If you are looking for a cool party favor at your kids next birthday, check out the 'Dragon Trick' displayed by Simon Field, who wrote 'The Chemistry of Household Ingredients.'

The trick is completely safe, painless and involves whipped cream frozen with liquid Nitrogen.

I won't pretend to understand the science behind it, but Fields did a great job of explaining it in the YouTube comments.

Actually, the fog is not the nitrogen, but the water vapor from your breath. It is the same as breathing outside on a cold day. The whipped cream has so little heat capacity that it must be popped into the mouth quickly, or it won't be cold enough to get the effect. In the mouth, it can't cool your tongue fast enough to freeze the water there. Drinking hot cocoa is more likely to hurt than this.

As soon as I can convince my kids that this is completely safe, you can bet your last dollar that we will have a bunch of 7 year old dragons at my house!