ELi5: How is liquid nitrogen super cold and in the form of liquid when the container itself is in a room temperature environment?

Question

ELi5: How is liquid nitrogen super cold and in the form of liquid when the container itself is in a room temperature environment?

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Answer 1

The container is a really efficient thermos. Its hollow walls are evacuated, which insulates the contents from ambient heat. It isn’t perfectly insulated though l, and so the liquid nitrogen eventually evapourates away.

Essentially, once liquid nitrogen exists, it must be actively rechilled or it is just a matter of time before it evapourates.

BTW, to make liquid nitrogen you compress gaseous nitrogen, refrigerate the compressed gas, then rapidly decompress the gas. Expansion cooling disperses enough energy to cause the gas to condense into a liquid.