You really can freeze hot water faster than cold*

*But only if you’re a clever physicist and you bend the rules

4:36pm, March 23, 2010

Hot water really can freeze faster than cold water, a new study finds. Sometimes. Under extremely specific conditions. With carefully chosen samples of water.

New experiments provide support for a special case of the counterintuitive Mpemba effect, which holds that water at a higher temperature turns to ice faster than cooler water.

The Mpemba effect is named for a Tanzanian schoolboy, Erasto B. Mpemba, who noticed while making ice cream with his classmates that warm milk froze sooner than chilled milk. Mpemba and physicist Denis Osborne  published a report of the phenomenon in Physics Education in 1969. Mpemba joined a distinguished group of people who had also noticed the effect: Aristotle, Francis Bacon and René Descartes had all made the same claim. 

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