puzzle

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Across
  1. 3. tightly packed molecules
  2. 5. pure substance made of 1 type of atom
  3. 6. far apart molecules
  4. 8. negative charge
  5. 10. positive charge
  6. 11. loosely packed molecules
Down
  1. 1. 2 or more substances physically combined
  2. 2. our unit
  3. 4. neutral charge
  4. 7. building block of life
  5. 9. 2 or more elements chemically combined