版权所有：华东理工大学物理化学教研室 3 This chapter will explain the origin of the spontaneity of physical and chemical change. Two simple processes are examined. It shows that a property, the entropy can be defined, measured, and used to discuss spontaneous changes quantitatively. This chapter also introduces a major subsidiary thermodynamic property, the Gibbs energy. 4. The Second Law: the concepts版权所有：华东理工大学物理化学教研室 3 This chapter will explain the origin of the spontaneity of physical and chemical change. Two simple processes are examined. It shows that a property, the entropy can be defined, measured, and used to discuss spontaneous changes quantitatively. This chapter also introduces a major subsidiary thermodynamic property, the Gibbs energy. 4. The Second Law: the concepts