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Q & A: melting ice

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Most recent answer: 10/22/2007
Q:
how can you melt ice without using heat
- bob
A:
I guess that you mean: how could you melt the ice without warming it up?

You could put the ice in some salt water or sugar water or alcohol, etc. The melting point of water in solutions like that is lower than in pure water. So even if the solution is just as cold as the ice, unless the ice will at least partly melt until the solution becomes more dilute. When the ice melts, the solution will actually get colder. This is how homemade ice-cream makers produce a bath of icewater that's colder than the freezing point of pure water, which is needed to get the ice cream to solidify.

If the ice is extremely cold to start with, there won't be any non-frozen solution like that at the ice temperature, but heat will flow from the water to the ice and melt it, assuming it doesn't freeze in the process.

You can also squeeze on ice very very hard, which lowers its melting point, perhaps below the ambient temperature. This happens under the blades of ice skates -- a very thin layer of water forms under the blades and lubricates the sliding of the blade on the ice.

In each case, thermal energy (heat) needs to be added to the ice in order to melt it, even if that heat is added from cold surroundings. It takes 80 calories per gram of energy to melt ice.

Mike W. (and Tom J.)

(published on 10/22/2007)

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