# 28. SOLAR HEATING AND COOLING

SUBJECT: Science
GROUP SIZE: Small or Large
TIME: 2-60 minute periods
TYPE OF ACTIVITY: Student Investigation
TEACHING STRATEGY: Open or Guided Discovery
CONCEPTS: Heat Reflection Absorption Solar Cooling
SKILLS: Hypothesizing Experimenting Interpreting Data

Objective: To set up an experiment to determine what colors and or materials reflect the most heat away from an enclosed container.

Materials: Three small corrugated cardboard boxes; several colors of construction paper or paint (be sure to include white and black); aluminum foil; three thermometers; clear sheet of acetate or plastic (overhead projection acetate is fine); tape.
Teacher Background Information: One of the major obstacles to living in space is temperature control. The temperatures inside a spacecraft may reach several hundred degrees if some method of cooling is not put into place. The early Skylab missions used a slow rate of rotation and shading as techniques to help cool. The Lunar Lander used gold foil on the outside to reflect heat away from vital components. Of course, air conditioning units are also carried aboard spacecraft as well as in space suits. However, if a spacecraft must remain in one place for any length of time, some method of assisting the cooling process must also be used.
Procedure:

Have the students speculate on how to go about testing for the cooling characteristics of several materials and colors on a closed container. Tell them to use containers which are about 15cm x 25cm x 5 to 1Ocm.

If you wish to make this a bit more directed activity, you may have them do the following: Construct three boxes which have a small hole punched in one end to allow the thermometer to be inserted. Place a sheet of colored paper on one side of the box and face this to the sun for about 30 minutes. Have the students record the temperature inside the box every 10 minutes. Try placing acetate over the colored paper and record the results including any differences in temperature from plain paper. Try foil and or several other materials, recording the results each time. Try lining the inside of the box as well as the outside with different materials. After all the trials, have the students graph their results and present their conclusions as to the best reflective material for heat dissipation.

During the 10 minute periods the students are waiting to record temperatures in the container, have them use another thermometer to measure the temperature near buildings, rocks and other structures where the sunlight falls at different angles or, in some cases, not at all. Have the students relate these readings to the effect of the angle of the sun on temperature. How might the angle of the sun affect the temperature inside their box?
Extensions:

• (1) If you have access to an electric spit from a barbecue or a turntable device, have the students measure the temperature inside a container mounted on the device and compare the results with the other trials.
• (2) See other solar experiments in the Earth Science section of this manual.
• (3) The students may wish to use their data to construct a device to retain as much heat as possible for a solar energy heat source or cooker.
• (4) Check out Activity #83 – “Shielding Against Heat and Cold” in the K – 6 COME FLY WITH ME materials.

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