Scrumptious Science: Making Ice Cream in a Bag

A chilly, edible chemistry challenge from Science Buddies

Apr 25, 2014

George Retseck

Key concepts Food science Chemistry Freezing Phases of matter Solutions Introduction Have you ever made homemade ice cream? It can be a lot of fun, and you end up with a tasty frozen treat! A lot of interesting chemistry is actually needed to make ice cream. For example, think about how you start out with refrigerated (or even room-temperature) ingredients and then need to cool them down to turn them turn into ice cream. How do the ingredients change during this process? How important do you think they get cooled to a certain temperature? In this science activity you'll make your own ice cream (in a bag!) and explore the best way to chill the ingredients to make them become a delicious reward! Background To make ice cream, the ingredientstypically milk (or half and half), sugar and vanilla extractneed to be cooled down. One way to do this is by using salt. If you live in a cold climate, you may have seen trucks spreading salt and sand on the streets in the wintertime to prevent roads from getting slick after snow or ice. Why is this? The salt lowers the temperature at which water freezes, so with salt ice will melt even when the temperature is below the normal freezing point of water. Technically, the temperature that the salt lowers is called the freezing point. When a freezing point is lowered, such as by adding salt to water, the process is called freezing-point depression. As we'll see in this activity, freezing-point depression is not unique to solutions made of water and salt; it also happens with other solutions. (A solution is made when a substance, such as salt, is dissolved and becomes a solute. The medium into which it is dissolved is a solventtypically a liquid, like water.) Materials

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Scrumptious Science: Making Ice Cream in a Bag