Learners make a refrigerator that works without electricity. The pot-in-pot refrigerator works by evaporation: a layer of sand is placed between two terra cotta pots and thoroughly soaked with water. The contents of the inner pot are covered with a wet cloth. As the water evaporates, it cools the contents. If more water is added, the cooling can be maintained for some time. The lesson plan includes handouts, background information, and suggested extension activities.