Review

UniServe Science News Volume 10 July 1998

Chemistry Prelabs II

Chemistry Prelabs II is a simulation package for chemistry experiments. It allows the user to practise experimental techniques in safety, before entering the real laboratory. There are 12 pre-labs on the CD, which covers basic experiments such as chromatography, corrosion of metals and acid-base titrations.

This program invited me (with an uncontrollably loud voice) to put on the required safety lab coat and glasses, pick one of the 12 first year level experiments on offer, and enter the virtual lab wearing my gum boots (well that's what it sounded like!) through a squeaky door. The virtual scene was graphical rather than a photographic image of a real lab.

I like baths so I chose to analyse Radox Bath Salts. A lab notebook gave me instructions on what to do next, and I had access to:

• a calculations book with spaces for me to insert calculations, with a calculator to help me;
• a techniques book with text and QuickTime movies describing a range of experimental procedures;
• an equipment book to describe the glassware I would be using;
• a chemicals book with brief safety information on each chemical I would use; and
• a glossary book with brief meanings for important terms.

This titration experiment required me to use a pipette to transfer 25.00mL of Radox solution. The only way I could do this was to click and drag the pipette to the volumetric flask and remove the solution directly from the flask. I didn't think this was good technique so I checked with the demonstration movie in the techniques book and was shown, more correctly, solution removed from a beaker using a pipette. One of the problems with using graphical simulation in a virtual lab is that there are inevitable simplifications. Whether they can reinforce or lead to poor technique is debatable.

I was able to click and drag my way through three titrations using a clever simulation of using a burette. However, in each case I was not encouraged, or able to:

• do a rough titration to find the approximate end points, without having to count it in my titre averaging;
• add solution with split drops; or
• read the burette clearly to two decimal places.

However, perhaps this fine tuning is best taught in the real wet lab, and the function of the simulation is to give a simplified overview. The videos on this and other techniques could be criticised by an analytical chemist for small omissions, and by a video producer for not showing sufficient close-up views, but once again, the fine technique details should come later in real time, with directions from a real demonstrator.

The calculation protocol requires a stepwise progression of mini-calculations set out for the student, without any need for thinking. Not all chemists work this way - many accumulate the steps into one long calculation at a suitable point. This habit is recommended to avoid compounding rounding-off errors. I would also have preferred to see units associated with every quantity, and cancelled out, to encourage students to think about any unit conversions required, and as an internal audit of correct formula rearrangements. However, perhaps these calculations are also designed as an overview before students have to do the real thing in the lab on their own.

Despite some strange sound effects, a calculator that must be turned off before you can type in a result, and some pedantic criticisms of technique, this program provides a useful 'dry run' to a variety of common experiments. As such it is a good solution to the problem of encouraging students to preview an experiment without stress, before they enter the lab with an over-zealous demonstrator looking over their shoulders.

[Author's response:

• Students are not expected to include titration results if they are not within the range required. Indeed the results will not be accepted if they use all values in such an instance.
• Burette readings are required to 2 decimal places - the last figure is always estimated even in the wet lab.
• Stepwise calculations are provided to assist those with low short term memory capacity in these early stages of tertiary chemistry.
• An important feature is that students may access the material at their own pace and when and as often as they wish in their preparation on either a PC or a MAC.]

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