Second Law of Thermodynamics, Gibbs’ Thermodynamics, and Relaxation Times of Thermodynamic Parameters

The relationship between the second law of thermodynamics and Gibbs’ thermodynamics is discussed. The second law of thermodynamics is formulated more generally than Gibbs’ thermodynamics, which considers only strictly equilibrium values of thermodynamic functions. Gibbs’ approach generalizes the statistical mechanical theory of equilibrium for thermodynamic variables, except for the difference between the periods of relaxation of all thermodynamic parameters. For small systems, this approach consists of replacing the real physical nature of systems with the stratification of coexisting phases using a model with an interface of mobile phases in contact with a foreign (nonequilibrium) body. For solids, this results in confusion of concepts of the complete phase equilibrium of a system and the mechanical equilibrium of a deformed solid. These two problems are revealed using the molecular kinetic theory of condensed phases, ensuring a self-consistent description of three aggregate states and their interfaces. This theory allows the concepts of the times of the onset and completion of forming entropy in the considered system to be introduced. Allowing for experimental data on the ratios between the measured periods of relaxation for momentum, energy, and mass transfer processes in considering real processes not only ensures a solution to the two problems noted above; it also testifies to the redundancy of the Carathéodory mathematical theory to substantiate the introduction of entropy into multicomponent mixtures. A microscopic interpretation of the formation of entropy in closed systems is given that illustrates the essence of processes preceding the emergence of the reaction completeness parameter in de Donder and Prigogine approaches. Systems in which allowing for periods of relaxation alters existing theories are discussed.