As described in our blog on ‘Copper Ore’, colorimetry is a simple technique that can be used to develop measurement skills in pupils. Recently we have been experimenting with using smart phone apps to enhance the experience and bring technology into our work.
Initially we used a single Android phone and an app from the play store (Color Grab by Loomatix). The pupils carried out the activity as described in the ‘Copper Ore’ post and then one of the outreach team made the measurements.
The whole exercise turned out to be very engaging and rather than focusing on the copper ore aspect of the exercise we ran it as an informal practical test with a mixed Year 5 and 6 group to see how well they had learnt basic measuring skills. It proved to be very popular and class achieved some excellent results.
It turns out that a white background behind the coloured solutions is essential, as is a consistent lighting and distance from the sample for each groups results.
The app measures the colours and provides HSV values (Hue, Saturation, Value). The hue corresponds to the shade of the colour you are measuring so as long as you measure solutions of the same chemical (or dye) then H corresponds to the intensity of the colour and is directly related to the amount of compound or dye in the solution.
Using this idea, the colour scale produced for example by a series of solutions of
copper sulfate can be measured and used to find the amount of copper in an unknown sample.
We then extended the use of technology further when working with Year 8 students by showing them how to create a chart of ‘amount of copper sulfate vs H value’ using google docs on their class Chromebooks.
This allowed them to ‘see’ how well they had carried out the dilutions and measurements in their experiment. For our own information we added a linear regression fit to measure ‘R-values’ and were pleasantly surprised to see how linear the data was for an initial trial.
We have now bought some low cost phones and have removed most of the extraneous apps and intend to use them as a class set of colorimeters. The only difference will be the choice of app, ColorGrab won’t run on the older Android operating system (Gingerbread) so we have gone for a similar app called Color Picker that allows HSV to obtained from a photo taken of the sample.
Next step is to use them with a class.
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