ABSTRACT
This chapter focuses on ‘thermodynamics’, probably the most important model in science. Central to the thermodynamic model is ‘energy’, and although we can define energy broadly as the capacity to do work, it is a very elusive concept. The ‘energy well’ model provides a useful introduction to energy and to thermodynamics. Engineers originally developed the thermodynamic model to help them improve the efficiency of steam engines. An important idea built into the thermodynamic model is that of ‘reversibility’, a word with a much more precise meaning in thermodynamics than in everyday use. The thermodynamic model involves the definition of entropy as the quantity of heat divided by the temperature, so the lower the temperature the less useful the heat and the greater the entropy. For the community as a whole the total tax paid is greater than the total refunds: tax revenue is always positive. The same is true of entropy.
