Observations and results
Was the black box the hottest and the white box the coolest, with the gray box somewhere in between in temperature?
Just like keeping cool in a light-colored shirt on a hot day, the white box reflects more light than do the darker boxes. The white box should be the coolest inside, compared with the temperature in the shade nearby. The black box absorbs the most light, and this energy is transferred inside of the box over time and warms up the thermometer. The black box will probably be the hottest compared with the temperature in the shade. The gray box absorbs some light, so it will also be warmed up, but its temperature will be somewhere in between those of the black and white boxes. The reason that light-colored materials reflect more light than darker materials is actually rather complex but basically comes down to the number and type of chemical bonds in a material—these bonds affect what kind of light (specifically what wavelength) it absorbs. Some people and companies have also started adopting white roofs, which reflect much more heat than darker-colored roofs.
More to explore
Color and Energy Matters from Color Matters
Color and Vision: Light Absorption, Reflection and Transmission from The Physics Classroom
Energy-Efficient Paints for Your Home? from TheInfoMine
Can the Color of Your House Reduce Your Energy Bill? from Science Buddies
This activity brought to you in partnership with Science Buddies