Ozone and the Scientific Method

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)

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

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?

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

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

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

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)

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

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

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