Why Do You Need Salt to Make Ice Cream?

Salt melts ice and gradually cools the ice cream mixture.

In order for ice cream to have a smooth and creamy texture, it must freeze quickly and evenly. This is done by cooling the mixture with ice and salt. It's a simple chemical process that helps create a delicious treat.

Properties of Water

Water freezes when its temperature reaches 32 degrees Fahrenheit. If you put an ice cube in water, some of the ice will be melting and some of the water will be freezing because the ice is lowering the temperature of the water. As a result, either the water will freeze or the ice cube will melt, depending on which process happens faster.

Lowering Freezing Point

When salt is added to water, it lowers the freezing point of water. Salty water will freeze at temperature lower than 32 degrees Fahrenheit. This is why salt is used to melt ice on roads because ice will not form there unless the temperature drops further. If the concentration of salt is high, the freezing point will be much lower.

Making Ice Cream

Ice cream freezes at temperatures lower than 32 degrees Fahrenheit. Placing the mixture into a freezer will not do the trick. To have a smooth texture, ice cream needs to cool down gradually. To make ice cream, mix milk, sugar and vanilla in a zip-top bag and put it in a larger zip-top bag that contains ice and salt. Salt will melt ice as it gradually absorbs the heat from the ice cream mixture. As its melting, it will cool the ice cream. Rolling and shaking the contents of the bags will ensure that ice cream cools down and freezes evenly.

References

• Worsley School: Salt and the Freezing Point of Water