The puzzling reason of why hot water freezes faster than cold has now been figured out. The effect is known as the Mpemba effect, named after a Tanzanian student who noticed that hot ice cream mix freezes faster than a cold one, the phenomena was actually first observed by Aristotle, and then later Francis Bacon and René Descartes.

It has since puzzled scientists for long. Now, Xi Zhang and his colleagues from the Nanyang Technological University in Singapore says they've  evidence which suggests that it's the chemical bonds that hold water together which provide the strange effect.

Each molecule of water is made up of two hydrogen atoms bonded to a single atom of oxygen. The bonds, which involve atoms sharing electrons are well understood, but it is the separate water molecules that are bound together by weaker forces generated by hydrogen bonds.

This occurs when a hydrogen atom from one molecule of water sits close to an oxygen atom from another, giving rise to many of water's interesting properties.

Xi Zhang and his colleagues are suggesting that the same bonds cause the Mpemba effect. The water molecules come into close contact, and a natural repulsion happens between the molecules causing the covalent bonds to stretch and store energy, and the hydrogen bonds stretch as the water gets less dense and the molecules start moving further apart.

The process of covalent bonds giving up energy is equivalent to cooling, giving rise to the Mpemba effect where warm water cools faster than cold.

If this theory holds true, and in a large scale, one would think what would happen if the world suddenly became hotter. Will we enter another ice age? [arXiv via Medium]