Which phenomenon states that hot water can freeze faster than cold water?
The Mpemba effect is a process in which hot water can freeze faster than cold water. The phenomenon is temperature-dependent. There is disagreement about the parameters required to produce the effect and about its theoretical basis. The Mpemba effect is named after Tanzanian scientist Erasto Bartholomeo Mpemba who discovered it in 1963. There were preceding ancient accounts of similar phenomena, but these lacked sufficient detail to attempt verification. The phenomenon, when taken to mean "hot water freezes faster than cold", is difficult to reproduce or confirm because this statement is ill-defined.
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6 Comments
Gwyn Hill
What is going on? I answered this question yesterday!
Eric Arvidson
This is demonstrated by videos showing people in Minnesota and Alaska taking a pan of boiling water and going outside in -30degree F temps: throwing the pan in the air. The resultant mist and snow prove the idea.
Vance Duncan
I wonder if it has something to do with water’s density profile. It is one of the only elements - I’m not sure if there are others - that has lower density both at low temperatures and high temperatures. That is why ice floats and steam rises.
Allan Berry
In Canada, arenas with artificial ice were often resurfaced using hot water. I remember some know-it-all kid saying, "It's because hot water freezes faster." It didn't make much sense to me then. I have a feeling that warmer water was used because it would result in ice that was not as brittle or subject to cracking.
Keith Richard Mears
He was a Tanzanian high school student at the time of his observations, not a professor.
schaeffer
If you throw cup of hot water in the air when temperatures are below freezing (ideally below 20°F. The water will freeze before starting to fall down. This is also used on ski trails to add SNOW