Ice cream in a can, teaching science

This summer, our hill at the lake will be used in yet another ingenious way: to make ice cream for our root beer floats. I was tempted to buy the traditional ice cream maker, but there are so many choices; I quickly became overwhelmed looking at all the bells and whistles. And besides, I have all that boy power just dying to get put to use. Plus, the process of making ice cream by hand… literally…. in the can… is is a great way to introduce some lessons in science. There is the ice cream in a bag method; my boys would surely break the bag in the mixing process. So, I’ve decided to go with the ice cream in a can method.

1. The first challenge is finding the can. Many recipes suggest using a coffee can, but who buys coffee in a can anymore? A better idea is to ask for an empty paint can from the paint store. You’ll need two: A quart, and a gallon.
2. Ask your kids to tell you the freezing point of water — or teach them — 32 degrees F, or 0 Celcius. Then, ask them what happens when we put salt on icy sidewalks. Ask them to start thinking about why we need salt to make ice cream.
3. In the small, clean can, add one cup of milk or half and half, one cup of sugar, and one teaspoon of vanilla.
4. Optional: add one tablespoon of chocolate syrup — or frozen strawberries.
5. Use a hammer to seal the lid tightly.
6. In the larger can, combine the ice and rock salt. Use a thermometer to record the temperature of the rock and salt mixture.
7. Use hammer again to seal the lid tightly.
8. Take turns rolling the can down the hill, for about five minutes. This will “solidify” the ice cream.
9. Explain what’s happening: the ice melts and combines with the salt. This “brine” has a lower freezing point — lower than 32 degrees.
10. After five minutes of rolling, open the large can, and take the temperature of the ice. It will be colder than it was the first time.
11. Open the smaller can. The colder brine was able to get the milk mixture cold enough to freeze to a solid, to create ice cream.
12. You know you’re going to have to whip up another batch right now; the fun was really rolling the can down the hill.
13. An instant way to eliminate the ice cream headache is to put your tongue on the roof of your mouth. Teaching a toddler how to do this is something you won’t soon forget.

Pictures to come…
Thursday Thirteen