# Chapter 2: Concepts and Processes

This chapter discusses how we can relate different properties of materials to each other and how these properties change under certain kinds of processes. The discussion is based on the first and second laws of thermodynamics. The first law is a statement of conservation of energy with energy changes divided into two types: work and heating or cooling. The second law states that the we need a new quantity, entropy, such that for an isolated system the entropy never decreases no matter what happens inside the system. When the system comes to equilibrium, the entropy stops changing. From this idea we can predict why energy goes from a hotter object to a cooler object.

There are no problems in this chapter that use numerical techniques or simulations, because the strength of thermodynamics is its ability to relate properties of materials without knowing the microscopic laws underlying the macroscopic behavior of those materials. A concise stand alone introduction to thermodynamic thinking is given in Chapter 2 of *Statistical and Thermal Physics: With Computer Applications*, 2nd ed., Harvey Gould and Jan Tobochnik, Princeton University Press (2021).