1. Fill the plastic container up with water.
2. Place
the lid securely on the plastic container.
3. Place the container in the freezer, giving it
plenty of time to freeze (over night would be good).
4. Take the container from the freezer.
What has happened to the water? When water gets extremely
cold it changes its form and turns from a liquid (water) to a solid
(ice). Water takes up more space when it freezes. As the water changes
to ice it expands and pushes the lid off the container (as the
ice needs more space).