P3 estimate the purity of samples using scientific techniques P4 use instruments/sensors to test substances or materials.
M3 justify the choice of instruments in the practical exercises.
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P4 – Use instruments/sensors to test substances or materials.
M3 - Justif the choice oi instruments in the practcal exercises.
D3 - Evaluate the accuracf oi the measurements taken.
Measuring pH in diferent substances
Aim: to determine the pH using a data logger and compare the results to the pH suggested
by the manufacturer.
Equipment:
1. Data logger
2. Chosen substances to test
3. Pure water
Method:
1. Set up the data logger and get ready to test the substances for their pH.
2. Add distlled water to solid substances such as toothpaste and mix well.
3. Start with any substances really, there doesn’t have to be a specifc sequence, take
out the data logger from its secure holder cap and turn it on.
4. Place the yellow end of the data logger into the soluton you are testng for pH and
press the green button to start the logging of the pH.
5. Wait at least a minute for the data logger to stabilise and determine the results, you
will fnd that the pH would change but then would stop going up or down at some
point – this is the value you will record on your results table.
6. Test all of the substances given and record your results.
7. Compare the results obtained with the ones provided by the manufacturer and
calculate the error – take away the value manufacture gave from your results.
Results:
pH recorded pH suggested by error
manufacturer
Lemon juice 3.0 2.3 -0.7
Baking soda 7.2 8.4 -1.2
Milk 6.6 6.6 0
Black cofee 5.4 5.0 -0.4
Tomato juice 4.4 4.1 -0.3
Distilled water 4.2 7.0 -2.8
toothpaste 7.2 9.9 -2.7
Conclusion and Evaluation:
Only one of the results which I have measured with the data logger has shown an exact
replicate pH as the one provided by the manufacturer. Other results all had some errors
which might have or might have not been due to the accuracy of the data logger. However, I
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