Two cans, one black and one reflective, are at room temperature. They are then exposed to a heat lamp. Which one heats up fastest? The cans are identical except for their surfaces.

1. the black can
2. the shiny can
3. they heat up at the same rate

We've probably all noticed, by leaving black objects out in the sun, that they heat up fastest. The black can absorbs radiation more efficiently than does the shiny can, which reflects most of the radiation away.

The same two cans are then filled with hot water. Which cools down fastest?

1. the black can (15/33) (46%)
2. the shiny can (7/33) (21%)
3. they cool down at the same rate (11/33) (33%)