Why can't you make a bicycle completely out of rubber? A manufacturer describes the different materials needed to make the different parts of a bike. He discusses the importance of a rigid steel frame which is strong but light and the rubber tyres which are important for comfort and grip while still being tough. Plastic is then discussed as a lightweight material useful for any 'extras' found on the bike, as it can be moulded to any shape.
Children could design their own bike and label the parts with the materials and their properties, explaining why each material would work well on that part of the bike. The children could then watch the clip and compare the ideas of the manufacturer to their partner's ideas. They could then discuss their work and attempt to improve it based on suggestions from the clip and their partner.