Demo vs Experiment

Science fair gone wrong

In #articles

I was a judge for a local science fair this past week, and found a number of projects lacking. After thinking about it for a while, I realized that one of the problems seems to be the distinction (or, rather, lack of distinction) made between demos and experiments. In teaching science, especially in the younger grades, it seems common to say something like "today we are going to do an experiment, mixing baking soda and vinegar". This, to me, is not an experiment. So, what do I think is the difference? Here are a few thoughts. Are there any more?

  1. The outcome of an experiment is unknown, whereas the outcome of a demo is known - deliberately.
  2. In an experiments, the variables are quantifiable, whereas the variables of a demo are typically discrete and not quantitfiable.
  3. In an experiment, the outcomes are also quantifiable.

To continue with the example, the following demos would be bad science fair topics:

  • what happens when we mix baking soda and vinegar?
  • which produces more gas, baking soda and vinegar or baking power and vinegar?

To make them true experiments, we could ask

  • how does the amount of gas produced with baking soda and vinegar depend on the quantity of baking soda? (both the amount of baking soda and the amount of gas are quantifiable)
  • to follow up, how does the amount of gas produced with baking powder and vinegar depend on the quantity of baking powder? Is this the same as the dependence on baking soda?

So how many of the "experiments" shown in, for example, this science fair site are actual experiments? The first few I checked did not meet the criteria above for experiment, but one could possibly modify them to do so. However, without this guidance, the students are left with a sterile view of science.