Chemistry
The Science of Supercooling and Nucleation in Water Freezing
Quick fact
Pure water can be cooled to about -40°C before freezing, and even -48°C in tiny droplets, because it lacks the impurities or surfaces needed to kick-start ice formation.
Why this is interesting
You've probably seen a bottle of water freeze instantly when you tap it. But why does it stay liquid in the freezer, and then turn to ice in a split second?