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# Water Cycle

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Source:
Author: Janice VanCleave

So You Want to Do a Project about the 'Water Cycle!

### Purpose

To demonstrate the water cycle.

### Materials

• Transparent storage box about the size of a shoe box
• Ruler
• Sand
• Tap water
• 9-ounce (270-mL) plastic cup
• Plastic food wrap
• Ice cube
• Resealable plastic bag
• Medicine spoon (available at pharmacies and used to measure accurate doses)

### Procedure

1. Fill the box with 1 inch (2.5 cm) of sand.
2. Pour water into the box until the sand is thoroughly wet but doesn't have any water standing on its surface.
3. Set the cup in the center of the sand.
4. Cover the top of the box with plastic wrap.
5. Put the ice cube in the bag and seal the bag.
6. Place the bag in the center of the plastic wrap that covers the box.
7. Gently push the ice down about 1 inch (2.5 cm) so that the plastic wrap slopes down toward the center of the cup.
8. Set the box near a window so that the sunlight shines on the box.
9. Allow the box to sit undisturbed until the ice melts. This may take about 1 hour.
10. Remove the bag and tap the middle of the plastic wrap so that any water collected on its underside falls into the cup.
11. Remove the plastic wrap, then remove the cup.
12. Measure the amount of water collected by pouring it into the tube of the medicine spoon.

### Results

Water droplets form on the underside of the plastic under the ice. Most of these water droplets fall into the cup.

### Why

The heat from the Sun provides energy, causing some of the water in the sand to evaporate and form water vapor. This water vapor then condenses on the underside of the plastic, which has been cooled by the ice. As more water collects on the plastic, the droplets increase in size until their weight causes them to fall into the cup below. The falling water drops represent rain. This is a model of the water cycle (the cycling of water between Earth and the atmosphere) on Earth. The sand represents the surface of Earth, and the plastic represents Earth's atmosphere. As long as the box remains closed, the amount of water in the box remains the same; it just moves from one place to another by changing from one form to another.

### For Further Investigation

Does it rain more over the ocean or the land? A project question might be, How does Earth's surface affect the water cycle?

1. Repeat the investigation with boxes containing different surfaces. Replace the sand with different materials, such as moist soil, freshwater, and salt water. NOTE: Ocean water is the equivalent of about 1 tablespoon (15 mL) of table salt per 1 quart (1 L) of tap water.
2. Compare the amount of water in the glasses after the ice has melted.

### References and Project Books

Campbell, Ann-Jeanette, and Ronald Rood. The New York Public Library Incredible Earth. New York: Wiley, 1996.

Churchill, E. Richard. 365 Simple Science Experiments with Everyday Materials. New York: Black Dog & Leventhal,1997.

Mandell, Muriel. Simple Weather Experiments with Everyday Materials. New York: Sterling, 1991.

Suplee, Curt. Everyday Science Explained. Washington, D.C: National Geographic Society, 1998.

Time-Life Books. Planet Earth. Alexandria, Va: Time-Life Books, 1997.

VanCleave, Janice. Janice VanCleave's Ecology for Every Kid. New York: Wiley, 1966.

Janice VanCleave's Oceans for Every Kid. New York: Wiley, 1996.

Janice VanCleave's Science around the Year. New York: Wiley, 2000.