Chapter 7

Energy and Chemical Reactions

249

nergy…it makes things happen. To get an idea of the role energy plays in our lives, let’s spend some time with John, a college student in one of the coastal towns in California. He wakes up in the morning to a beautiful sunny day and decides to take his chemistry book to the beach. Before leaving, he fries up some scrambled eggs, burns some toast, and pops a cup of day-old coffee in the microwave oven. After finishing his breakfast, he shoves his chemistry textbook into his backpack and jumps on his bike for the short ride to the seashore. Once at the beach, he reads two pages of his chemistry assignment, and despite the fascinating topic, gets drowsy and drops off to sleep. When he wakes up an hour later, he’s real sorry that he forgot to put on his sunscreen. His painful sunburn drives him off the beach and back to his apartment to spend the rest of the day inside.

All of John’s actions required energy. It took energy to get out of bed, make breakfast, pedal to the beach, and (as you well know) read his chemistry book. John gets that energy from the chemical changes that his body induces in the food he eats. It took heat energy to cook his eggs and burn his toast. The radiant energy from microwaves raised the temperature of his coffee, and the radiant energy from the sun caused his sunburn.

What is energy, and what different forms does it take? Why do some chemical changes release energy while others absorb it? This chapter attempts to answer such questions and then apply our understanding of energy to some of the important environmental issues that people face today.

7.1 Energy

7.2 Chemical Changes and Energy

7.3 Ozone: Pollutant and Protector

7.4 Chlorofluorocarbons: A Chemical Success Story Gone Wrong

Review Skills

The presentation of information in this chapter assumes that you can already perform the tasks listed below. You can test your readiness to proceed by answering the Review Questions at the end of the chapter. This might also be a good time to read the Chapter Objectives, which precede the Review Questions.

Describe the similarities and differences between solids, liquids, and gases with reference to the particle nature of matter, the degree of motion of the particles, and the degree of attraction between the particles. (Section 2.1)

Describe the relationship between temperature and motion. (Section 2.1)

Radiant energy from the sun causes sunburn

Photo by Dean Tersigni