Hmmm, can't remember where I read it now. The explanation that I read for hot water freezing faster had to do with the crystalline nature in which water molecules align themselves.
Apparantly water is a very highly structured liquid if left to sit. When it's cool, (and sitting still) it apparantly conducts heat much more readily through its structure. When the water starts off hot, the exited molecules break down the crystalline structure of the water, which takes a long time to re-establish.
So basically what is meant to happen is that the initially cool water freezes throughout, meaning that the entire mass of the water has to be brought to the freezing point. In the initially hot-water scenario, the outer edges freeze more quickly.
Seemed a little wishy-washy to me though.
I remember playing with my TEC water-chiller, attempting to freeze up a few litres of water in a bucket. The water would keep on flowing down to around -2.5C or so, until the water froze up solid inside the TEC chiller, forcing the flow to stop.
I would then see some little ice crystals exit from the loop outlet into the reservoir just as the flow was stopping, and then the water turned into what can be best described as a set of icy sheet layers, of a highly crystalline nature. The whole reservoir of water froze up into this sloughy set of ice sheets, and somewhat more curiously, when this process happened, the water temperature jumped up to -0.1C almost instantly.
It was like the kinetic motion of the liquid was enough to stave off the phase-change into solid form for a while, until when the motion was removed by the flow being blocked, then that catalysed the near total phase-change of all the water in the bucket into icy sheets. Now when I say "sheets", these are not layered horizontally. They were more like at a 45 degree isometric angle kinda deal.
Yeah, I know, kids playing with water, but it was fascinating to watch the phase-change into a solid take place, and then to measure the temperature jump, and the form of the frozen water.
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