Mean beans

8th February 2008 at 00:00

Edible models are a tasty way to illustrate concepts. A Scotch egg earth and jelly bean chromosomes helped Sarah Longshaw.

Models can be very useful when teaching science. They help kinaesthetic learning and aid visualisation (often of very small things). They let teachers assess pupil knowledge and understanding, and help to develop pupils' skills in evaluation. They can help lessons be memorable and fun.

Recently, I have concentrated on the use of food. It is always popular if pupils can eat the results at the end. Year 10 has made hydrocarbon molecules from jelly beans, using different colours for the different atoms (red for carbon, yellow for hydrogen) joined by cocktail stick bonds.

Jelly beans also make good chromosomes - they can be used to show the processes of cell division, particularly if you use different colours for the maternal and paternal chromosomes.

Smarties now contain only natural colours, so can't be used for chromatography. But they can be used as electrons to help A-level students visualise mechanisms in organic chemistry. Other craft materials can be useful too. Coloured beads, pipe-cleaners and bobbles can be transformed by A-level biologists to show the 3-D structure of protein.

Getting students involved helps them understand (or at least remember) a concept. One of my more memorable Year 13 biology lessons involved acting out "the sodiumpotassium" pump (involved in transmitting nerve impulses). Students acted as membrane proteins, while balls labelled to represent the ions involved were transported (hurled) from one side of the membrane to the other.

Other topics lend themselves to modelling. In Earth science we show tectonic plate movement with broken cream crackers "floating" on tomato soup, heated in a large glass beaker or pyrex bowl, as we ask the students what each represents and describe the convection currents in the mantle (soup).

Discussing the limitations of a model enables pupils to demonstrate their understanding. Is it a good model, can they suggest something better? Year 10 believed the Scotch egg representing the Earth's structure was, on the whole, a good model. Although the shape was not quite right, and not all the layers should be solid, the fact that they would remember them was more important.

Significantly, they were all interested in the subject - particularly when we discussed whether a Creme Egg could be adapted to make a better model. Or perhaps more when we were trying to decide which model would be worthy of winning the Creme Egg.

Sarah Longshaw teaches at All Hallows Catholic College in Macclesfield, Cheshire.

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