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The heat's on when revisiting topics

It's always a challenge to follow secondary science topics taught at KS3 with a fresh approach at KS4. There is so much overlap and although KS4 requires greater depth it is difficult to avoid repeating yourself. I find alternative approaches to practical work help, as with one such topic, conduction.

At KS3 I use the classic conduction experiment of heating rods of different materials from one end, each having equal amounts of petroleum jelly holding a paper clip placed at the same evenly spaced intervals along the rod. As materials conduct, pupils observe the Vaseline melting and the paper clips falling at different times. They can measure these to identify a rate of conduction.

At KS4, I use the same rods, each loosely held vertically by a clamp. The bottom of the rod being tested rests on some cling film stretched across a plastic beaker with some ceramic paper in the bottom. The top of the rod is heated using a Bunsen burner clamped sideways. The time taken to melt the cling film so that the rod drops is recorded and can be used to identify how quickly a material conducts.

This immediately opens up opportunities for SC1 activities. For example, if you have material rods of different thicknesses how does this affect the time taken to conduct? Thought is required in the planning and analysing of an investigation asking the question, "How does the length of a material affect its rate of conduction?" All the practical work has opportunities for in-depth evaluations, with many variables to consider (heat loss and tension on the cling film, for example). An interesting aside can be to use the dropping of a rod to trigger a switch for a heat alarm or for students to design and arrange their apparatus to measure one minute. As with all practical work you need to be sure of your class and carry out a thorough risk assessment.

Stuart Bennett

Head of science, The Aveland High School, Lincolnshire

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