practical report
A group who had been assigned a time of 70 seconds in the practical went about their experiments as follows. The made up a number of test tubes each containing 150 µL of 1% potassium iodide, 150 µL of 3% hydrogen peroxide and 100 µL of starch water. This caused development of the blue-black colour characteristic of the starch-iodine test. They then added a range of volumes of 50 mM ascorbic acid and recorded the time for which the colour disappeared. These are the data that they obtained:
Volume of Ascorbic Acid (µL) Time (s)
22 15.37
39 36.25
88 59.56
99 58.71
111 84.90
123 66.94
136 106.06
150 108.57
350 151.94
The group used a volume of 123 µL of ascorbic acid in their time trial.
For your assessment:
1) Comment on the group’s choice of volume and say what conditions you would have used for the time that your group was given*. Explain clearly how you arrived at your answer.
2) Say how you would have improved upon this group’s design referring to experimental principles: hypothesis, treatment, control, observation, interpretation. Consider the target time assigned to your group* for the practical lab in planning your answer.
3) Write a methods section for the procedure you propose in correct scientific English and style as if it were being reported in a scientific paper after the conclusion of the experiments.
Also, include the table above and its graph in the appendix section.
