.