The crossword

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Across
  1. 3. A topic in science starting with a "C"
  2. 5. Some people may have a talent in this
  3. 6. Existing in the state of a gas
  4. 8. A body of myths
Down
  1. 1. Having a form of a circle, round
  2. 2. Do a lot of experiments and are very smart
  3. 4. You didn't understand something properly
  4. 7. A colourless, odourless, flammable gas that combines chemically with oxygen to form water
  5. 9. Someone or something that observes