Can you think of a more delicious way to demonstrate the properties of matter than by making ice cream? You don't need any fancy equipment to make this treat, just a few items you probably already have and some kid power.

You need:
Gallon size zipper bag
Pint size zipper bag
2 C whole milk or cream
pinch of salt
ice cubes
a kid or two

-Pour the milk/cream into the smaller of the zipper bags. Add a pinch of salt.
For extra credit you can add a small amount of chocolate syrup, vanilla, or pureed fruit.

-Place the smaller bag inside of the large zipper bag. Fill the large bag with ice and close.

-Shake! Shake! Shake! It will take about 10 minutes of constant shaking, but you will see the milk transform into ice cream before your eyes!