Number of potato discs Mean volume of oxygen collected in 60 s / cm3 1 6.1 2 12.0 3 18.2 4 23.8 5 24.1 A science club investigated catalase in potato cells....
Question 1 Report
| Number of potato discs | Mean volume of oxygen collected in 60 s / cm3 |
|---|---|
| 1 | 6.1 |
| 2 | 12.0 |
| 3 | 18.2 |
| 4 | 23.8 |
| 5 | 24.1 |
A science club investigated catalase in potato cells. Catalase breaks down hydrogen peroxide into water and oxygen. Potato discs of equal diameter were placed in hydrogen peroxide solution, and oxygen was collected for 60 s. Table 1 shows the mean volume from three trials. The club kept the temperature at 20 degrees C.
(a) Complete the calculation of the mean rate of oxygen production using the result for 4 potato discs. Give your answer in cm3 per minute. [3]
(b) Explain the pattern in the results as the number of potato discs increased. [4]
(c) Describe three steps that would improve the reliability of the mean volumes in Table 1. [3]
(d) State three variables that should be controlled in this investigation. [3]
Answer Details
(a) For four potato discs, 23.8 cm3 of oxygen is collected in 60 s, which is 1 minute.
\[\text{mean rate}=\frac{23.8\text{ cm}^3}{1\text{ min}}=23.8\text{ cm}^3\text{ min}^{-1}\] [3]
(b) More potato discs contain more cells and therefore more catalase molecules and active sites. More hydrogen peroxide molecules can be broken down per second, increasing oxygen production. The rate levels off because hydrogen peroxide becomes limiting or is used up. [4]
(c) Repeat each condition more times, calculate a mean, identify and repeat anomalous results, use a gas syringe with a finer scale, and ensure apparatus is airtight. Any three. [3]
(d) Control hydrogen peroxide concentration or volume, temperature, disc diameter or thickness and hence surface area, collection time, potato source, and pH. Any three. [3]
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