BioEd Online

Teacher Background

We seldom think about the sun’s importance to our planet. It is the ultimate source of almost all the energy we use. Besides the sun, the only other sources of energy on the planet are radioactive rocks and the molten core deep below Earth’s surface. The sun keeps us warm. It is responsible for weather, which is caused by uneven heating of large masses of air. Our food and common fuel sources depend or depended on solar energy trapped by producers, such as plants.

This activity is designed to build student awareness of the importance of the sun as the ultimate source of almost all energy on Earth. It also provides insight into harnessing the sun’s power directly as a source of energy, as Mr. Slaptail does with his solar water heater in the Global Atmospheric Change unit's storybook, Mr. Slaptail's Curious Contraption.

Objectives and Standards

Concepts

• Some of the energy given off by the sun can be felt as heat.

• Heat from the sun can be used as a source of energy.

Science, Health, and Math Skills

• Measuring liquids

• Predicting

• Observing

• Comparing

• Drawing conclusions

Materials and Setup

Materials per Group of Students

• two 9-oz clear plastic cups

• graduated cylinder, 100-mL (or metric measuring cup)

• student thermometer, plastic

• copies of “Sunlight Observations” sheet

Setup

1. Place all materials in a central area for Materials Managers to collect for their groups. Have students work in groups of 4 to conduct the activity.

2. If you are teaching this activity during the winter, you will need to conduct it indoors in a sunny window. When the weather is warm, students may conduct the experiment outside.

Procedure and Extensions

1. Ask students, How do we get hot water in our homes? Does the water come that way or do we have to heat it? Lead students into a discussion about different energy sources, such as electricity or gas, that are usually used to heat water for houses.

2. Follow the discussion by asking, What if we didn’t have any electricity or fuel to burn? Are there other ways to heat water? Guide students into a discussion of the sun’s importance as a source of heat and other energy for Earth. Ask, How could we find out if the sun provides energy to heat water? Tell students they will be investigating this question.

3. Have each group of students label one of the cups "light” and the cup “dark.” Next, have them measure 50 mL of water into each cup.

4. Direct students to measure the temperature of the water in each cup and to record the temperature on their student sheets. Have each group place the cup labeled “light” in direct sunlight (outside or inside the classroom). The other cup should be left inside the classroom, preferably in a dark area, away from any heating vents or radiators.

5. Have students predict the final temperature of the water in each cup and write their predictions in the appropriate spaces on the “Sunlight Observations” sheet.

6. If possible, have students wait at least one hour before checking the “light” cup. Have them measure the temperature of the water in the cup and record it on their sheet. Afterward, have them measure and record the temperature of the water in the “dark” cup.

7. Ask, What happened to the water in the cup that you placed in the sun? Did it become warmer or colder or stay the same? What about the water in the cup you left inside? Help students understand that energy from the sun warmed the water in the “light” cup. Ask, Where are other places that we can observe energy from the sun?

Extensions

• Have students compare how different-colored cups absorb heat from sunlight, or examine the effects of placing the cups on a reflector made of aluminum foil or on black paper (which absorbs heat). Students may also want to compare results from cups placed on a grassy surface to those from cups sitting on a paved surface.

• Challenge students to come up with their own designs for solar water heaters. Let them draw their designs and/or build their heaters from recycled materials.

Handouts and Downloads