Biology 5090/32 — October/November 2017
Cambridge O-Level · Practical Test · worked solutions for every part, with the mark scheme
Topics Observations and Measurements · Analysis, Conclusions and Evaluation · Experimental Contexts · Planning Experiments and Investigations · Microscopy and Biological Drawing · Use of Techniques, Apparatus and Materials
You are going to carry out an investigation to determine the concentration of glucose solution X.
Benedict’s solution is used to test for reducing sugars, such as glucose.
You are provided with Benedict’s solution and 5 test-tubes containing of:
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distilled water labelled W
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0.2% glucose solution labelled A
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0.4% glucose solution labelled B
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0.6% glucose solution labelled C
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unknown glucose solution labelled X.
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Using the measuring cylinder or syringe provided, add of Benedict’s solution to each of these 5 test-tubes.
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Put the test-tubes in a beaker to act as a water bath.
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When ready, raise your hand to request hot water which the Supervisor will pour into your water bath. Caution: the water will be hot.
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Note the time when the hot water was added to the water bath ______
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Leave the test-tubes for 10 minutes. While you are waiting, answer question 1(c).
After 10 minutes remove the test-tubes from the water bath and place them in the test-tube rack.
Record the time ______
Observe the appearance of the contents of each test-tube and record your observations in Table 1.1.
Table 1.1
| test-tube | glucose solution concentration (%) | observations |
|---|---|---|
| W | 0.0 (distilled water) | |
| A | 0.2 | |
| B | 0.4 | |
| C | 0.6 | |
| X | unknown |
Leave the test-tubes in the rack for a further twenty minutes.
While you are waiting continue with the other questions.
Using your observations in Table 1.1, estimate the % concentration of glucose solution X.
concentration of glucose solution X = ______
Explain how you reached this estimate.
______
Suggest how you could determine a more accurate % concentration for glucose solution X.
______
You are given a 1.0% glucose solution. Describe in detail how you would use it to produce of a 0.5% glucose solution.
______
Explain why you were asked to test the distilled water with Benedict’s solution.
______
After the test-tubes have been left for twenty minutes, observe them and answer questions 1 (e)(i) and (ii).
Describe any differences in appearance of the contents of the test-tubes containing glucose solution, after they have been left in the rack for twenty minutes.
______
Solids are often formed after the Benedict’s test. Suggest how you could separate any solid produced after the test and obtain its mass.
______
The rest of this paper
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