ABSTRACT
Recall that energy cannot be extracted from a system that is constrained unless the thermodynamic constraint is removed. Fossil fuels such as coal, oil, and natural gas are stored below the earth’s surface and are in thermal, mechanical, and chemical equilibrium. If the fuels are allowed physical contact with air i.e. if the chemical constraint is removed, it is possible to release chemical energy. Œe direction of heat flow is determined by a temperature gradient or potential, that of fluid flow by a pressure gradient or a mechanical potential. We will learn in this chapter that the gradient of the Gibbs energy or chemical potential determines the direction in which a chemical reaction proceeds.
