The main goal of this book is to logically and rigorously explain thermo-dynamics from first principles, clearly elucidating the concepts derived in thermodynamics and those primitive to it. The text covers classical thermodynamics and conveys to the student the logic and simplicity of the subject matter through the axiomatic method consisting of the following four steps: • Concepts and methods adopted from other disciplines (the primitives of thermodynamics) are indicated clearly. • The terminology of thermodynamics is developed using the operational definitions of physical quantities. • The laws (axioms) of thermodynamics are stated using this terminology. • The consequences of these laws (theorems) are derived and proved.