Solving problems-a chemistry handbook

A chemical is any substance that has a definite composition. Ozone is a chemical that is made up of three particles of oxygen. Ozone forms a thick blanket above the clouds in the stratosphere. This layer of ozone protects Earth from overexposure to ultraviolet radiation from the Sun. You are probably familiar with the damage that exposure to ultraviolet radiation can do to your skin in the form of sunburn. Ultraviolet radiation can also harm other animals and plants. In the 1980s, scientists documented that the ozone layer around Earth was becoming measurably thinner in some spots. In the 1970s, scientists had observed that large quantities of chlorofluorocarbons (CFCs) had accumulated in Earth’s atmosphere. CFCs are chemicals that contain chlorine, fluorine, and carbon. CFCs were used as coolants in refrigerators and air conditioners and as propellants in spray cans because they were considered relatively nonreactive. Some scientists hypothesized that there might be a connection between the concentration of CFCs in the atmosphere and the thinning of the ozone layer.