Describe the process from evaporation to precipitation in detail, and explain why clouds become heavy.
Answer
Sun heats the surface, causing evaporation of water into the air. The rising vapour cools, condenses on tiny particles forming cloud droplets. As more water condenses, droplets grow and coalesce; when their combined weight overcomes the lift of warm air, gravity pulls them down as rain. Clouds become heavy when droplet size increases and the number of droplets rises, making the cloud's mass exceed the supporting buoyant force.
Step-by-step solution
- 1. Sun heats the earth’s surface and evaporates water into the air.
- 2. The vapour rises; as it goes up, the temperature falls and the vapour condenses on dust or pollen particles, forming tiny cloud droplets.
- 3. Droplets collide and combine; their size and mass increase.
- 4. When the mass of the droplets exceeds the buoyant lift provided by warm rising air, gravity pulls them down as precipitation.
- 5. The cloud becomes heavy because more droplets have formed and grown larger, increasing the cloud’s overall weight.
Common mistake: Neglecting the role of gravity or the growth of droplets
Concept tested: Evaporation, condensation, precipitation
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