Three objects are made from different pure metals. It is possible to determine the type of metal from the temperature at which the it starts to melt. A pyrometer measures very high temperatures. The lead melts first, followed by the aluminium and finally the copper. At the foundry, metals are melted and poured into casts. When the liquid metal cools it solidifies again into the shape of the cast.

First broadcast:
9 October 2007

Students could be asked to recap how the presenter in this clip was able to identify the three different types of metal – by their melting points. They could then discuss other possible criteria for identifying lead, aluminium and copper. Students could also research the melting point of other metals and make their own labelled thermometer like that in the clip.

Challenge students to find the melting points of different types of chocolate. They could first predict which they believe will melt faster – milk, dark or white chocolate. They could also consider how they can ensure it will be a fair test, for example using the same size of pieces and the same weight of chocolate. Students could then heat the chocolate very slowly, either with a heat lamp or over hot water, and record the temperature at which it starts to melt. They could record results and assess whether their predictions were correct.