1 Introduction
Section 1.1 looks at the similarities and differences between classical thermodynamics and statistical thermodynamics. Then, in Section 1.2, we see several examples of phenomena that are beautifully described by statistical mechanics. Section 1.3 lists practices of notation adopted by this book.
1.1 Classical Thermodynamics and Statistical Thermodynamics
Classical thermodynamics, when applied to a closed system, starts with two fundamental laws. The first law of thermodynamics accounts for a balance of energy:
where the system receives heat d′Q and work d′W to change its internal energy by dU (see Figure 1.1). The prime in “d′” indicates that the quantity may not be a thermodynamic variable, i.e. not expressed as a total derivative. When the volume of the system changes from V to V + dV, d′W = −p dV, where p is the pressure.
Figure 1.1 A closed system received heat d′Q and work d′W from the surroundings to change its internal energy by dU.
The second law of thermodynamics expresses d′Q by a thermodynamic variable, but only when the change is reversible:
where T is the temperature. The second law introduces the entropy S.
In classical thermodynamics, ...