What is the Atmosphere?

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Across
  1. 4. the invisible gaseous substance surrounding the earth, a mixture mainly of oxygen and nitrogen.
  2. 7. the basic unit of a chemical element.
  3. 10. ______________ is responsible for nearly all of the oxygen currently found in the atmosphere.
  4. 11. the strength and vitality required for sustained physical or mental activity.
  5. 12. rain, snow, sleet, or hail that falls to the ground.
Down
  1. 1. Animals convert sugar into food energy they can use.
  2. 2. A body ___________ above the normal is a fever.
  3. 3. an individual animal, plant, or single-celled life form.
  4. 4. Made up of gases that are essential for photosynthesis and respiration.
  5. 5. a colorless, odorless reactive gas, the chemical element of atomic number 8 and the life-supporting component of the air.
  6. 6. The planet we live on.
  7. 8. Without _____ for protection only the simplest life forms would be able to live on earth.
  8. 9. a continuous area or expanse which is free, available, or unoccupied.