Biology

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Across
  1. 3. a thing that is composed of two or more separate elements.
  2. 6. the action or process of observing something by sense organ.
  3. 7. a substance that increases the rate of a chemical reaction.
  4. 9. bond type of linkage formed from the electrostatic attraction between oppositely charged ions in a chemical compound.
Down
  1. 1. a substance which slows down or prevents a particular chemical reaction.
  2. 2. an idea or explanation for something that is based on known facts but has not yet been proved.
  3. 3. the smallest structural unit of an organism.
  4. 4. the process of increasing in physical size.
  5. 5. an individual animal, plant, or single-celled life form.
  6. 8. the basic unit of a chemical element.