day 5
materials
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Whole milk
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Vanilla extract
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Sugar
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Salt (both table and rock work, but may give different results, rock salt is recommended)
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Ice
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Large (gallon-size) and small (sandwich or quart-size) Ziploc bags
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Measuring spoons
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A large tray or plate (to contain the mess)
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Optional: soda for soda floats
steps
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In the small ziploc bag, add 1 cup of milk, 2 tbsp of sugar, and ½ teaspoon of vanilla extract, and seal.
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Add 4 cups of ice to a large, gallon-size bag (no salt yet!) and then put in the prepared small bag, making sure both are sealed shut.
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Shake the bag for a couple minutes and observe. Do you see any changes yet?
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Then, add ½ cup of salt to the large bag (not the small one!),and shake the bags for another 5 minutes.
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Once the milk has solidified, it’s ready to eat! Serve as is or turn it into a tasty ice cream float.
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Enjoy your tasty treat!
the science
The freezing point of a substance is the temperature at which a substance changes from a liquid to a solid. For water, this temperature is 0 ̊ C. Adding salt lowers the temperature of the ice to below 0 ̊ C, by lowering the freezing point. This allows the temperature of the ice to freeze the milk.
Taking it further
Try making your ice cream with alternative milks like almond or oat. Did you have to shake the bag for a longer period of time? This is why we add salt to icy roads! It lowers the freezing temperature and keeps ice from forming on the roads.
Interactive simulation of the states of matter
Inspired by ScientificAmerican
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