Rigorous and General Defnition of Thermodynamic Entropy. Part I: Basic Concepts and Energy

A rigorous and general defnition of entropy is proposed, which is based on operative defnitions of all the concepts employed and involves neither the concept of heat nor that of quasistatic process; it applies to both equilibrium and nonequilibrium states and considers also systems with movable internal walls and/or semipermeable walls, with chemical reactions and/or external force fields, with small numbers of particles. In Part I, the defnitions of the basic concepts and of energy are presented