Black absorbs heat better than aluminum foil. The foil reflects the light away.
Two cans full of water in the sun (Grades 1- 8).
Depends on warm sunny weather. Should be started early in the morning, the cans should be placed in a sunny spot with full sun.
Objective:
Students experience an example of how a shiny surface reflects light and a dark surface absorbs it.
Materials:
A pair of thermometers.
A pair of coffee cans or other large metal cans (size of paint gallons) , Cover one of the cans and the other should be painted a flat black. Glossy black paint won't work as well as flat.
Aluminum foil, Enough to cover one of the cans.
A sunny day , good luck
Water
Journals- pencils
A mirror (option for making connections to reflection of light)
A dark towel and a white towel ( optional version 2)
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 turned over. 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 fingers from 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.
Version 2 - Lay out a black towel and white towel in the same area with full sun on a warm day. Students line up and take a turn touching each towel with a different hand.
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?
Summarize the conversation and write what we learned. What did we do and what did we learn? Students write their descriptions in journals. When finished, a student reads their entry to three other students.