Ice Cream Machine

This edible science experiment explores temperature and teaches how materials are affected by heating and cooling.  

Supplies

• 4 oz (½ cup) of milk
• 4 oz (½ cup) of cream
• 1/4 tsp of vanilla (or use other flavors usually found near the vanilla in a grocery store — you can use chocolate syrup for chocolate ice cream)
• 4 tsp of sugar
• A few drops of food coloring (optional if you want colorful ice cream)
• Lots of ice
• ½ cup of salt. Rock salt (sold at hardware stores) works best.
• Small (quart size) zip-lock freezer bag
• Extra large (gallon size) zip-lock freezer bag
• Thermometer (optional)

What science concept is this activity teaching?

This experiment teaches that materials are sometimes changed by heating or cooling and that by observing such changes, we can infer how hot or cold an object is. Kids will learn that thermometers provide a helpful way to measure and describe the hotness or coldness of things— a more accurate measure than relying on our own senses.

Why do you need salt to make ice cream? Why didn’t we need a freezer?

When salt is added to ice, the chemical reaction between the two, forces the ice to melt. Before the ice can melt, though, it needs to borrow heat from objects that surround it. This is called an endothermic process. Since your dairy ingredients are not as cold as the ice, it borrowed heat from your cream and milk, making them colder. When they get colder, the water molecules freeze turning milk and cream into edible ice cream. Yum!