Ever heard that Hot water freezes faster than Cold water?
Sounds counter intuitive doesn’t it? Well it’s true. This phenomena is one of the long standing puzzles that still defy explanation. The question has been asked over the millenia and to this day there has yet to be a simple solution to the bizzarre behavoir exhibited by water.
He’s my musings that have been bugging me for quite some time with regards to this question.
After hearing out the Merlin 2012 competition created by the Royal Chemistry Society regarding this subject I have looked at this an issue of chance. Probability and form.
Simply put, water freezes faster when heated beause it reduces the contrainsts upon the water molecules imposed by the formation of Hydrogen Bonds. It is these bonds that are at the heart of the conumdrum. As stated by Wikipedia, the average number of bonds reduces in water as it is heated and increase as it cools.
With less bonds, the probability of the jostling H2O molecules are statistically more likely to bond more easily as they do not have the constraints of existing bonds, rotation etc upon them.
It’s akin to making a puzzle, you start with the outer edges and work inward. With water freezing, we see the outer surface freeze first then freeze toward the centre.
With hot water the reduced h-bonds allow the water molecules to re-orient more easily and with a greater rate due to the inherent energy in the fluid.
This is counter to cold water where the number of h-bonds is higher and with less energy the rate of interaction is slower.
So, as i said, it’s all to do with chance and form. the beauty of ICe formation is that it has rules. The molecules only form ice on the basis of angle & distance.