This course describes the fundamental competition between energy and disorder that determines the state of materials at equilibrium. It introduces the laws of thermodynamics, the concept of equilibrium, and thermodynamic potentials. Both classical and statistical interpretations of entropy are presented, but the emphasis of the course is on classical thermodynamics. Topics covered include unary systems, reacting chemical systems, and binary phase diagrams. Emphasis is placed on the concept of constrained equilibrium, the mathematical structure of classical thermodynamics, and on free energy-composition diagrams that underpin binary phase diagrams. Computational thermodynamics is also covered, and thermodynamics software is used throughout the course. The course also emphasizes the uses of thermodynamics is materials selection and process design, and the importance of materials data.