Stand Back, I’m Going to Try Science!
My father is a chemical engineer at a large company. He volunteers in an outreach program where the company gives him science demonstrations aimed at precocious elementary schoolers, and he periodically goes to schools and birthday parties and stuff to show how neat science is. One of the kits he does is all about cryogenics, where he gets about a gallon of liquid nitrogen (LN2), and demonstrates what happens to things when you freeze them really cold. He talks about how matter can be a gas, a liquid, or a solid, and how its properties change as it goes from one state to another and changes temperature (racquetballs become brittle, flowers become crumbly, small amounts of LN2 boil into large amounts of nitrogen gas, etc).
He did a demonstration a couple days ago, and still had some LN2 left over from it. Ordinarily he just pours the rest out on the street (it boils away quickly, and no one notices since air is already about 78% nitrogen). However, this time we convinced him to keep it around for a few days so we can try freezing other things. Some stuff about LN2, and some safety tips, followed by a bunch of pictures →