This is my crossword puzzle demetrus

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Across
  1. 2. a chemical that gives off heat
  2. 4. a substance formed before chemical reaction
  3. 5. a chemical that absorbs heat
  4. 7. a chemical reaction
Down
  1. 1. a process that changes a substance into a new substance
  2. 3. a substance formed during a chemical reaction
  3. 6. a matter that don't affect its form
  4. 8. a material that takes space