Across
- 3. inhale
- 4. exhale
- 6. a lot of this gas is in the stratosphere
- 8. light shining on plants
- 9. vary in concentration
- 12. Conduction convection and radiation
- 14. When water dissolves it becomes this
- 15. cow farts
Down
- 1. Nitrogen oxygen and argon
- 2. symbol:N Atomic number:7
- 5. the sky
- 7. gram and pounds
- 10. a gas that is everywhere
- 11. elements in group 18 on periodic table are this
- 13. Methane is one of these