Thermodynamics is the science dealing with energy and its transformation. The laws of thermodynamics are of wide applicability and are extensively used in several branches of engineering science. In the study of thermodynamics, one can adopt two different points of view, namely microscopic and macroscopic. Since the purpose of this book is to serve as an introduction to the study of thermodynamics, the macroscopic approach has been adopted. It presents the essential concepts and principles, with particular emphasis on precise and logical presentation.