This chapter introduces some of the basic concepts of thermodynamics. It concentrates
on the conservation of energy—the experimental observation that energy can be neither
created nor destroyed—and shows how the principle of the conservation of energy can be
used to assess the energy changes that accompany physical and chemical processes.
Much of this chapter examines the means by which a system can exchange energy with its
surroundings in terms of the work it may do or have done on it or the heat that it may
produce or absorb. The target concept of the chapter is enthalpy, which is a very useful
bookkeeping property for keeping track of the heat output (or requirements) of physical
processes and chemical reactions at constant pressure. We also begin to unfold some of
the power of thermodynamics by showing how to establish relations between different
properties of a system. We shall see that one very useful aspect of thermodynamics is that
a property can be measured indirectly by measuring others and then combining their values.
The relations we derive also enable us to discuss the liquefaction of gases and to establish
the relation between the heat capacities of a substance under different conditions.