Science Activity: Which Color Works Best for Solar Heating

Have students read the following activity and then discuss the following.

• Discuss reflection and absorption as they relate to other kinds of energy, such as sound.
• Disucss how the water gets heated, both directly and indirectly by conduction from the plastic.
• Disucss how the time of the year might affect the data.

Materials needed:

• four pie tins
• four pieces of flexible plastic, one in each of these colors: white, black, brown, and green
• scissors
• water
• thermometer
• graph paper
• four pencils of different colors
• copy of data table

Preparation

Cut each of the plastic pieces so that they completely cover the bottom and sides of a pie tin. Make sure to cover all of the metal.

The data table will be used to record the temperature measurements. The information will then be used to graph each of the colors that you measure.

1. Place a different color of plastic into each of the pie tins.
2. Find a sunny location where all the pie tins can be placed together. Make sure that ll four tins receive an equal amount of sunlight.
3. Fill each pie tin half-full with cool water.
4. Measure the water temperature in each pie tin, and record it in the table.
5. Continue to measure the water temperature for each color at 10-minute intervals for 40 minutes. Record your temperature measurements in the table.
6. Graph the measurements for each of the colors on graph paper. Use a different colored pencil to graph each color of plastic. On the x-axis, place the time measurements. On the y-axis, place the temperature measurements.

1. Which color caused the water to heat up the fastest? Which color caused the water to heat up the slowest? (Answers should agree with recorded observations. In general, the tins with lighter colors should heat up more slowly than the ones with darker plastic.)
2. Which color caused the water to reach the highest temperature? (The tin with the black plastic.)
3. Which color caused the water to remain at the coolest temperature? (The tin with the lightest (white) remained coolest.)
4. Identify the variables in this activity. (color of plastic, time in the sun, temperature of water, amount of water, amount of sunlight received)

How quickly does each color collect and hold heat from the sun? Have students write a short paragraph to compare and contrast how the different colors heat up.

For an extension activity, students can test each of the four colors without using water. Does the water make a difference in how quickly the colors heat up? Explain. (The plastic should have heated faster without the water because raising the temperature of the water requires more kinetic energy than heating the air and plastic surface.)