SCIENCE FILE: An exploration of issues and trends affecting medicine, science and the environment

Q: Does hot water freeze faster than cold?

A: Yes, if you start out with identical volumes of water in containers of the same shape. According to researchers at San Francisco’s Exploratorium, there is some controversy about why this occurs, but the most likely explanation is evaporation. Hot water evaporates more rapidly than cold. Soon after you put your containers in the freezer, you’ll have less water in the one that originally held hot water, so it will not take as long to freeze. Evaporation also absorbs a large quantity of heat, cooling the liquid.