The table below shows the results of a food-science investigation using catalase from potato. Catalase speeds up the reaction in which hydrogen peroxide sol...
Question 1 Report
The table below shows the results of a food-science investigation using catalase from potato. Catalase speeds up the reaction in which hydrogen peroxide solution forms water and oxygen. A student placed equal-sized potato cylinders into 20 cm3 of hydrogen peroxide at different temperatures. The maximum volume of oxygen was measured after the reaction stopped. Fig. 1 shows the gas collection set-up used for one temperature.
| temperature / degrees C | maximum volume of oxygen / cm3 | time to collect 20 cm3 oxygen / s |
|---|---|---|
| 10 | 36 | 180 |
| 25 | 36 | 82 |
| 40 | 36 | 39 |
| 65 | 8 | not reached |
Table 1
Answer Details
Note: The supplied stem provides Table 1 but does not show the lettered questions. The answers below are organised according to the supplied mark scheme.
(a) The maximum volume of oxygen at \(40\ ^\circ\mathrm{C}\) is \(36\text{ cm}^3\). [1]
(b) At \(40\ ^\circ\mathrm{C}\), the rate for collecting \(20\text{ cm}^3\) is:
\[\frac{20\text{ cm}^3}{39\text{ s}}=0.5128\ldots\text{ cm}^3\text{ s}^{-1}\]
This is \(0.51\text{ cm}^3\text{ s}^{-1}\), accepted as \(0.5\text{ cm}^3\text{ s}^{-1}\). [2]
(c) \(40\ ^\circ\mathrm{C}\) gives the fastest rate in the table because it reaches \(20\text{ cm}^3\) in the shortest time, \(39\text{ s}\). [1]
(d) Catalase is a protein enzyme. At \(65\ ^\circ\mathrm{C}\), high temperature changes its shape, or denatures it. Fewer active sites are available, so there are fewer successful reactions and far less oxygen is made. [3]
(e) Two suitable control variables are the volume and concentration of hydrogen peroxide solution. The mass, size or surface area of the potato cylinders, measurement time, and apparatus should also be kept the same. [2]
(f) The biological catalyst is catalase. [1]
(g) A gas syringe is better than judging bubbles because it measures gas volume quantitatively and gives a more precise result. [1]
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