Ice-cream in a bag

Ice-cream in a bag

Ice-cream in a bag

Follow FizzicsEd 150 Science Experiments:

You will need:

Half a cup of milk.

Half a cup of cream.

Chocolate or strawberry topping.

A medium strong plastic freezer bags

2 Zip-loc bags.

Half a cup of salt

Crushed ice and a hand towel

A mixing bowl

A spoon

How to make ice-cream Science experiment - setup_materials
1 How to make ice-cream Science experiment - mixing milk, cream and topping

Mix the milk, cream and topping in the mixing bowl.

2 How to make ice-cream Science experiment - transfer of milk substance to zip-loc bag(2)

Pour the mixture into a Zip-loc bag.

3 How to make ice-cream Science experiment - transfer of milk substance to zip-loc bag

Squeeze the air out of the bag and seal it.

4 How to make ice-cream Science experiment - double bagging mixture

Place the bag with the mixture into another bag, and seal it again.

5 How to make ice-cream Science experiment - mixing ice and salt(1)

In the mixing bowl, mix the crushed ice and table salt.

6 How to make ice-cream Science experiment - transfer salt_ice mix into freezer bag

Place the Zip-loc bag containing the mixture into a freezer bag.

7 How to make ice-cream Science experiment - transfer salt_ice to freezer bag

Fill the freezer bag with the crushed ice and salt mixture.

8 How to make ice-cream Science experiment - mixing bag solutions

Push out the air and seal the bag.

9 How to make ice-cream Science experiment - massaging bags

Holding the bag in a hand towel, gently massage or shake the freezer bag to cool the ice cream mixture. Make sure the crushed ice surrounds the inner Zip-loc bag.

10 ice cream

After about 15 minutes your ice cream is ready to eat.

Why Does This Happen?

Water normally freezes at 0Celsius, however adding the salt causes the freezing point of the ice to be lowered. A 10% solution of salt in water lowers the freezing point of water to – 6oC, where as a 20% salt solution lowers the freezing point to – 16oC. Salt water therefore needs a lower temperature to become a solid. This means that you end up having ‘super cooled water’ touching the inner bag, which helps to freeze the ice cream inside. 

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