Just a bunch of words

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Across
  1. 5. The measurement of kinetic energy.
  2. 8. The result of elements being mixed together.
  3. 9. The smallest bit of matter.
  4. 10. A substance made of one type of atom.
  5. 11. This is a free space, literally, the answer is free.
  6. 12. What you say when someone is leaving.
Down
  1. 1. When a mixture looks different throughout.
  2. 2. When a mixture looks the same throughout.
  3. 3. What's the ______ with you?
  4. 4. Whatever is at the end of this sentence.
  5. 6. Solid, liquid, gas.
  6. 7. A mixture of matter.