chemistry c1

1. how much nitrogen is in the atmosphere (7, 5, 7)
4. when the plants died they were buried under layers of sediment, what did the carbon that the plants took up turn into (6, 5)
5. after things cooled down what kept forming (9)
6. what did the water vapor do when the earth cooled (8)
7. how much oxygen is in the atmosphere (6, 3, 7)
9. what did the build up of oxygen in the atmosphere kill off (5, 9)
10. how was the build up of oxygen in the atmosphere a good thing as they were killing off early organisms. what were the other organisms called (7, 9)