Many Years Ago I Watched A Program Filmed I Believe In Finland,

it was filmed in winter, 

the presenter took a mug of boiling water, threw the water into the air where it froze immediately, the point was that if you did the same thing with cold water it would not freeze, this phenomena is known as the Mpemba effect, Aristotle first noticed that hot water freezes faster than cold water but chemists have always struggled to explain the paradox, until now, Xi Zhang at the Nanyang Technological University in Singapore says that the Mpemba paradox is the result of the unique properties of the different bonds that hold water together,

so what’s so odd about the bonds in water? a single water molecule consists of a relatively large oxygen atom joined to two smaller hydrogen atoms by standard covalent bonds, but put water molecules together and hydrogen bonds also begin to play an important role, these occur when a hydrogen in one molecule comes close the oxygen in another and bonds to it, chemists have long known that they are important, 

for example, water’s boiling point is much higher than other liquids of similar molecules because hydrogen bonds hold it together, but in recent years, chemists have become increasingly aware of more subtle roles that hydrogen bonds can play, for example, water molecules inside narrow capillaries form into chains held together by hydrogen bonds, this plays an important role in trees and plants where water evaporation across a leaf membrane effectively pulls a chain of water molecules up from the roots, so now I know why boiling hot water freezes faster than cold water, (I think).