Justin Coope, a fudge and toffee maker, explains how important it is to measure the temperatures of fudge or toffee mixture carefully to ensure it doesn't become too soft or too hard when it cools. He explains he needs to heat fudge to 118 degrees Celsius while toffee needs to be heated to 140 degrees Celsius. He uses a digital thermometer to measure the temperature. Chocolate burns more easily and can only be heated to about 30 degrees Celsius.

This clip is from:
Science Clips, Keeping Warm
First broadcast:
9 October 2007

This clip can be used to extend knowledge about the differing melting points of solids, as well as introducing children to the concept of chemical and physical changes. Pupils can safely investigate the different melting points of materials such as chocolate, wax, ice and butter in class, observing the changes that occur once the substances are cooled, as well as noting that the processes are reversible and therefore physical changes.
The clip explores the practical application of such processes, showing how careful scientific measuring (of temperature) occurs in confectionery production. Pupils could be asked to suggest whether they think the process of making fudge and toffee is a physical or chemical change. Is a whole new product formed? Equally, discussion about the optimum storage conditions for the confectionary is a good opportunity to assess their understanding of the differing melting points of chocolate and toffee. If the chocolates were left in a sunlit window, what changes would occur? What about the fridge?