1. Do Now: We know that our ozone layer is critical for life on earth. However, can it also be harmful if Ozone is found in other atmospheric layers?

2. Aim: How is ozone formed and destroyed?

3. Ozone layer/shield Ozone (O 3 ) absorbs most of the UV radiation from the sun and filters its rays This UV absorbtion causes it to heat up the part of the stratophere that’s closer to the sun (farthest from Earth)

4. Ozone’s effects Tropospheric O 3 = BAD –Causes lung damage because we breathe it in –Greenhouse gas so it traps heat near Earth’s surface Stratospheric O 3 = GOOD –Shields us from UV rays Earth’s sunscreen :)

5. Ozone Depletion Thinning of the stratospheric ozone shield Mostly occurring over South Pole What problems can result because of this?

6. Destruction of ozone Chlorofluorocarbons (CFCs) react to destroy ozone UV rays easily break the bond between the Cl-FC Free chlorine attacks Ozone in the reaction O 3 +Cl --> O 2 + (Cl+O) The bond between Cl – O is unstable so it is easily broken leaving the Cl to attack another ozone molecule

7. Pic: CFC destroying Ozone

8. CFCs developed in the early 1930s desirable safety characteristics –non-toxic, non-flammable, and non-reactive with other chemical compounds. stable thermodynamic properties used in a variety of industrial, commercial, and household applications. –coolants for commercial and home refrigeration units, aerosol propellants, electronic cleaning solvents, and blowing agents.

9. Greenhouse Gas Build up #1 Carbon Dioxide (CO 2 ) –Fossil fuel use –Deforestation #2 Methane (CH 4 ) –Microbial fermentation at landfills –Coal & oil deposits –Natural gas pipelines –Cows waste (manure)

10. Greenhouse Gas Build up cont’d… #3 Nitrous Oxides (NO x ) –Biomass burning –Chemical fertilizers –Fossil fuels burning

11. Chart: Greenhouse vs Ozone Shield Greenhouse Effect Ozone Shield Where? TroposphereStratosphere What happens? Traps heat near Earth’s surface Filters UV radiation Benefits Keeps Earth warm enough for life to exist Protects us from sun’s harmful rays forming cancer & from overheating Which gases? Water vapor, carbon dioxide, methane Oxygen gas, Ozone Problem Global warmingOzone depletion If problem persists Annual increase in temp. leads to ecosystem destructions More UV radiation exposure resulting in more cancer

12. Pic: Too many greenhouse gases