Chapter 1 - Planet Earth

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Across
  1. 1. Chemical formula for carbon dioxide
  2. 3. A gas that is produced by animals such as cows
  3. 6. The name given to the chemical with the formula NH3
  4. 7. Water in a gaseous state
  5. 12. A gas that can be used in the treatment of water
  6. 14. In human terms, ____ are materials we get from the environment to meet our needs
  7. 15. A substance that can be used in a fuel cell to power cars and other automobiles
  8. 19. In some parts of the world, seawater is made drinkable by ____?
  9. 20. Name of the element with the symbol C
  10. 21. Another name for calcium carbonate
  11. 23. Term used for describing a chemical reaction that releases heat
  12. 24. The process by which a solid may be transformed directly to a gas without passing through a liquid state
Down
  1. 2. Name of the element with the symbol O
  2. 4. A chemical substance that is added to fertilisers that provides plants with nitrogen
  3. 5. A gas found in air with a boiling point of approximately -196 degrees Celcius
  4. 8. Name of the element with the symbol Cl
  5. 9. Chemical formula for nitrogen dioxide
  6. 10. A neurotoxic metal
  7. 11. The process by which plants absorb H2O and CO2 to form sugar and oxygen (with the help of sunlight and a catalyst)
  8. 13. A noble gas with a boiling point of approximately -108 degrees Celcius
  9. 16. Catalytic converters may be attached to the ____ systems of cars
  10. 17. A type of fossil fuel
  11. 18. The distance from the earth's surface to its ____ is over 6000 km
  12. 22. Another name for calcium oxide
  13. 25. Water in a frozen state