Hot water freezes faster than cold - and now we know why.

See the link below for the technical details, involving stretching of bonds between between the atoms in the water molecules.

http://www.iflscience.com/chemistry/hot-water-freezes-faster-cold-and-now-we-know-why

November 1, 2013 | by Tamsin E Laird

Hot water seems to freeze faster than cold water, known as the Mpemba effect. The effect was named after the Tanzanian student who in 1963 noticed that hot ice cream mix freezes faster than a cold one. The effect was first observed by Aristotle in the 4th century BC, then later Francis Bacon and René Descartes. Mpemba published a paper on his findings in 1969. - See more at: http://www.iflscience.com/chemistry/hot-water-freezes-faster-cold-and-now-we-know-why#sthash.Xs6d1BMr.dpuf

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Now a team of physicists from the Nanyang Technological University in Singapore, led by Xi Zhang, have found evidence that it is the chemical bonds that hold water together that provide the effect.

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