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Grant Stott takes a look at the invention of tarmac. Roads used to be made from clay, earth or chalk, but these materials were very messy. John McAdam thought it would be easier if the roads were covered in small stones and invented tarmac. It took his company 30 years to cover all roads across the UK. The process involved spreading hot tarmac onto a road, adding lime chippings, and finally flattening the surface with a steam roller.

Please note this clip ends a little abruptly.

Students could be given various substances to examine such as clay, mud, soil, tarmac, rubber, pebbles and so on. Challenge students to list the properties of these materials - hard, soft, crumbles easily, wet, dry - and then carry out an investigation to discover which material would make the best road surface.

By recreating some of the conditions a road might be subjected to, such as rain and vehicle usage, students should be able to list the advantages and disadvantages of each material. By watching the clip as a plenary, the suitability of the harder materials, such as tarmac, will be emphasised.