General science

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Across
  1. 4. makes windmills turn
  2. 7. balloons filled with
  3. 8. produce CFC
  4. 13. plants prepare food
  5. 14. energy from earth
  6. 15. removal of waste
  7. 17. our galaxy
  8. 19. unit of force
  9. 20. hottest planet
Down
  1. 1. biological mass
  2. 2. speed with direction
  3. 3. thermometer
  4. 5. length of shortest path travelled by a body
  5. 6. first element
  6. 9. path of light energy
  7. 10. plant science
  8. 11. smallest unit of matter
  9. 12. bending of light
  10. 16. Disease on global scale
  11. 18. eyeglasses