Matter!

1234567
Across
  1. 3. a bunch of different things put together
  2. 4. cannot be easily separated
  3. 6. stored energy
  4. 7. can be easily separated
Down
  1. 1. a combination of 2 or more pure substances
  2. 2. the energy of motion
  3. 5. made of itself and nothing else, also on the periodic table
  4. 6. this type of substance literally, can't be separated