Demo chains

25 04 2012

ImageA science teacher gets two years to teach a group of children. A science presenter typically gets between 20 mins and one hour. Can science presenters teach anything in such a short space of time? How can science presenters make the most of the short time they have with their audiences? One answer is demo chains.

Before you can effectively teach anyone anything you first need to find out what that person knows about the subject- there is no point trying to show someone the effects of increased air pressure if they don’t know that air weighs anything.

You also need to find out what they think they know but actually don’t know or only understand partially- it is no good trying to teach someone about generating electricity by moving magnets in copper coils if they believe all metals, including copper, are magnetic.

Only once you have filled in the educational blanks and repaired those damaged bits of knowledge you can begin to build further understanding. This is why formal teaching takes so much time.

In science presentations before we perform demos or introduce concepts we should also check for gaps in knowledge and address misconceptions but how can we do this in the short time we have? The best way to do this is with demo chains.

Let’s imagine we are trying to demonstrate that ‘air pressure is exerted in all directions’. Instead of showing a single air pressure demo, let’s say the upturned cup and card trick, and hoping they understand what is going on you should craft a series of demos that will help your audience understand.

Before we start we might get our audience to waft air with their hands against their faces so they are reminded they are surrounded by air. Then we could do one demo to show air is pushing down, a second to show that air pushes sideways as well as down, before finally showing the third demo in the chain which is the upturned cup.

Hopefully by using a chain of demos we will have brought everyone up to speed before they see the upturned cup. Hopefully the will understand about the pressure pushing in all directions better than if they had just seen that demo by itself.

A nice way to think of this technique is as a bus journey. Instead of just plonking people at their final destination different people are picked up at different stops on the route. Everyone is taken on the same route, which might be totally familiar to some, partially familiar to others and totally new to a few, but they all get to see the same route before finally being dropped off at the end of the line.

When we perform demos singly we are assuming too much of the audience. Why take the risk that there might be missing or damaged pieces of understanding that will render your demo meaningless? A much better strategy is to design a demo chain to bring everyone up to speed before you then take them further.

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