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| In violation of Thermodynamics (Posted on 2003-05-11) |
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Many have heard the "old wives tale" stating that if you put hot water into a freezer, it freezes in less time than it would have if it had been cold to start. Never did I believe such a claim, as it runs contrary to one of the basic laws of nature.
While surfing one day on sites illustrating "bad science" I actually found a plausible real life reason why this in fact can be true (read:not always true, but possible). Running this experiment under controlled conditions [eg. measure the same volumes of hot and cold water, make sure containers are equal in any relevant aspect (shape, material, conductance properties, covered or not etc.), and that the freezer is properly set to achieve a uniform temperature throughout], can you come up with a reasonable set of conditions for which the water in the hot container would freeze before the water in the cold container?
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Submitted by Cory Taylor
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Rating: 3.1429 (7 votes)
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Solution:
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The situation relies on two conditions being fulfilled; first that the hot water is near the boiling point of water, such that significantly more of the original volume of hot water will evaporate than the cold, leaving a smaller volume of water to freeze, while the temperature of the cold water is high enough to prevent fast freezing (i.e. the "cold" water would have to be fairly warm), and second, the initial volumes of water would have to be fairly small, so that the volume loss to evaporation would be significant. This could produce a situation where the hot water in fact froze faster than the cold water in.
Of course this neglects that much of the hot water, which has evaporated, in fact would freeze after the cold (vapour) freezes, but (for solution purposes)because it is no longer contained in the jar it doesn't count.
Note: I have NOT tested this (as I don't own all the necessary sensitive chemistry equipment), but it seems plausible enough, given just the right circumstances.
This is not an original problem, but I can't credit it due to a poor memory. |
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