Ice Cream in a Bag

What you need:

• 1 quart-sized Ziplock bag

• 1 gallon sized Ziplock bag

• Ice

• Salt—rock salt or ice cream salt works best

• Half & Half

• Sugar

• Vanilla

• Measuring cups

What you do:

1. Combine 1/2 cup of half-and-half, 1 tablespoon of sugar and 1/4 teaspoon of vanilla in the quart-sized Ziplock bag and seal tightly.

2. Fill the gallon sized bag halfway with ice.

3. Add six tablespoons of salt to the ice.

4. Place the quart-sized bag into the gallon-sized bag. Seal the gallon bag tightly.

5. Now, start to shake and knead the bag. It will get very cold!

6. Once your ice cream mixture seems fairly solid—the texture of soft serve—take the quart-sized bag out and enjoy!

Questions to ask:

1. What do you see, smell, hear, feel or taste at different stages of the experiment?

2. How did the ice cream mixture change from the beginning of the experiment to the end?

What's the science:

This activity shows a change in the states of matter. The half and half and vanilla begin as liquids, meaning that they take the shape of their container, have a defined volume (amount of space they take up) and are easily poured. The molecules inside liquids move quickly and easily slide past each other. As the mixture starts to cool, the molecules in the ingredients begin to slow down and turn into a more solid state.

Solids have defined volumes, but do not take the shape of their container. One of the reasons this change of state happens so quickly is because of the salt added to the ice. That's because salt lowers the melting point of ice.

This activity also shows an example of a chemical change. Once the ingredients are combined, you can no longer separate them, like you could if you pulled out the carrots of a salad. Chemistry plays a huge part in making foods like this ice cream, cake, bread and cookies. Now you see that chemistry can be delicious!