1. 1 Chemistry/Chemistry ACC Blocks 1/2/4 Chapter 1.1 The Story of Two Chemicals Chunk Notes 01/10/11 Dr. Kukla The Death of Socrates, 4 th Century BC

2. 2 The Ozone Layer Chemical: Any substance that has a definite composition (i.e., what it’s made out of). H 2 O = Water 2

3. 3 The Ozone Layer Ultraviolet radiation, given off by the sun, causes sunburns, harms plants, destroys crops, and causes cancer. The ozone layer is a chemical -- O 3 -- in the Earth’s atmosphere that absorbs most of the radiation before it reachers the Earth’s surface. 3

4. 4 The Ozone Layer The Earth’s atmosphere is divided into layers, from lowest to highest: Troposphere (contains the air we breathe) Stratosphere (where 90% of the ozone layer is) Mesosphere Thermosphere Erosphere

5. 5 The Ozone Layer Ozone is formed when ultraviolet radiation breaks oxyegen gas into smaller particles, which then interact with each other to form ozone: O 3

6. 6 The Ozone Layer The Ozone layer was first identified in the late 1800s. Since air currents are found in the stratosphere, the ozone layer was studied as a marker of air flow over the planet.

7. 7 The Ozone Layer In the 1920s, G.M.B. Dobson measured the ozone layer; he measured levels of more than 300 Dobson Units (DU). Most ozone is stored in the lower part of the ozone. It is measured by balloons, satellites, and rockets.

8. 8 The Ozone Layer A group of British scientists began measuring the ozone layer during 1981-1983 over Antarctica in the Spring. In 1985 they determined the ozone layer was thinning.

9. 9 The Ozone Layer The thinning of the ozone is like a worn-out old sock.

10. 10 Chlorofluorocarbons During the 1920s, toxic chemicals were used as coolants in refrigerator and air-conditioning units.

11. 11 Chlorofluorocarbons In 1928, Thomas Midgley Jr. created the first chloroflurocarbons (CFCs), which contain chlorine, fluorine, and carbon.

12. 12 Chlorofluorocarbons They do not occur naturally, are non-toxic, and are stable (i.e., they do not react with other chemicals very easily).

13. 13 Chlorofluorocarbons The US began using them in 1935. They were used as coolants, plastics, styrofoam cups/plates, propellants in aerosol cans.

14. 14 Chlorofluorocarbons During the 1970s, scientists began to notice that the ozone layer was thinning and an increase in CFCs in the atmosphere.