Entropy Pollution of the Environment: A Teaching Approach to the Second Law

Abstract

To introduce the concept of entropy to students, we propose building on what is currently a well aired concept, that of thermal pollution of the environment. This is then clarified, refined and made quantitative by the addition of the quality of heat, the temperature. The student will be familiar with the idea that temperature differences drive heat flows. The new concept is that the individual temperatures are significant, not just their difference. A high temperature drives a heat flow to a low temperature and in so doing can provide something useful, like work. We pollute our environment if we dissipate this opportunity. This approach leads naturally to the Second Law, to Carnot efficiency and the Kelvin scale.