Ice Cream in a Bag

I learned this trick in school from one of my favorite science teachers and have used it since then. It is very simple to make and is a fun activity for children and adults alike. This can also be a healthier alternative to store bought ice cream.

Ingredients:

1 cup Milk

2 tbsp sugar

1 tsp vanilla extract

toppings(optional)

4 cups ice

about 1/3 cup rock salt

Equipment:

gallon size plastic bag

quart size plastic bag

work gloves(optional)

This step requires the milk, sugar, vanilla extract, and quart size plastic bag.

Combine the milk, sugar, and vanilla extract in the quart sized plastic bag. Before sealing, try to squeeze excess air out of the bag to prevent a rupture. Be sure to seal the bag tightly!

*Tip: Add the toppings after the ice cream is frozen- this lets the ice cream freeze faster because a less amount of items is being frozen

This step requires the gallon size plastic bag, rock salt , ice, and ice cream mixture bag

Fill the gallon bag with the ice and rock salt. Next add the ice cream mixture bag to the gallon sized one. Now we are ready to start the freezing process!

*Note: if coarse rock salt is unavailable, other types like pink coarse salt may be substituted. In the case where the size of the salt is significantly smaller than normal coarse rock salt, a slightly larger amount of salt can be added.

This is the fun part: shaking!

In my experience, it takes about five minutes for the ice cream to freeze. All that is needed to be done is to shake the bag from side to side. (See above)

*Tip: Occasionally poke at the inner bag through the large one to feel the hardness of the ice cream - more shaking means colder and harder ice cream .

*Note: This is where the gloves come in. Although optional, the gloves are a helpful insulator between the hands and the cold bag.

After about five minutes, you should have delicious, creamy ice cream!

*Important: Make sure to check for rock salt crystals before opening the bag because biting into one would NOT be a fun treat!

The main principal working in the bag is called freezing point depression. In terms of this project, the melting point of the ice is lowered by the salt. When the ice and salt combine, the ice has a lower melting point that makes the ice colder and allows the dairy mixture to freeze into the delicious treat that we call ice cream. -M.S.