When Erasto Mpemba was in high school, the Tanzanian student asked a visiting professor, Denis Osborne why hot (212° F) water would freeze faster than warm (95° F) water. Osborn did not have an immediate explanation but had a technician perform the experiment in his lab. The technician confirmed that the hotter water did indeed freeze faster than the cooler water.
Mpemba was not the first to have discovered this effect. Aristotle, Francis Bacon, and René Descartes also made similar observations.
Does the Mpemba effect always occur? No. It depends on gas and dissolved mineral content in the water, container size, composition, and shape, and the environment around the container of water. The reasons for the Mpemba effect aren’t well understood, nor or the conditions under which it occurs. Some factors put forth to explain it are evaporation, dissolved gases and minerals, temperature distributions in the water, supercooling, and changes to the surrounding environment.
Wednesday, January 12, 2011
A cool(ing) trick
McMurray Hatchery blog (if you are into chickens, it's a site you MUST visit), written by Matthew Pressly. While it doesn't have a lot to do with cooking, it may have some applications in the kitchen (when making ice cream, ice cubes, etc.).