How Can You Get the Most Heat Energy from the Sun?

Materials Needed
• Three identical jars per small group
• Paper and pencils
• Black paper
• Aluminum foil
• Tape
• Three thermometers per small group
• Sand

Procedure
1. Fill the three jars with sand.
2. Cover one jar with black paper, including the top, and tape the paper in place.
3. Cover the second jar with aluminum foil, including the top, and tape the foil in place.
4. Leave the third jar uncovered.
5. Record the temperature shown on the thermometers. Be sure all three indicate the same temperature.
6. Insert one thermometer into the sand in each jar. With the two covered jars, puncture a hole in the top covering and insert the thermometer through the hole.
7. Place all three jars in sunlight. All should receive the same direct sunlight.
8. Check and record the temperature of the three thermometers every 15 minutes for about two hours.
9. How do the temperatures compare? What can you say about the effect of a black surface and a shiny surface on absorption of energy from the sun?
10. Remove the jars from the sunlight and continue to record the temperatures of the three thermometers for two more hours.
11. How do the temperature changes compare? What can you say about the effect of a black surface and a shiny surface on heat loss?

For Problem Solvers
Here are more ways to compare the effect of color on heat absorption. Place a thermometer on a paper plate and lay a sheet of black paper over it. Prepare a second plate using a thermometer and white paper, then a third using aluminum foil. On a warm, sunny day, place all three plates in direct sunlight being sure all papers are facing the sun at the same angle. Check and record the temperatures on the thermometers after one-half hour, then again after one hour.
If you live in a cold climate, place papers of various colors on a snow bank, in the sunlight. Use a black paper, a white paper, and a piece of aluminum foil of the same size. Use other colors also if you’d like to. Line them up so they all have direct sunlight and all papers are facing the sun at the same angle. After an hour, check the snow under the papers to find out how much has melted. Check them again after two hours.

Teacher Information
The uncovered jar of sand will provide a control to help students observe the effect of both the black surface and the reflective surface. The temperature of the jar with the black surface will likely increase noticeably faster than that of the other two. The foil will reflect heat, and the temperature increase of the sand covered by it will be very slow.
Buildings in warm climates are typically covered with light-colored materials or light-colored paint. Astronauts wear reflective clothing to help protect them for the direct rays of the sun.

Science Process Skills
Observing, inferring, classifying, measuring, predicting, communicating, comparing and contrasting, using space-time relationships, formulating hypotheses, identifying and controlling variables, experimenting