Questions: The Water Cycle

Question 1

What happens to a puddle on a warm, sunny day? Where does the water go?

• A. The ground absorbs all of it
• B. The sun heats the water, turning some of it into invisible water vapor that rises into the air (evaporation)
• C. The water disappears and is gone forever
• D. The wind blows it away to another place

Answer: (B)

When the sun heats a puddle, water molecules at the surface gain enough energy to escape into the air as invisible water vapor. This is evaporation. The water has not disappeared -- it has changed from liquid to gas and is now in the air. Some water also soaks into the ground, but evaporation is the main reason puddles shrink on sunny days.

Question 2

The water you drink today could be the same water that dinosaurs drank millions of years ago.

• T. True
• F. False

Answer: True

Earth has had roughly the same amount of water for billions of years. Water is never created or destroyed -- it just cycles through different forms (liquid, gas, solid) and different places (oceans, clouds, rivers, underground). The water molecules in your glass have been through the water cycle countless times, and some of them were indeed around during the age of dinosaurs.

Question 3

Describe the three main steps of the water cycle and what happens in each one.

Model answer: 1. Evaporation: The sun heats water in oceans, lakes, and rivers, turning it into water vapor (gas) that rises into the air. 2. Condensation: High in the atmosphere, the water vapor cools and turns back into tiny liquid water droplets, forming clouds. 3. Precipitation: When enough droplets collect and grow heavy, they fall back to Earth as rain, snow, sleet, or hail. Then the water flows back to bodies of water and the cycle repeats.

These three steps -- evaporation, condensation, and precipitation -- form the core of the water cycle. The cycle is powered by the sun's heat and is continuous, with no beginning or end.