Although thermodynamics was introduced with the interconnection of work and heat, its range has now greatly increased. Heat is generated or absorbed by any chemical reaction, so thermodynamics is also an essential part of chemistry. The second law of thermodynamics also gives the direction of spontaneity, so that it is known whether a chemical reaction will proceed spontaneously or under what conditions. Thermodynamics is also at the core of battery strategy. Again the whole organism is dependent on spontaneous chemical reactions like photosynthesis. These are the topics discussed in this book.