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To make ice-cream we use a whole bunch of different principles from physics and chemistry. In our video, we use salt to reduce the freezing point of water to make delicious, homemade ice-cream in minutes.

Safety: When handling food, use clean hands and equipment.

Video transcript available here.

Adding salt to the ice allows the water to get to a temperature below 0°C without freezing.  This cold water around the ice-cream tin allows for good conduction of the heat out of the mixture.  The salt dissolves into any of the liquid water coating the ice and bonds with the water molecule, making it harder for the liquid to form back into an ice crystal at 0°C.  The water surrounding the can now has a much lower temperature to cool the ice-cream mixture.

If you’re think making “salty” ice-cream at home or on the road (it’s fun for camping), it should take 15-20 minutes for the mixture to freeze.

Teacher’s notes with curriculum links available here.