30 November 2009 South Pole Ice Cream!

I must give a shout out to Mrs. Ratliff's classes in South Carolina - they have been awesome at giving me ideas for experiments. They suggested the beard experiment (the south pole portion of which is 9 days in so far!) and also making ice cream, including the recipe and procedures! They also sent a school flag nicely decorated and signed, to get a photo at the Pole - I'll send that in e-mail when I get a good chance!

Here is a video I put together of the experience! enjoy, and try it out for yourself, it's surprisingly easy (and, unsurprisingly, a bit messy).

http://

First off, as a science experiment, I must admit I didn't really follow the rules too closely. In a scientific experiment you'd like to only change one thing (independent variable) and see how another thing (dependent variable) is affected. But in this experiment, there were many variables that changed, mostly due to availability of resources down here at the earth's bottom.

• Temperature, obviously, and altitude were different.

• Ingredients were slightly different (powdered milk instead of half-n-half). Instead of ice cubes, I used snow.

• And I did not use rock salt at all. In the classroom, the rock salt is necessary to lower the temp of the ice/water to below 32°F so the milk mixture can freeze. But at the Pole, with temperatures 60°F lower, I figured I didn't need that crutch.

So how to explain the surprising results? Which of these variables is the culprit? Talk to your science teacher about some ideas, and maybe even convince them to try it in your classroom! This is, after all, science - and you can't have science without experiments!

But here are my thoughts: In the classroom, the ice and salt mixture quickly turned into a watery icy soup. Water is a good conductor of heat, and so the warmth of the cream mixture could easily transfer into the water and then melting the ice.

Snow, on the other hand, is crystals of ice with lots of air trapped in between. The air is a great insulator of heat, and so prevents the easy transfer of heat from the cream mix into the ice. The temperature being so low, the snow never had a chance to melt and turn into water, and so this slowed down the cooling of the cream mixture, making it take longer to freeze.

Does this mean, it's too cold at the South Pole to make ice cream? Certainly not! It's just that the method we chose for the classroom (ice + rock salt) is very good in "temperate" conditions and the method I chose at the pole (just snow) is not as good. Perhaps I will try again if I can find a source of rock salt down here!