Science Crossword Puzzle

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Across
  1. 2. the opposite of a physical reaction
  2. 6. one of the healthiest drinks
  3. 7. when something isn't finished
Down
  1. 1. without it most transport cannot move
  2. 3. another word for done
  3. 4. the opposite of a chemical reaction
  4. 5. a compound of oxygen with another element