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Weather theoryQuestion 305 of 934

Why does warm air rise?

  1. Heat packs the air molecules together, so the air is heavier
  2. Heat adds mass from the sun, so the air floats above cool air
  3. Earth's rotation pulls the warm air up from the surface
  4. Heat spreads the air molecules apart, so the air is less dense
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Correct answer: Heat spreads the air molecules apart, so the air is less dense

Expanding air becomes less dense and lighter than the air around it.

Source: Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25C), Chapter 12: Weather Theory — Atmospheric Circulation, page 287

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Questions last reviewed: 18 October 2026