Liquid nitrogen has one of the lowest boiling points of any known substance at -321ºF, which is why anything that comes in contact with the substance is usually flash-frozen.
A substance’s boiling point varies with air pressure. For example, at sea level, water boils at 100ºC (212ºF). But at the top of Mt. Everest, where the air pressure is only about a third of what it is at sea level, water will boil at 71ºC (160ºF).
So as the air is sucked out of the vacuum, the liquid nitrogen’s boiling point drops below the substance’s temperature inside the vacuum, making it a superheated fluid. This superheated liquid nitrogen does some crazy things:
The evaporation of the nitrogen during boiling cools it back down until it freezes solid. In an attempt to align its molecules in a more tightly-packed pattern, all of the atoms will reorient themselves in a fraction of a second, causing cracks to spread quickly in fractal patterns across the solid nitrogen.
Liquid nitrogen isn’t just cool for science experiments. It’s widely used in every day life as a refrigerant for the freezing and transportation of food and as a coolant for superconductors. It’s even used to freeze off skin abnormalities like warts.
(h/t IFL Science)
