Scientific Crossword

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Across
  1. 3. A chemical reaction that releases energy
  2. 6. A force that pulls objects towards the center of the Earth
  3. 7. A type of energy produced by the nucleus of an atom
  4. 8. The study of Earth and its atmosphere
Down
  1. 1. The building blocks of proteins
  2. 2. The study of living things
  3. 4. A substance that changes the rate of a chemical reaction
  4. 5. The smallest unit of matter
  5. 6. The process by which living organisms develop from an embryo
  6. 9. The basic unit of heredity