1. Ozone and the Scientific Method

2. The Scientific Method Observation
State the Problem (worded as a question)
Gather information
Form a Hypothesis (if…then…)
Experiment to test the hypothesis
(the experimental group will have ONE variable that differs from the control group)

3. Independent Variable – being tested
Dependent variable- being measured
6. Record and analyze data (charts, tables, graphs)
7. Draw Conclusions
8. Repeat to check for accuracy
9. Publish

4. Appling the scientific method:
Observation: In 1972 Sherwood Rowland learned CFCs don’t break down well in the atmosphere. Problem: (page 14) What are the effects of CFCs in our atmosphere?

5. Gather information:
Nothing destroys CFCs in the lower atmosphere, they will rise
Solar radiation is intense in the upper atmosphere and will split CFCs

6. Hypothesis: CFCs break down in the upper atmoshpere and destroy ozone Predictions – what we expect to observe if the hypothesis is correct, often mathematical models are used 1. Chlorine monoxide will be present in the upper atmosphere 2. more CFCs will be present in the lower atmosphere

7. How is this a controlled study?
Test the hypothesis: controlled studies , all variables are constant except one
Experiment
Observational studies: observations will confirm or contradict the predictions
CFC concentrations were checked at
many levels throughout the atmosphere
How is this a controlled study?
All measurements were taken the same way, just at different altitudes

8. Analyze Data: Quantitative data supported the hypothesis
Analyze Data: Quantitative data supported the hypothesis. More CFCs were found at lower levels, more chlorine monoxide at higher levels. Conclusion: CFCs are destroying the ozone layer Why is this a problem? (page 3)

9. The ozone layer blocks Ultraviolet Radiation from reaching Earth’s surface
UV causes skin cancer and cell mutations
When did Molina and Rowland publish their results?
1974
When was the ozone hole over Antarctica discovered?
1985
Molina and Rowland shared what reward?
1995 Nobel Prize in Chemistry

10. What was the result of the discovery of the ozone hole
What was the result of the discovery of the ozone hole? Nations agreed to phase out CFCs When do scientists estimate the ozone layer will recover? 2050 What environmental issue today requires international cooperation? Climate change

11. Why were nations able to agree to stop CFC production in the 1980’s, but now cannot agree about climate change?