Back to the list of Innovative Learning Objects
TITLE
Mobile Phone Colorimetry: Color Meter Free
LEARNING OBJECT
Using colours to estimate concentration of solutions
WEBSITE OF THE PRODUCT
NAME OF PRODUCER
vistech
TYPE OF PRODUCT
Mobile Apps
SUBJECT TAUGHT
Chemistry
LEVEL OF KNOWLEDGE
Medium
TARGET GROUP AGE
14 – 16 years old
TUTORIAL SUPPORT
No
DESCRIPTION
This tool is for selecting colours and tones. It can pick and analyse live colours using the camera on an android phone or tablet. The basic version is free and there is a paid version with more features. There are similar apps available for iOS.
The selection of colours is useful for photography and artistic work but it can also be used for basic chemistry as described below.
The colour is measured as ‘Hue-value’ (H-value) and the values recorded for different colours can be used to construct graphs.
The selection of colours is useful for photography and artistic work but it can also be used for basic chemistry as described below.
The colour is measured as ‘Hue-value’ (H-value) and the values recorded for different colours can be used to construct graphs.
INNOVATIVE LEARNING OBJECT
These colour measuring tools can be used to introduce students to colorimetry and spectrophotometry.
Most schools will not have access to spectrophotometers but the principles of the Beer-Lambert Law can be demonstrated using simple coloured solutions, dilutions and the colour-detecting apps.
A standard coloured solution (e.g. copper (II) sulphate solution) can be prepared and then dilutions made. If the solutions are put in volumetric flasks, the phone camera and the app can be lined up to focus on the centre of the bulb of the flask. The distance from camera to flask and background should be the same for each Hue-value (H-value) recorded.
Students can record the values and use them to plot a standard curve.
The teacher can then provide solutions of concentrations known to them but not the students and ask them to find the 'unknown' concentration by recording the H-value and comparing with the standard curve.
We have trialled this simple protocol and found it engaging and informative for the students. A more detailed version can be found in the iStage documents archived from Science on Stage and reported in Science in School:
https://www.scienceinschool.org/content/smartphones-lab-how-deep-your-blue (accessed November 2020).
We do not recommend carrying out the reaction between copper metal and nitric acid to generate the blue solution unless you have access to a working fume hood as the nitrogen dioxide gas produced is toxic by inhalation.
Most schools will not have access to spectrophotometers but the principles of the Beer-Lambert Law can be demonstrated using simple coloured solutions, dilutions and the colour-detecting apps.
A standard coloured solution (e.g. copper (II) sulphate solution) can be prepared and then dilutions made. If the solutions are put in volumetric flasks, the phone camera and the app can be lined up to focus on the centre of the bulb of the flask. The distance from camera to flask and background should be the same for each Hue-value (H-value) recorded.
Students can record the values and use them to plot a standard curve.
The teacher can then provide solutions of concentrations known to them but not the students and ask them to find the 'unknown' concentration by recording the H-value and comparing with the standard curve.
We have trialled this simple protocol and found it engaging and informative for the students. A more detailed version can be found in the iStage documents archived from Science on Stage and reported in Science in School:
https://www.scienceinschool.org/content/smartphones-lab-how-deep-your-blue (accessed November 2020).
We do not recommend carrying out the reaction between copper metal and nitric acid to generate the blue solution unless you have access to a working fume hood as the nitrogen dioxide gas produced is toxic by inhalation.
EXPERT'S COMMENT
Points of strength: visualisation of chemical concepts, engage students
Points of weakness: takes time for the student to learn the software
Pedagogical value: makes abstract chemical concepts visible
Points of weakness: takes time for the student to learn the software
Pedagogical value: makes abstract chemical concepts visible
TEACHER'S COMMENT
While colorimetry is not covered in the 7–9th grade chemistry and physics courses, learning how mobile phones work and how to use their features is part of the technology course, so the app could be used do demonstrate how to use the mobile camera.