Sunday, June 18, 2017

IS THIS THEORY IN HOT WATER?

Apparently, there is much we do not understand about water, including how and when it freezes. One uncertainty is whether the so-called "Mpemba effect" really exists.

In the 1960s, a Tanzanian student named Erasto Mpemba is said to have noticed that very hot ice cream firmed up more quickly when placed into a freezer.* It is not clear whether the ice cream was vanilla, chocolate or fruit or nut flavored. Mr. Mpemba's name has become attached to an extrapolated phenomenon that hot water can freeze faster than cold water.

According to a recent article, the Mpemba effect is the focus of much research and debate.* A new study suggests that hydrogen bonds in water change, with weaker bonds breaking, as water is heated , causing molecules to form fragments that can realign to initiate freezing. Cold water requires weak hydrogen bonds to be first broken to enable molecule realignment and freezing to take place.

However, some throw cold water on the hot water theory. The article quotes some sources which question whether the Mpemba effect actually exists. It cites experiments with hot and cold water which allegedly resulted in no observation of the effect.

However, a chemist criticized these experiments because they did not observe the time of initiation of freezing. He allegedly acknowledged that because freezing of water is a complex process which is difficult to control, it is hard to verify. However, he is quoted as being convinced that hot water can freeze quicker than cold water.*

One thing of which I am sure--my ice cream cone melts more quickly when it is hot outside than when it is cold. The smudges over my face and the drips on my shirt prove this. I call it the "Kucera effect". Can we extrapolate that ice melts more quickly in hot weather than cold weather? More research may be needed.

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*Conover, "Fast-freezing Hot Water Spurs Debate",
Science News, February 4, 2017, p. 14

© Daniel J. Kucera 2017

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