ABSTRACT
This chapter provides both analytical and an intuitive understanding of the second law of thermodynamics for students. The second law is beautiful in its predictive power, but compared to its counterpart in the first law, it can appear to be rather untidy, and mastering its subtleties can be difficult. Students learn the importance of reversibility and irreversibility in the second law, and how the entropy acts as a potential for spontaneous change and for determining stable equilibrium configurations. The use of entropy as a thermodynamic potential for isolated systems will be developed. Spontaneous thermal change is seen when two bodies at different temperatures are connected by a heat-conducting boundary. The Clausius and Kelvin statements give the direction of spontaneous change, either through heat flow or through work done by heat engines. The entropy change for this irreversible adiabatic expansion is compared to reversible expansions.
