Fun With Liquid Nitrogen


This morning I volunteered at “Super Saturday,” a college event where UNCA students and faculty teach a series of Saturday morning classes for academically gifted area gradeschool kids in 3rd-8th grade. There are all kinds of cool classes offered — math, acting, cartooning, calligraphy, chess, chemistry… As a chemistry major, I volunteered with the chemistry department for the “Chemistry Matters” class.

It started out very lamely. I remember thinking if I was a parent, I’d have wanted my money back. The young student teaching was just a total teenaged goofball, unprepared, sending people back to his apartment to get what he didn’t bring, no gift for explanation or creating drama or interest… I resigned myself to a dull morning.

And then the magic happened. We brought out the liquid nitrogen. As my friend Sherman said to me when I bumped into him after the class, “It ain’t a party until you bring the liquid nitrogen out.” That shit is amazing. If I sold it, I would call my brand Liquid Cool.

Liquid nitrogen is so cold that it boils at well below room temperature. Dip something into it, even in its boiling state, and whatever you dunk will soon freeze solid, as the temperature of liquid nitrogen is 320 degrees below zero. Very, very cold.

You can’t get liquid nitrogen just anywhere. You have to have a license or something. So if you are a college student and your university’s got a license, and you’ve got all the liquid nitro you can mess around with in an hour, you are in for good times. Especially when you throw in 16 crazy little brainy preteen kids. Liquid nitrogen, BTW, is not an expensive substance. At about a buck for a glassful, it’s as cheap as soda. So we could fucking go for it. And we did.

First we poured it all over the place. On the table, on the floor… The nitrogen pours out of the canister just like water would, and it looks like water, but has a strange smoky, cloudy translucence. It steams and boils when it hits the air, and if you pour it it makes roiling waves of smoky white cloud on the floor. If you’ve ever seen special-effects fog from a dry-ice fog machine, it looks like that. Little bits of nitrogen ice spray out from where the liquid hits the floor, skittering away and sublimating (the fancy science word for what happens when a solid goes straight to a gaseous stage without ever really melting).

It doesn’t wet anything in our everyday world to pour liquid nitrogen on it. Everything in our everyday world is so much hotter than the liquid nitrogen that the liquid nitrogen boils away on contact. Pouring liquid nitrogen onto something only makes it turn cold, not wet. When you pour liquid nitrogen onto a tabletop, there is no wet spot. Only a dry spot of freezing cold.

Dr. Heard, UNCA’s jolly Australian chemistry prof (pretty much just along for the ride, with some of his students in charge of the class), did his shtick, which is to pretend to drink liquid nitrogen. Now obviously he wasn’t really drinking it, but he raised the insulated canister to his lips, tipped it back, and then lowered it, smacking his lips with satisfaction as big curls of white steam puffed out of his mouth (I feel certain that the trick here is to just inhale the steam as you pretend to drink). Great stuff!

And then we made liquid nitrogen ice cream. It’s the easiest ice cream recipe of all. Just mix your ingredients (cream, sugar, flavorings — we made cinnamon ice cream) and then pour in a few big splashes of liquid nitrogen and stir well! It seems like eating ice cream made with liquid nitrogen would kill you unless you were from the ice-planet of Zorg, but it doesn’t. In fact it was quite tasty. The cold liquid nitrogen just freezes the cream and boils harmlessly away (colorless, odorless nitrogen, hardly a poisonous gas, is in your lungs right now and comprises about 80% of Earth’s atmosphere). After a few minutes of stirring, your bowl of cream and sugar is now marvelously smooth and rich instant homemade ice cream. Damn!

We also froze an onion and busted it on the floor. Science! To do this, you submerge your onion in a big beaker of liquid nitrogen until it freezes solid. This looks really cool, as the onion — much hotter than the freezing nitrogen — makes the liquid in the beaker immediately come to a hard rolling boil. It looks for all the world like a beaker of boiling water, but there’s no heat source under it. It never ceases to delight me to be reminded that water’s boiling point is not the only boiling point in town. Liquid nitrogen begins to boil at 78 degrees above absolute zero. At room temperature, it smokes and steams and bubbles like a witch’s cauldron. Plop an onion in a beaker full and you get an instantaneous hard boil. The nitrogen is freezing cold, cold enough to freeze your finger solid if you held it in there, but boiling away into gas.

So what happens when you freeze an onion that way? And then awesomely hurl it into the linoleum floor of the chemistry department hallway? It (the onion) doesn’t quite shatter like glass, sad to say. Ours had only frozen to a hard and clunky lump of oniony ice, like an old snowball left out overnight. A second throw got it to shatter into a hundred chunks, which soon unfroze and made the hallway smell like a dirty armpit. Guess what volunteer got to clean that up?

A second onion was allowed to “boil” a little longer. The student teacher meant business this time, and threw it hard at the floor, where it broke into proper onion-shards with a tinkling smashing sound.

The kids loved it. I don’t know how much science they learned (quite possibly a fair amount), but they had a cool experience with an unusual substance, got to see a college chemistry lab, and ate alien ice cream frozen by the magic of chemistry. If I was a kid, I’d never forget it. I’m 37 and I still had a great time.

(And I looked, as I always look, at how many boys and how many girls there were in the class. Eight of each, split right down the middle. Just as it should be.)

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