Eleven thousand years ago Siberia was an even colder place than it is today. Stone Age man made a discovery and invented pottery. It was noticed that clay left out in the sun dried and became hard but was brittle and broke easily. Dried clay would become soggy again if left out in the rain. Fires were used to keep people warm and to cook food. When these fires were made on top of ground which contained clay, the ground around the fire changed and became stronger. Clay vessels baked in fire became pottery. It is believed the origins of pottery date back to the Ice Age. The process is still very common and used today.

First broadcast:
4 March 2008

Students could explore the different properties of clay, and how these change through drying and firing. Working in groups, students could be given three vessels made of wet clay, dried clay and fired clay and asked to describe the properties of each. Students could then predict which would make the best drinking vessel. They could design and carry out an experiment to test their prediction, recording the changes to the clay when liquid is added.

Ask students to discuss the irreversible change that occurs when clay is heated at high temperatures. Challenge students to explore other reversible and irreversible reactions by heating a number of substances and recording the changes. Examples could include ice or raw egg. They could then cool these and note if it returns to its original state. Students could then organise these into reversible and irreversible reactions.