Two cans full of water in the sun (Grades 1- 8).
Objective:
Students experience an example of how a shiny surface reflects light and a dark surface absorbs it.
Materials:
Procedure:
Fill the cans with water from the same source. Leave the thermometers in the water and have students describe and write all the similarities and differences between the two cans that they can notice. When the thermometers have adjusted have several students verify that the two thermometers read the same. Record the temperature and the time. Put away the thermometers. Take the cans outside where they will be in full midday sun and not molested. In two hours go outside and feel the difference in temperature by placing a hand in each at the same time. Put the thermometers back in the cans and see the difference! I put my students in one line and let each have a turn to use both hands. The shiny can acts like a mirror and it stays cool. The flat black can absorbs the heat. When our class did this there was a difference of 10 degrees after two hours on a warm day.
Close:
Take the materials and the class back inside and ask the students which can is most like a mirror and which is most like a towel? Respond to the recordings in the journals. Did both cans heat up or just one? The dull black can is like a heat sponge when left in the light. Many homeowners are already using this idea to heat a portion, if not all, of the hot water they use. How could we save energy by heating water from the sun?
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