Science for the simple mind (me To lower the temperature of 1gm. of water 1degree C.we need to extract 1 calorie of heat energy from the gm of water. So to reduce the temp.of 1gm of water by 80 deg C we extract 80 cal. so the temp. of the gm. of water at 80 degC falls to 0 deg C. To freeze the gm of water ,now at 0deg .C we need to extract the 'Latent heat of fusion' at 80 cal. per gm. So we need to extract the same amount of heat (80 cal.)from the gm.at 0deg.C to freeze it as we did to cool it from 80 -0. So we take hot water from the hot tap at 80C!! and cold from the cold tap at 10C and stick the 2 equal samples outside at -5C. The hot sample loses heat more quickly than the cold sample so the time to reach 0deg C is less than might be expected but still more than for the cold sample but both timesare 'dwarfed' by the time needed to extract the 'Latent heat' at a small temperature differential.So put simply hot water freezes less quickly than cold but the difference is nowhere near as great as 'one' might expect.
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