Directions Paint the outside of two of the cans one with white paint, one with black paint. Fill each can with the same amount of water (use a measuring cup) from the faucet. Place the cans on a sunny window ledge or in the sun somewhere. Let them sit for about three hours. Now take the temperature of the water in each can. Which can has the warmest water? Why was this so? Explain to your child the principle of solar energy and its benefits.