1. Chapter 1: Introduction to Chemistry Section 1.1 –The Stories of Two Chemicals

2. The Ozone Layer The ozone layer allows living things to exist on Earth It absorbs harmful UV light

3. Earth’s Atmosphere

4. Ozone Formation Ozone = O 3 Located in the stratosphere Formed when oxygen gas is exposed to ultraviolet radiation Oxygen gas  Oxygen particles –Oxygen particles + Oxygen gas  Ozone

5. Ozone Formation Formed in upper stratosphere Stored in the lower stratosphere

6. G.M.B. Dobson Began measuring ozone in the 1920s Normal = 300 DU 1981: ozone recorded at 160 DU over Antarctica

7. What is the DU? The most basic measure used in ozone research. 'Dobson Spectrometer' - measures the intensity of solar UV radiation at four wavelengths, two of which are absorbed by ozone and two of which are not. 1 Dobson Unit (DU) is defined to be 0.01 mm thickness at STP

8. The DU

9. The Ozone is thinning!!

10. The Ozone “Hole” Over Antarctica

11. The Ozone Hole Over Time

12. Chlorofluorocarbons Thomas Midgley synthesized them in 1928 CFC = Cl + F+ C Not naturally occurring Nontoxic, stable Ideal coolant for refrigerators Great propellant for spray cans

13. CFC in the Atmosphere CFC was discovered in the atmosphere in the 1970s Its presences increases every year

14. The Tale of Two Chemicals Ozone CFC