Science Crossword Puzzle

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Across
  1. 5. H2O is also known as this (5 letters)
  2. 6. Organ that pumps blood (5 letters)
  3. 7. Not a proton or electron (7 letters)
  4. 9. Animals that eat only meat (9 letters)
Down
  1. 1. Centre of an atom (6 letters)
  2. 2. Gas used in photosynthesis (6 letters)
  3. 3. Used to measure heat (11 letters)
  4. 4. Opposite of solid (3 letters)
  5. 8. The green pigment in plants (7 letters)