CHAPTER 3 – State- and Path-Dependent Properties

This chapter discusses the state- and path-dependent properties of a system. A system approaching thermodynamic equilibrium in infinitesimally slow steps is characterized by reversibility of the steps without a change in the energy status of the infinitesimal transitions. At equilibrium, the integral of the variables is constant, so that a change in one limits change in the others. The integral is a state function, and the associated properties are state properties. If an integral of identical variables depends on the pathway, the properties are path-dependent and inexact, The examples of inexact properties are sorption, hysteresis, etc. The thermodynamics of small molecules is predicted on equilibrium states arrived at in relatively short time intervals, making them essentially time-dependent. Polysaccharide processes seldom reach thermodynamic equilibrium in a practicable time interval. A pair of polysaccharide molecules approaching each other in water exerts an interaction potential (ξ’) that is the algebraic sum of the competing attractive and repulsive forces.