November 2013

# Microscale hints from across the pond

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Bob Worley FRSC, MSc, BSs, CLEAPSS, The Gardiner Building, Brunel Science Park Kingston Lane, Uxbridge UK

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It was a great privilege to meet so many Canadian and American chemistry teachers and lecturers at the superbly run ChemEd 2013 conference at the University of Waterloo. It was very brave of the organizers (and indeed myself for that matter) to organise a workshop over a 3,700 mile distance and a rather large stretch of water. In fact, I often ask myself why I do it. Well there is still a passion for the subject inside me even in my advanced years and when a voice suddenly shouts out in the workshop, “hey, this is cute”, I then have the answer.

I am often asked why any teacher in the UK should try the microscale approach when the traditional methods have served us well for 120 years! I have been heavily involved while working (and still do) for CLEAPSS dealing with safety in the school laboratory in the UK. When carrying out a risk assessment of a procedure, one of the methods we often adopt is to reduce the scale of the procedure. The microscale approach is one such measure and although practiced by many teachers in other countries in the world, it is met with much derision by the traditional school chemistry teacher. So I made a list of points which I have published in the Education in Chemistry journal.1

If a microchemical approach satisfies one or more of the following points it should be seriously considered.

1. It allows a once–dangerous experiment to be carried out more safely.
2. It shortens practical time so that lessons are not so rushed.
3. It reduces the cost of equipment and consumable materials.
4. Users report a higher level of concentration amongst pupils and mistakes are quickly rectified. Bob Worley at ChemEd 2013
5. It enables some stunning visible
   effects when filmed or projected onto a whiteboard.
6. It reduces teacher/technician time in disposing and cleaning up.
7. It reduces waste, a factor that is becoming more important in the UK. (We would, in fact, consider many other countries to be draconian in their constraints on waste from a school laboratory).
8. It shows equivalent or better quantitative results (although comparison of techniques is a useful exercise in error analysis). However, by coming to Canada, I can now add another point.
9. It enables the teacher to help the students develop a deeper understanding of the chemical processes that are taking place; how we interpret the visible with the invisible. To illustrate the point, why not carry out the following little experiment.

## Diffusing ions!

Print out a drawing as shown right and insert it between the leaves of a plastic office folder.

Now place a few crystals of copper(II) sulfate pentahydrate in one little circle on the right and a few specks of anhydrous sodium carbonate on the other little circle. The reaction will take place on the plastic sheet.

Now drop distilled or deionised water between the two little circles so it just incorporates the two solids. Wait for a few seconds and see the effects.

How can you explain the formation of the band of copper carbonate forming in the hemispherical droplet without recourse to the crystals breaking up (you can actually see the dissolution as the changing density of water in the droplet alters the refraction angle of light). This culminates in the particles coming together to form a precipitate as a band across the droplet. So all we have to do now is to convince the students that the particles are ions!2

Why not try some other combinations? The potassium iodide and lead nitrate system is particularly beautiful. Why not project this onto a screen using a good webcam or a video microscope? Or students could take their own pictures with their cameras.

## A series of articles?

Could the microscale approach become a (semi-) regular series in Chem 13 News? Why not send in your ideas, hints and photographs of your inventions and the students doing them. We can check their work and publish them in the magazine. If teachers see other teachers using these techniques, they are more likely to have a go themselves.

## Disposal

You just wipe over the sheet. You will need to follow local disposal rules if you do the lead iodide demo.

## Reference

1. Microscale Chemistry Revisited, Education in Chemistry, May 2012. (If you would like a copy of this, please contact the author.)
2. Demonstration photos on back cover.

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