Saturday, May 5, 2007

Liquid nitrogen ice cream

As a special treat for my General Chemistry students who had to put up with me 5 days a week plus a weekly lab for a full school year, I made liquid nitrogen ice cream for them on Friday.

I love doing this demo because it tastes so good.

Here is my recipe:

2 cups half and half
2 cups heavy whipping cream
1 cup sugar
a healthy splash of vanilla

The ingredients are mixed in a plastic bowl with a wooden spoon. Liquid nitrogen is added in small amounts until the entire mixture assumes a butter-like consistence. I serve it in 3 oz cups.

It tastes great and is loaded with fat. The creams are not light by any means. I've also made a chocolate version, but that is just too rich.

There is also the visually appealing part of making the ice cream.

Students ask a lot of questions about liquid nitrogen. Like: "where can I buy it?" and "does it hurt if it touches you?"

I like to tell the story of when I was reinstalling a cold trap full of liquid N2 on a schlenk line cold finger. Some liquid N2 boiled over and landed in the palm of my hand, I had the choice of dropping the dewar flask or sucking up the pain and finish tightening the clamp. I chose the later and ended up with a nice spot of frost bite on my palm.


Matt Jenks said...

Did you synthesize your own methyl vanillate?

That is pretty cool. My high school teacher always did all sorts of really cool demonstrations, and I blame her on helping turn me into what I am today (not the overweight and bearded would-be author part, either).

The coolest was when she taught how to make a battery out of a lemon, a penny and a nickel. I love any practical demonstration that ends in "and then you lick it"

Greg the Chemist said...

I really should try this some time.