Question: What would happen if you pour liquid nitrogen into a furnance

Steven Thomson answered on 14 Jun 2015:

I like questions like this!

It depends how much liquid nitrogen you pour in, and how fast you pour. Liquid nitrogen boils at -196C, and a furnace will be at least several hundred degrees about zero.

The first thing that will happen is the the liquid nitrogen will boil! When you pour in the super-cold liquid, the furnace will heat it up above -its boiling point very quickly, turning the liquid nitrogen back into gas. But to do this, the furnace has to give some of its heat to the nitrogen, so the furnace gets a tiny bit colder.

If you had enough liquid nitrogen, you’d eventually freeze the furnace. But there’s a problem – when nitrogen boils, it expands. Nitrogen in its gas form takes up roughly 600x more volume than liquid nitrogen. This means that if you pour liquid nitrogen into the furnace, it’ll boil, turn into a huge amount of nitrogen gas and would push all of the oxygen out of the room.

So if you wanted to pour enough liquid nitrogen into a furnace to freeze it, you’d need to be wearing an oxygen tank like a scuba diver, or else you’d suffocate from breathing almost pure nitrogen!