Did You Know: Hot Water Freezes Faster than Cold?

On its way to freezing, surely hot water has to pass through a point where its temperature is the same as the cooler water and after that point both should freeze at the same rate? And that would mean that the cold would freeze quicker than the hot? Right?

Despite the fact that this might not seem right at first, numerous experiments have shown that it is the case. It has, in fact, been well documented in history by Aristotle, Bacon, and Descartes but it wasn’t till it was rediscovered by a Tanzanian school boy called Mpemba that scientists really got involved in the debate. This effect still leaves scientists pretty divided and no one really knows why it happens.

What happened was that, one day, Mpemba was making ice-cream and he noticed that hotter liquids could freeze faster than cold. So he told his teachers and they, most probably being far too concerned with wanting to eat the ice-cream in question, chose to not believe him. It wasn’t till later when visiting Britain’s repeated his experiments that people realized he hadn’t been overdosing on sugar and was actually right.

So, if you start with two identical volumes of water and freeze them in exactly the same way with the only difference being that one starts at a higher temperature, how on Earth can the hot one freeze sooner than the cold? There are a number of theories that can possibly explain this phenomenon, although it may be a combination of effects each playing a role.

© 2012 SAT Telecommunications Ltd.

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