Liquid nitrogen
is fantastic stuff to play with.

You can dip your bare finger in it for brief periods, despite its temperature being a maximum of -195°C, because the heat from your finger is enough to instantly boil a layer of nitrogen around it, so the skin doesn't actually touch the liquid.

The skin does cool down though, and any more than a second or two in the nitrogen results in a very cold, frostbitten finger. Frostbite hurts.

*knows*

I also once made a nitrogen bomb. This was a plastic milk bottle, with a little liquid nitrogen poured in, then a bung jammed in the top. For best results it should be rolled gently across the floor. This both chills the plastic of the bottle so it becomes brittle and also, because of the heat transferred, increases the rate at which the nitrogen evaporates, so the explosion occurs more quickly.

And it's a hell of a bang!
( K2k6 has a proper job these days, Mon 6 Oct 2008, 15:05, Reply)