Chemistry crossword

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Across
  1. 2. organic catalysts
  2. 7. mixtures
  3. 10. period
  4. 11. H2O
  5. 13. mass
  6. 15. a table of chemical elements
  7. 17. charged atom
  8. 18. groups
  9. 19. mass number-atomic mass
Down
  1. 1. fire
  2. 3. releases heat energy
  3. 4. workplace hazardous materials information system
  4. 5. shinny
  5. 6. oxygen combines with a substance
  6. 8. absorbs heat
  7. 9. burning
  8. 12. reaction
  9. 14. physical substance
  10. 16. air combine with metal