1. Stick the rim of the bottle lid around the centre of the printed side of the CD using strong glue. Take care to ensure the seal is complete.
2. Decorate the CD with permanent marker pens.
3. Inflate the balloon, using a balloon pump if necessary, and twist its neck to ensure the air doesn’t escape.
4. Make sure the bottle lid is pushed shut, then stretch the neck of the balloon over the bottle lid. Note: Generally this is easier to achieve with two pairs of hands!
5. Place the hovercraft on a flat surface, such as a table or the floor.
6. Ask the children to try pushing the CD hovercraft when the balloon is inflated but the air is not free to escape, and take a measurement of how far it travels.
7. Ask the children to open the lid and give the same push to the hovercraft, and take a measurement of how far it travels. How does this motion compare?

We had great fun making and decorating our hovercrafts and they definitely went further when they had the cushion of air to help lower the amount of friction.