How is ozone formed in the upper atmosphere? Why is its depletion a cause for concern, and what has been done about it?

1. 1 · Show the formation. UV splits oxygen: O₂ → O + O. Then O + O₂ → O₃.
2. 2 · Give its role. The ozone layer absorbs harmful UV radiation, which can cause skin cancer.
3. 3 · Name the cause of depletion. CFCs used as refrigerants and in fire extinguishers; ozone levels fell sharply in the 1980s.
4. 4 · State the action taken. In 1987 UNEP got countries to freeze CFC production at 1986 levels, and CFC-free fridges are now required.
5. 5 · Real life. Choose CFC-free appliances and protect your skin from strong sun.
6. 6 · Close in one line. Protecting the ozone layer protects all life from UV rays.

Scoring tip: Write both equations, and name UNEP and the year 1987. These are the scoring points.