Why does cold water freeze faster then warm water?

Generally colder water will freeze faster. If you put both hot and cold water into a freezer, the hot water first has to get cold, so the cold water has a head start towards freezing....but let's look at some factors that might change the issue for particular situations-- 1) Hot water could melt accumulated ice in the freezer, resulting in defrosting of the walls and perhaps better efficiency. 2) Hot and cold water might be slightly different in dissolved minerals, so they may not have the same freezing point. 3) If you put both into a freezer right next to each other, the two pans might have to equilibrate (get to the same temperature by sharing the heat). Any object will lose heat at a set rate governed by the temperature differential : the bigger the difference in temperature the more heat is dissipated. In the case of water the hot water does lose more heat to the surrounding air but as the difference between the two closes so does the rate of heat loss. therefore if a cup of boiling water cooled to 50 degrees in 1 minute another cup of water at 50 degrees may have only cooled to 30 degrees. Please note that the numbers here are purely for example purposes. Footnote: If you take water that has been boiled and allowed to cool to room temperature, it will freeze faster than an equal quantity of tapwater brought to room temperature without boiling.