Concepts of thermodynamics Equilibrium, energy, and irreversibility
This chapter introduces the concepts of thermodynamics, its basic vocabulary, and the first law of thermodynamics—conservation of energy. It presents the foundations of thermodynamics organized around three concepts: equilibrium, internal energy, and irreversibility. If there wasn't something called entropy out there, the chapter discusses the needs to know about thermodynamics. The type of path independence is ensured mathematically by requiring differentials of state variables to be exact differentials. Internal energy is analogous to, but not the same as mechanical energy. The van der Waals equation of state is a reasonably successful model of the thermodynamic properties of gases. An important concept is that of constraints. A constraint is the restriction of a state variable to certain values. The language of thermodynamics is couched in the measurable properties of macroscopic systems. A definition of macroscopic is elusive, as well as its correlative microscopic.