Question: through which process do you liquify the oxygen

Kathryn Boast answered on 4 Mar 2019:

OK, here goes! Liquid nitrogen is dangerous though – so don’t just try this for yourself!
KIT:
⭐ Liquid nitrogen (which is very cold: -196C!)
⭐ An empty coke can
⭐ A clamp stand
⭐ A small dewar (like a tiny thermos flask)
METHOD:
⭐ Clamp the coke can in the stand so that it is diagonal
⭐ Put the dewar underneath the bottom of the coke can
⭐ Pour liquid nitrogen into the coke can so it is about 1/3 full
⭐ Oxygen that is in the air will condense on the outside of the can, and because you have it held diagonally, it will run down to the bottom of the can and drip into the dewar. This works because oxygen has a slightly higher boiling point than nitrogen (so it goes from being a gas to a liquid at a slightly warmer temperature). If you run it long enough, you can collect about 30ml of liquid oxygen in the dewar. This doesn’t sound like much, but liquid oxygen is really dangerous (it can make things burn without a match or anything) so we don’t really want too much of it!