It’s summertime and the weather is finally getting hot. Do your kids need a treat? Do you need an activity to keep them busy? Do you want them to learn about the science behind ice cream? Here is a simple science experiment that will produce a tasty treat.
Materials:
- 2 tablespoons sugar
- 1 cup half-and-half
- ½ teaspoon vanilla extract
- ½ cup ice cream salt
- Ice cubes
- 1 quart-sized Ziploc bag
- 1 gallon-sized Ziploc bag
- Winter gloves
Directions:
- Mix the half-and-half, vanilla and sugar in the pint sized bag and seal it tightly
- Fill the gallon bag halfway with ice cubes and the salt
- Put the small bag into the larger bag and seal the outer bag
- While wearing gloves, take turns with the kids shaking the bags for 5 minutes or until the mixture inside has turned to ice cream. (The bag gets super cold, do not touch the ice directly)
- Remove inner bag and wash off the salty water from the opening (you don’t want to get the brine into the ice cream… it ruins the delicious effect)
- Serve and enjoy!
The Science Behind the Experiment:
In order for ice cream to have its texture, it needs to be extremely cold. Colder than what ice normally is. Explaining why salt gets ice to drop below zero is a tricky thing, even for much older kids. Ice is a solid form of water where certain bonds happen (called hydrogen bonds). In order for the ice to melt, it needs to break those bonds, and that takes energy/heat. That’s why ice feels cold; it is drawing heat away from your hand to melt it. When you add salt to the mix, it is basically adding more stuff to pull apart after it dissolves in the water. It needs more energy to do this, and thus gets colder. Whew!
Can you clue your kids into that? If not, don’t worry. They’ll be more interested in eating the tasty concoction they made. The scientist inside of them will then want to experiment in a bit. And not just with other flavors besides vanilla.
To have them see how cold the ice can get (without touching it, of course… it is really cold), put some ice into an empty food can. On a humid summer day, water droplets will condense on the outside of the can. Get another can with ice in it and stir in a handful of ice cream salt. The can will get so cold that it skips the condensation and immediately a thin frost will form around it.
Remember, you don’t have to be a scientist to do science. There are easy ways to experiment with things right in your own kitchen, this is just one way to show you how.
Steve Davala is a middle school science teacher who likes to write. He also tries to think of things he can do to keep the minds of his own children active.
