The application of thermodynamic principles to systems involving physical and chemical transformations is carried out in order to (1) develop quantitative relationships among the identifiable forms of energy and their conjugate variables, (2) establish the criteria for spontaneous change, for equilibrium, and for thermodynamic stability, and (3) provide the macroscopic base for the statistical-mechanical bridge to atomic and molecular properties. The thermodynamic principles applied are the conservation of energy as embodied in the first law of thermodynamics, the principle of entropy production as embodied in the second law, and the principle of absolute entropy and its statistical thermodynamic formulation as embodied in the third law of thermodynamics.