Talk It Over

Which keeps you cooler on a hot day, a black shirt or a white shirt? What about other colors? How can you find out?

Get

• Black and white construction paper
• Ruler
• Scissors
• Tape
• 2 digital instant-read thermometers*
• Sunny spot or gooseneck desk lamp
• Clock or timer
• Other colors of construction paper to test

Go

1. Cut pieces of black and white construction paper that measure approximately 10 cm x 20 cm (4" x 8"). Fold in half along the length and tape the sides. You have made pockets that the thermometers can fit in.
2. Put the thermometers in the pockets. Turn them on and read the beginning temperature. They should read the same. Turn them off to save battery power.
3. Place the thermometers in a sunny place or under a gooseneck desk lamp. After 10 minutes and without moving the thermometers, turn them on and read the temperatures. Turn them off.
4. Take additional temperature readings every 10 minutes for 1 hour.
5. Repeat steps 1–4 with other colors you would like to test.

Stay Safe

Be careful with a desk lamp. A hot bulb can burn your fingers!

Go Easy

Follow the "Go" procedure, but read the temperature only twice: once before you begin and again after 1 hour. Use subtraction to find out which temperature changed most. Try to explain why.

Go Far

The heat absorption properties of colored materials depend on many factors, including how much light is reflected and what wavelengths of light (colors) are absorbed. Use the "Go" procedure to test different materials of the same color. Also, you might approach the question a different way. Try to find which colors and materials work best as insulation, reducing heat loss. Make some telephone calls to see whether you can borrow a pyranometer from a commercial or college laboratory. A pyranometer allows you to measure albedo, the amount of light reflected from a surface. Perhaps you can find a way to relate albedo differences to your heat data.

Show Your Results

Record temperatures in a data table like this for "Go":

Make a line graph that shows how temperature changed over time. Use different colored lines on the graph to represent the colors of the papers you tested.

For "Go Easy," put your data in a table like this:

Make a bar graph of your data. Write a sentence that describes and explains any differences.

For "Go Far," make data tables and line graphs as for "Go." Try to explain the differences you find in the heat absorption or insulating abilities of materials of the same color. If you measure albedo, try to answer the following question: Do materials with greater albedo absorb more or less heat?

Tips and Tricks

• If you use a gooseneck lamp, the bulb should be at least 100 watts. Bend the neck of the lamp so that the bulb is close above the thermometers. Make sure its light falls evenly on both.
• Many thermometers read temperatures in both Fahrenheit (°F) and Celsius (°C). You can use ither for this experiment; just be careful not to confuse them. If you want to work as scientists do, use °C.
• You'll get better results if you conduct several trials and average your data.

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