How To Teach Science During Dessert… With Ice Cream
With the hot weather coming our way, I would guess that many of you are going to need some refreshing desserts to cool you down. This week, not only are you going to learn the science behind ice cream, you are going to learn how to MAKE ice cream! Let’s get to the good part first…
Here’s what you need:
½ cup whole milk ½ cup half and half ¼ cup sugar ¼ tsp vanilla One gallon-sized and quart-sized sealable baggie 2 cups of ice ½ – ¾ cup of rock saltHere’s what you do:
Pour all of the ingredients except for the ice and salt into the quart-sized baggie. Seal it up and mix well!
Place the ice and rock salt into the gallon-sized baggie.
Now place the sealed baggie with your cream mixture into the larger baggie and seal it up.
Shake the bag from side to side for about 10 minutes. You may want to cover the bag in a towel if your hands get too cold.
Open the gallon bag to remove the smaller baggie when the blended mixture has solidified into ice cream.
What’s going on?
The four main concepts of science are easy to observe while making ice cream:
The ATOMS that are found within the liquid milk have a lot of energy as they move around freely and bounce into each other and the side of the baggie. It is very easy to DIFFUSE energy from a warmer liquid (like milk) into the ice within the baggie. Remember, DIFFUSION is the movement of atoms (or energy) from high concentrations into low concentrations.
Ice has to absorb energy in order to melt. When you use ice to cool the ingredients for ice cream, the energy is absorbed from the ingredients and from the outside environment (like your hands!)
When you add salt to the ice, it lowers the freezing point of the ice, so even more energy has to be absorbed from the environment in order for the ice to melt. This makes the ice colder than it was when you put it in the baggie!
This super cooled ice DIFFUSES more and more heat energy from the liquid milk. As the ATOMS within the milk lose energy, they slow down, line up (like soldiers in formation), and form what is known as crystals!
Many people may believe that the creation of this frozen dessert is nothing short of magic. Naturally, we already know that you have not created any new ATOMS with all that mixing of the baggie. The creation of ice cream follows the LAW OF CONSERVATION which states that ATOMS cannot be created or destroyed, only rearranged.
And you rearranged a lot of ATOMS with all that shaking!
The real question is about the DENSITY of the newly created ice cream. If you stopped shaking your mixture too early, you probably noticed that you had a pretty thick fluid that was only partially frozen. If that was the case, your “ice cream” was really just frozen water mixed with the proteins and fat (inside the milk) and the sugar you added to the baggie.
If, however, you mixed your creamy dessert very well by shaking it around a lot you may have received a much less DENSE ice cream. But how?
As you shook your baggie, you mixed in air bubbles within the freezing ice cream. These bubbles get in the way of ice crystals as they begin to freeze together. The result is a fluffier, less DENSE ice cream as the solid ice crystals get spread out a greater distance!
You want much fewer ATOMS inside a teaspoon of ice cream as compared to a teaspoon of liquid milk… SO DON’T GO EASY ON THAT BAGGIE! SHAKE IT UP!
Learn more about chemistry concepts (and many more) in the Classic Science: Series for the Family and be certain to come back every Thursday or subscribe to The Blog of Mr.Q to learn more about how to teach science during breakfast, lunch, and dinner!
