Chemistry crossword puzzle

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Across
  1. 6. continuous physical force exerted on or against an object by something in contact with it
  2. 7. electrically neutral particles
  3. 8. negatively charged ion
  4. 9. a reaction accompanied by the absorption of heat
  5. 12. a science experiment that involves the use of fire
  6. 13. having a pH lower than 7
  7. 15. formula of a chemical compound is the simplest whole number ratio of atoms present in a compound
  8. 16. the emission of energy as electromagnetic waves or as moving subatomic particles
  9. 17. the degree or intensity of hotness or coldness present in a substance or object, especially as expressed according to a comparative scale
  10. 18. formed by the electrostatic attraction of oppositely charged ions
Down
  1. 1. a collection of particles called protons, which are positively charged, and neutrons, which are electrically neutral
  2. 2. the amount of space that a substance or object occupies
  3. 3. volume × density=
  4. 4. negatively charged particles
  5. 5. positively charged particles
  6. 6. ideal gas law
  7. 9. a measure of the attraction of an atom for bonding electrons in molecules compared to that of other atoms
  8. 10. rings that hold electrons
  9. 11. a reaction accompanied by the release of heat
  10. 14. a positively charged ion