science vocab.

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Across
  1. 3. when particles are compressed together and don't move much
  2. 4. the basic unit of matter
  3. 6. when particles are close together but move past each other
  4. 7. amount of mass given in an amount of space measured in mass and units
Down
  1. 1. are far apart and don't stay in contact
  2. 2. motion of energy
  3. 5. two or more atoms joined by chemical bonds