Gardenclaw said:
Funny story: I do liquid nitrogen demos for high schools, and my professor once told me a delightful story about an older colleague of his. Now, liquid nitrogen is very cold (-300 Fahrenheit), but you can handle it for very very short periods as long as you keep it moving. (If you let it sit for too long on skin, it causes blisters and can very severely damage your skin). If you are very brave or foolish, you can put it in your mouth and breathe smoke. (If it touches your teeth, the temperature differential can make them shatter.) Apparently this older gentleman was showing some elementary schoolers that he could breathe smoke when he accidentally swallowed the liquid. Now, this didn't cause any harm (the stomach is pretty warm and pretty insulated)... until it began evaporating. Materials expand about 300 times when moving from liquid to gas, and all that gas had to go somewhere. This gentleman was apparently comically flatulent for about five minutes.
The kids loved it, apparently.