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Description

Making Ice Cream without a Freezer

Resources

Ice, Salt, Milk, Salt, Ice, Caster Sugar, Large & Small Zip Lock Bags, gloves

Instructions

See pdf thank you science museum


Information for Scientist Badge

How to change the experiment
1. Alter the type of salt used - does rock salt work quicker than table salt for e.g.
2. Change the proportions of salt/ice used. Can the scouts find the best proportions?

How it works
The same reason salt is used on icy roads and sidewalks in winter explains why salt is mixed with ice to make ice cream. Salt causes the ice to melt. When salt and ice mix, the freezing point of the ice is lowered and the freezing point reached depends on the amount of salt used. The more salt is added, the lower the temperature can get before the saltwater solution freezes. For example, water will normally freeze at 32℉ (0℃). A 10% salt solution freezes at 20℉ (-7℃) and a 20% solution freezes at 2℉ (-17℃). When salt is added to ice (or snow), some of the ice melts because the freezing point is lowered. Keep in mind, however, that heat must come from somewhere to melt the ice. The heat that causes melting comes from the surroundings and, in this case, it’s from the warmer cream mixture. By lowering the temperature at which ice freezes, you were able to create an environment in which the cream mixture could freeze at a temperature below 32℉ (0℃) and become ice cream. The shaking (or stirring in an ice cream maker) moves the warmer cream mixture from the inside to the outside of the bag so it can freeze evenly. That way you make a smoother product. It also adds air to the final product so it’s fluffed up a little bit. Yum!

Tags

• camp cooking
• cook
• food
• food fun
• food preparation
• ice cream
• science

Badge Links

• Cook - Cook
• Experiment - Experiment
• Scientist - Experiment
• Skills - Cake