Firefighters and chemical reactions

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Across
  1. 3. What can be used to put out a fire?
  2. 4. dioxide What gas is released when something burns?
  3. 5. What is fire an example of?
  4. 6. A change of state from a liquid to a gas
  5. 9. A change of state from a solid to a liquid
  6. 11. The amount of energy required to start a chemical reaction
Down
  1. 1. A chemical reaction which absorbs more energy than it releases
  2. 2. What is the device that makes a loud sound to warn about a fire called?
  3. 3. What is the opposite of "flammable"?
  4. 7. What tool do firefighters use to break through doors and walls?
  5. 8. What gas is required for fire?
  6. 10. What is the chemical symbol for water?
  7. 12. A chemical reaction which releases more energy than it absorbs