Questions: The Water Cycle

Question 1

What causes water from a lake to enter the atmosphere and eventually form clouds?

• A. The wind blows the water straight up into the sky
• B. The sun heats the water, it evaporates into vapor, and the vapor rises and condenses into cloud droplets
• C. Fish push the water out of the lake and into the air
• D. Clouds suck water up from the lake like a vacuum

Answer: (B)

The sun's heat provides energy for liquid water to evaporate from the lake's surface. The invisible water vapor rises because warm air is lighter. As it reaches higher, cooler air, the vapor condenses into tiny liquid droplets that we see as clouds.

Question 2

Clouds are made of water vapor.

• T. True
• F. False

Answer: False

False. Clouds are made of tiny liquid water droplets or tiny ice crystals — not water vapor. Water vapor is invisible. The vapor condensed into visible droplets to form the cloud. If clouds were vapor, you would not be able to see them.

Question 3

Name the three main steps of the water cycle in order.

Model answer: Evaporation, condensation, and precipitation. Water evaporates from bodies of water, the vapor condenses into clouds, and water falls back to Earth as precipitation (rain, snow, or hail).

The water cycle is driven by heat from the sun. Evaporation moves water from liquid to gas, condensation moves it from gas back to liquid (as clouds), and precipitation brings that liquid (or solid, as snow) back to the ground. Then it starts over.