Question: How come liquid nitrogen doesn't freeze everything it touches

Thomas Barrett answered on 11 Mar 2015:

So if you spill liquid nitrogen on something the thing it is spilt on (your hand or the desk) is rather warm. Your liquid nitrogen gets warmed up by touching the object and the contact between the two actually boils the liquid nitrogen (it has a really low boiling point) and this causes a cushion to form between the layers and stops if from freezing it.

Liquid nitrogen also evaporates really quickly so a small spill wont have time to lower the temperature of what it touches to freezing before it is all gone. Thats how you can spill it onto yourself (don’t try it at home) and it be ok if it is a small amount. Larger spills take longer to disappear so they can begin lowering the temperature enough to remove the cushion between nitrogen and the object and cool it to freezing. So big spill so liquid nitrogen are dangerous, small ones aren’t.