How big is a water droplet?
Description
We have used this very simple activity to develop student�s problem solving and experi-mental design skills. Students are simply asked to answer the single question �How big is a water droplet?� They have 30 minutes to try to find an answer.
Materials
� Pipettes
� Beakers of water
� Rulers
� Scientific scales
Procedure
There is no procedure! We simply tell the students what the question is and leave them to it! Sometimes students are hesitant about doing anything, but if one or two students get started with ideas and trying things out then most of the rest normally follow.
We normally simply provide the students with pipettes and beakers of water. But usually students ask themselves for rulers, or scientific measuring scales. Students have different ways of tackling this problem. Some simply drip some drops on the worktable and then try to measure how wide they are. Some others decide to find out if pipettes of different sizes produce droplets of a different size and start comparing droplets. Others start studying the difference in droplet size that land on different surfaces. It is surprising but students just seem to start making their own hypothesis and start proper experiments without being prompted!
Often students trying to be exact ask for scales and try weighing drops of water. A more advanced technique is to drip say 20 drops onto the scales and then divide the final weight by 20 to show how much one drop weighs. Often students ask, �what do you mean by how big? Do you want the weight, the width, or the height?� There is no answer to this, so we give none. It is up to the students themselves to decide. In one sense this is a meaningless activity, because it is impossible to tell how big a drop of water is, there are simply too many variables, but it is an excellent way of explaining science to students. Sometimes in science there is no �correct� answer either.
Taken from Teaching inquiry-based Science' by Mark Walker.