Across
- 2. plantsproduceoxygen
- 3. circulationofwaterthroughearth
- 6. fuel naturalfuel
- 7. watermovementthroughplants
- 9. colorlessgas
- 10. wateronearthsurface
- 12. waterthatfallsfromclouds
Down
- 1. gastoliquid
- 4. liquidtogas
- 5. microscopicorganisms
- 8. layerofgasaroundearth
- 11. closedsystemwithlivingthings