Heat & Temperature

Water Freezer

This exhibit demonstrates that evaporation is a cooling process. A small amount of water is squirted into an evacuated chamber. Because there is no air pressure on the liquid, evaporation takes place at a much higher rate, sometimes even boiling the water (at room temperature!!!) Since only the faster molecules escape, leaving the slower ones behind, the liquid cools. After about one minute, the water begins to freeze over. It is quite a sight to see water boiling and freezing at the same time.