How does heat change materials? Includes footage of a glass blower working with glass. Glass starts as sand, and when it is heated to a high temperature it melts to form liquid glass. When it is hot it can be formed into different shapes then cooled to become solid again.

First broadcast:
1 October 2007

This clip could be used to remind pupils about the different states of materials and how some can change due to heat. It could help illustrate the idea of reversible and irreversible changes of materials that could then lead to a series of hypotheses and investigations into other common materials. The pupils could be encouraged to explore dissolving and recovering materials such as salt and sugar, plus changes to margarine, cheese, chocolate, bread and wax following heating and cooling. The formation of glass in the clip demonstrates how some changes form new materials. The clip could be used to initiate discussion about the suitability of materials for their purpose and of the principle of functionality over form.