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?
The origin of the observation goes back several years. Before the development of the "frost-free" freezer and ice makers, the most common method of making ice cubes was to fill an aluminium ice cube tray with water and place it in the freezer compartment. The ice cube tray was an aluminum tray equiped with an internal lever-operated grid to form the individual cubes and provide a means of extracting them from the tray after the water was frozen.
If warm water was placed in the tray, it would melt the layer of frost or ice that had built up on the metal ice tray shelf. This would bring the tray into close contact with the self and result in rapid heat transfer by conduction from metal shelf to tray.
If cold water was placed in the tray, the frost/ice layer would remain intact and would act as an insulator for heat transfer by conduction, leaving the heat transfer required for freezing to convection and to a lesser extent to radiation.
Note that once the "hot" water had cooled to the same temperature as the "cold" water, heat transfer by convection and radiation would be equal, but the heat transfer by conduction would remain higher for the "hot" water because the insulating frost had been melted.
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