'Cracking apart'. Ask pupils to discuss situations where materials expand in the heat and contract in the cold out of doors. Examples might include steel bridges, or concrete roads; in both cases, expansion joints have to be included to allow for the movement. Explain that rocks also expand and contract and that this can lead to their break up. This is a form of physical weathering. Small chips of granite and other rocks are heated in a Bunsen flame and then rapidly cooled in water. This is repeated to investigate the rate at which they ‘weather’ by breaking apart.
This is one of many Earthlearningideas which encourage pupils to take part in an activity and then relate their findings to the world around them.