Our spring-like weather prompted me to plan a fun science experiment. James and Steven needed a break from studying Avogadro's number, molar mass, atoms, etc.
They made ice-cream in a bag.
Of course they also learned the science behind it.
The salt melts the ice by breaking apart the hydrogen bonds that form its hexagonal crystal lattice structure. Melting is an endothermic process (energy is absorbed from the surroundings.) The surroundings are comprised of the ice cream mixture in the bag. As energy is removed from this mixture, it will freeze into ice cream.
To make ice cream, it's necessary to have the temperature lower than the normal freezing point of water, because addition of sugar, vanilla, and other substances used in making ice cream depress the freezing point of water. Adding salt to the ice lowers the temperature that water freezes in.
Did you know that kneading is important to the process, since this introduces air into the mixture, giving ice cream its distinctive taste and flavor?
Ice Cream in a Bag
gallon freezer bag
two quart freezer bag
rock salt
crushed ice
1/2 cup milk
1/4 cup evaporated milk
4 tsp sugar
1/2 tsp vanilla
- In the quart freezer bag, place the milk, evaporated milk, sugar and vanilla. Seal the bag
- In the gallon bag, fill halfway with ice. Add 1 cup rock salt.
- Place the quart bag in the gallon bag and seal the gallon bag. Knead with your hands for about 20 minutes. After this time, remove the small bag and enjoy a delicious treat!
*Note: The bag gets really cold. The kids ended up putting gloves on when kneading the mixture.
