Do you want to introduce young children to the science of magnets?
Magnets (we used delightful magnetic car sets from http://www.windmill.net.au )
Paint in squeeze bottles or tubes
Paper plates or thick card
The children blob small amounts of paint onto the card or plate and drive the magnetic car though it creating tyre marks all over their plate. The magnet goes under the plate while the car, or other metal object, is above. If you choose to use primary colour paints this activity will also highlight the properties of colour mixing.