I scream, you scream, we all scream for ice cream – especially during National Dairy Month! It’s believed that ice cream has been around since the time of the Roman emperors. In those days, the emperor ordered slaves to bring snow down from the mountains in order to freeze the ice cream ingredients. The hand-cranked ice cream churn was invented in 1846, and ice cream cones debuted at the 1904 World’s Fair in St. Louis. Thank goodness this icy treat has lasted through the ages! Although we can easily get our own ice cream in a store or ice cream shop, it’s very easy to make your own. You don’t even need a machine – you just need a few zip-top plastic bags and some cool moves!
Homemade Ice Cream in a Bag
Have your junior ice cream makers place the ingredients in a quart-sized zip-top bag and seal it completely. If you get any kind of hole in this bag, you’ll end up with salty ice cream – not good! You can even double-bag at this point if you want to be safe. Ask the kids how ice cream begins – is it a liquid or a solid?
Add ice and 1/2 cup of rock salt to a larger freezer bag. Measure the temperature of the ice before and after the salt is added. What effect does the salt have on the ice temperature?
Place the ice cream bag inside this larger bag of ice and knead, shake and shimmy away! If you want to have a “freeze-off,” have each person make their own bag and come up with their own unique, signature ice cream mixing move. r maybe play freeze dance while your kids sing along to the Frozen soundtrack. Time the process and see whose got the “coolest” (fastest) ice cream making moves!
Why do we need salt to turn our milk into ice cream? Just like salt trucks working hard on icy roads, the rock salt mixes with the ice cubes causes the ice to melt. The salt lowers the freezing point of the ice. Do you think the amount of salt you add to the ice matters? It does! The more salt you have, the lower the temperature will be before the salt-water solution freezes. By lowering the temperature at which ice is freezes, you create an environment in which the liquid ice cream ingredients can freeze into a chilly treat.
Once the ice cream mixture begins to harden, you’re ready to enjoy your sweet creation. Before you remove the ice cream from the bag, ask the kids to predict if it will be a liquid, a solid, or something in between. Divide your ice cream equally among bowls. How many people does one bag of ice cream serve?
You can make roly-poly ice cream with coffee cans. Use a clean 1 lb coffee can with a tight-fitting lied to mix your ice cream ingredients. Duct tape the lid shut to avoid salty ice cream! Place the can in a larger, 3 lb coffee can. Fill that can with ice and rock salt. The added benefit of this method is that besides shaking, you can roll or kick the can around the yard to make your ice cream. After 10 minutes, remove the lid, stir the ice cream, replace and retape the lid. Drain any excess water and repack with ice and salt. Roll, shake or kick for another 10 minutes or so.
The next time you enjoy your favorite frozen dairy treat, be sure to tip your spoon to the math and science that make the magic happen!
Image licensed by Ingram Publishing