Name: ___________________

Date: ___________________

Homemade Ice-CreamUse science to create a colourful treat!

Legend has it that the Roman emperor, Nero, is credited as the first person to make ice cream. Nero commanded slaves to bring snow down from the mountains, which was then used to freeze the flavoured cream mixture. The scientific secret is salt! Here’s the scientific recipe that you can use at home to make your own ice-cream!

Materials

Large plastic container or jar 2 quarter-size zip-lock bags 1/2 cup of Half Cream Ice cubes Salt Flavouring (e.g. jam, vanilla essence and sugar, etc.) Towel (or winter gloves)

Method

1. Fill the plastic container about half full with ice.

2. Add about 6 tablespoons of salt to the ice. Seal the plastic container and shake the ice and salt for about five minutes.

3. Use one quart-size zipper-lock bag to mix the following ingredients: o 1/2 cup of Half & Halfo Your favourite flavouring ingredients

4. Seal tightly, allowing as little air to remain in the bag as possible. Too much air left inside may force the bag open during shaking.

5. Place this bag inside the other quart-size bag, again leaving as little air inside as possible and sealing well. By double-bagging, the risk of salt and ice leaking into the ice cream is minimized.

6. Place the bag of milk mixture inside the jar of ice. Wrap the jar in the towel or put your gloves on. Shake, rock, roll, and mix that jar! Your ice cream should be ready after about 15-20 minutes.

7. Once mixed, remove the bag of milk mixture from the jar and rinse them well with water. You don’t want any salt water accidentally getting into your ice cream.

8. Enjoy your laboratory-made dessert!

HOW IT WORKS

The freezing point is the temperature at which a given liquid turns solid. The melting point is the temperature at which a given solid turns liquid.

The freezing point of water and the melting point of ice is 0° C. When you add salt to ice, a chemical reaction causes the melting point of ice to go down and the ice becomes colder than it was before, cold enough to freeze the milk. Therefore, more energy (heat) has to be absorbed from the environment to melt the ice. Heat is absorbed from the bag of milk, which freezes the milk to make ice-cream!

DIAGRAM

1. What happens to the freezing (melting) point of ice (water) when salt is added? What happens to the temperature?

2. What happens to the milk mixture in the bag? How does this happen?

Freezing point of wate/melting point of ice.

Salt

Zip-locked bagMilk mixture

Ice-cube

Plastic container