Across
- 1. What animals breathe in
- 4. The process of burning
- 5. What animals breathe out
- 6. The action of breathing
- 8. The process animals use with sunlight
- 9. To separate the natural products from the raw materials.
- 10. Increasing density
Down
- 2. The natural substance plants make
- 3. A natural fuel
- 5. CO2
- 7. The opposite of plants
- 8. The opposite of animals