1. The document provides instructions for making homemade ice cream using a salt and ice mixture. 2. It explains that adding salt to ice causes the melting point of ice to decrease, making the ice colder and able to freeze the milk ingredients sealed in a plastic bag. 3. As the bag of milk is shaken in the salty ice water, the heat is absorbed from the milk, causing it to freeze into ice cream.

1. Name: ___________________
Date: ___________________
Homemade Ice-Cream
Use 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 & Half
o 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!

2. 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 bag
Milk mixture
Ice-cube
Plastic container