Chad Orzel points to a collection of amusing science “merit badges”. In particular, Chad highlights:
The “has frozen stuff just to see what happens” badge (LEVEL III).
In which the recipient has frozen something in liquid nitrogen for
the sake of scientific curiosity.
Ah, how I miss liquid nitrogen. Back in the day, we had this thing called the Physics Circus, where we’d go out to local elementary schools and give physics demonstrations to the kids. It is amazing how enthusiastic third and fourth graders can be. If you ask a bunch of fourth graders “how do you think this worked?” you get a forest of hands shooting up, and all sorts of wonderful ideas. Of course, you have to catch them at the right age, because just a couple years later, they transform into sullen middle schoolers. But right before that, kids are amazing little scientists.
Anyway, we had a boatload of demonstrations about electricity, Newtonian mechanics (the weighted bicycle wheel in the spinny chair, that sort of thing). But the one the kids really loved was the liquid demonstration. Unlike the other demonstrations, there really wasn’t much scientific content to the liquid nitrogen segment of the show. The message was basically, “freezing things with liquid nitrogen and breaking them is really cool.”
Personally, I was less interested in breaking things with liquid nitrogen and more interested in just playing with the stuff. I used to pour a few drops on my hand and watch the droplets skitter across the surface, like water droplets on a hot stove (in fact, exactly like water droplets on a hot stove). If you were careful, you could also stick your hand directly in a dewar of liquid nitrogen. One professor I knew would pour a little liquid nitrogen in his hand, slurp it up, and shoot steam out of his nostrils. I never dared try that. He had achieved a sort of Liquid Nitrogen Zen Mastery.
Of course the best of all was the liquid nitrogen ice cream. You just get the ingredients for ice cream as if you were going to make it using a traditional ice cream machine, with the rock salt and everything. But instead of turning the crank for an hour, you just pour the ingredients in a bowl, pour in the liquid nitrogen, and stir, stir, stir. Vapor pours out of the bowl like a witches cauldron, and in less than five minutes you have smooth, creamy ice cream. The bubbling during the freezing process aerates the ice cream perfectly, and it all freezes too fast to form any ice crystals. Liquid nitrogen! It is so choice. If you have the means, I highly recommend picking some up.