To consider energy, we need to understand the meanings of some fundamental concepts such as energy, work, and heat. We begin with these essential ideas and energy units. The first law of thermodynamics is a generalization that describes some of the constraints governing the generation and use of energy. This law links energy, work, and heat. With this foundation we turn to a consideration of energy sources and uses in the past, the present, and the future. Insight into the sources of energy requires a look at what happens at the molecular level when a chemical reaction occurs. We describe these energetic transformations in qualitative terms and then use bond energies to calculate the energy changes associated with typical combustion reactions. Most of the energy currently used in home and industry comes from fossil fuels, so the topics of coal and petroleum are explored in some depth and detail. But the supplies of these fuels are limited, so the text then turns to discuss substitutes and additives from various sources, including renewable biological sources such as corn.

Mechanisms for transforming energy come under scrutiny next. Such mechanisms are subject to the second law of thermodynamics, another natural constraint. We introduce the second law to explain the inescapable inefficiencies of energy transformation. Along the way we develop the concept of entropy, a measure of disorder and an indication of the directionality of natural change. The chapter concludes with some observations on the importance of conserving energy and fuels.