CROSSWORD TIME!!!!

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Across
  1. 2. the process by which complex organic substances are broken down into simple organic matter.
  2. 3. the ability of a mineral to resist scratching
  3. 9. a chart that arranges all the known elements according to their atomic number
  4. 10. substance made up of one type of atom
  5. 11. the temperature at which a solid melts to liquid
  6. 13. positively charged particle
  7. 14. proteins that act as a biological catalyst
  8. 15. the smallest unit in an element
Down
  1. 1. minimum energy required to start a reaction
  2. 4. an alloy of carbon and iron
  3. 5. vertical column in the periodic table
  4. 6. a group of atoms bonded together
  5. 7. the amount of mass per unit volume
  6. 8. the second most abundant mineral in the earth's crust
  7. 12. atoms of the same element that contain different numbers of neutrons