1. Which of the following chemical formulas represents the Nitrogen in the atmosphere?

2. What living organisms play an important role in helping Nitrogen change states in the soil?

3. Which process in the nitrogen cycle turns dead plants and animals into ammonium?

4. Which process in the nitrogen cycle turns ammonium into nitrates?

5. Which process in the nitrogen cycle takes extra nitrogen from the soil and puts it back into the air?

6. Which process in the nitrogen cycle turns nitrogen into ammonium?

7. Which process in the nitrogen cycle occurs when plants absorb nitrogen from nitrates in the soil?

8. In what way is nitrogen important to life on Earth?

9. True or False: Human activities such as nitrogen fertilizer can upset the balance of the nitrogen cycle.

10. Around what percentage of the Earth's atmosphere is nitrogen?