ABSTRACT
Work, heat, internal energy, and temperature are all concepts that appear in, and are central to, thermodynamics. This chapter presents a simple graphical summary showing that energy can be transferred to or from a system, changing the system's stored energy. In the development of thermodynamics, it became clear that the powerful principle of conservation of energy was not enough to explain physical behaviour of macroscopic systems. For example, energy conservation does not explain why a cup of hot coffee cools down to approximately room temperature, but a cup of room temperature coffee does not heat up spontaneously. The concept of equity is inspired by the realisation that the energy spreading phenomenon cannot be explained solely using conservation of energy. Energy tends to spread only in certain ways, namely, ways that lead to increased equity. While energy and entropy are the hallmark functions of thermodynamics, temperature has a different status. It arises in various ways.
