Q&A: Why does hot water freeze faster than cold water?

Seemed to me like a question long answered. This is my shortened answer:
Heat is a macroscopic characteristic of ‘microscopic’ events. In our case we have 2 bodies of water with different temperatures. The higher the temperature the higher the kinetic energy of the particles.

It is a fact that hot water freeze faster than cold water, and we have made this simple chart to represent this fact.
We can see that the hot water looses temperature faster than the cooler one and at one point their temperatures will be the same. Yet at that point the inertia of it’s particles kinetic movement would would be higher than the initially cooler water mass and because of that the hotter water will continue to loose temperature faster. This is the critical factor that determines the fact that the hot water body freeze faster. We refer here to thermal conduction witch is the principal (quantitative) means of heat transfer in the case of water bodies. We can easily see that radiation, net mass transfer, only have a very small impact on the water heat transfer while viscosity (booth bodies have the same viscosity) and chemical disipation and not specific to  the present question.
So the final answer is: Because of the intertia of the kinetic movement of particles.
This is my response to the http://hermes2012.org/ question.
You believe this is wrong ? Thanks for leaving a comment.

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One Response to “Q&A: Why does hot water freeze faster than cold water?”

  1. rod Says:
    April 15th, 2013 at 3:47 pm  (Quote)

    Hi Dan,

    I like it that you think about these things, but there are a couple of comments I would like to make.

    The rate of decrease in temperature of the water is proportional to the difference between the water temperature and the ambient temperature, which in this case must be below zero degrees C, lets say -10″C.

    It is true that the hotter water initially gets colder faster than the cooler water because the temperature difference between the water and the environment is greater. But as the temperature of the hotter water reduces and gets closer to the colder water the rate of decrease also reduces. Theoretically the two water temperatures will never get to be the same so the colder water must always freeze faster. This is the mystery.

    Remember that if the two water temperatures ever did get to be the same then the rate of decrease would also then be the same so at best they would freeze at the same time.

    While temperature itself is a measure of particle movement the rate of change of temperature in itself does not have inertia in the same sense that mass has inertia. The rate of change is only proportional to temperature difference and as soon as the difference is changed so does the ‘rate’ of temperature change.

    This effect does not always happen, but can happen under certain conditions and the explanations which I can’t recall are subtle and complex.

    Good on you for questioning and thinking about all sorts of things. It is much better to be unsure and open to learn than to be certain and wrong.

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