Thermodynamics, which comes from the Greek word meaning "heat motion" is the science that studies the transfer of energy among different bodies. When a typical power plant produces electricity, water is heated to produce steam by burning fuel. The steam is allowed to expand and perform work, which turns an electric generator that produces electrical energy. The efficiency of this process of energy production—how much electrical energy can be produced for burning a given amount of fuel—is determined by the laws of thermodynamics. These same laws are equally important for the heat engines that propel millions of planes, trains and automobiles around the world. In fact, nearly all energy that powers our energy intensive economy involves, in some manner, the laws of thermodynamics.

Scientific descriptions of nature can be categorized as microscopic or macroscopic. A microscopic description involves a discussion of the system using...