Biology Practical Worksheet Raw Marks: ………….. / 40 = …………………..
Name: ………………………………………………………………………………………………… Submission Date: 06-Nov-2023
(a) A student investigated the effect of different concentrations of sucrose solution on the movement of water
into and out of potato cells by osmosis.
Water enters cells if the solution outside the cells is less concentrated than the solution inside the cells.
Water exits cells if the solution outside the cells is more concentrated than the solution inside the cells.
Prepare a table to record your results in (a)(i).
The student was given four different concentrations of sucrose solution labelled A, B, C and D.
The student was also given four potato sticks which were cut to the same length and diameter.
Step 1 The student measured the length of four potato sticks. The potato sticks for this step are shown in
Fig. 1.1.
Fig. 1.1
Step 2 The student labelled a large test-tube A and used a syringe to put 25cm3 of sucrose
solution A into the large test-tube.
Step 3 The student repeated step 2 using solutions B, C and D and three more large test tubes.
The student reused the syringe from step 2.
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Step 4 The student placed one potato stick into each of the four large test-tubes, A, B, C and D. This step
is shown in Fig. 1.2.
Fig. 1.2
Step 5 The potato sticks were left in the solutions for 30 minutes.
Step 6 After 30 minutes the student removed the potato sticks from the solutions and measured the
length of each potato stick. The potato sticks for this step are
shown in Fig. 1.3.
Fig. 1.3
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(i) Measure the length of each potato stick in Fig. 1.1 and Fig. 1.3 and record the results in your table in (a)(i).
Prepare a table to record your results in the space provided. Your table
should show:
• the length of the potato sticks at the start
• the length of the potato sticks after 30 minutes
• the change in length of the potato sticks.
[4]
(ii) Suggest why it is important to compare the change in length rather than the final lengths of the potato
sticks in this type of investigation.
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(b) The student examined each potato stick after the 30 minutes soaking time. Their observations
are recorded in Fig. 1.4.
Fig. 1.4
(i) Use the information in your table of results and in Fig. 1.2 and Fig. 1.4 to identify solutions A, B, C and D.
Write your answers in Table 1.1.
Table 1.1
relative concentration test-tube
of sucrose solution letter
least concentrated
most concentrated
[2]
(ii) Explain how the results support your answer to part (b)(i).
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(iii) Identify one source of error with the method and suggest an improvement.
error ...................................................................................................................................................................................
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improvement ......................................................................................................................................................................
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(iv) State one of the controlled variables for this investigation.
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(c) Another investigation was carried out into the effect of different concentrations of sucrose
solution on potato sticks.
In this investigation students decided to measure the change in mass rather than the change in length.
The students followed a similar method to the one in your investigation but they left the potato sticks to soak for
three hours instead of 30 minutes.
(i) Suggest why the students left the potato sticks in the solutions for three hours instead of
30 minutes.
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(ii) The students dried the potato sticks on paper towels before measuring the mass of each
potato stick.
Suggest why this step was not important in your investigation, where length was measured.
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Table 1.2 shows their results.
Table 1.2
concentration of sucrose solution /g per dm3 percentage change in mass
0 29.5
70 12.0
140 –3.0
210 –15.0
280 –26.0
350 –29.5
(iii) Using Table 1.2, plot a graph on the grid to show the effect of the concentration of
sucrose solution on the percentage change in mass.
The y-axis has been started for you.
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(iv) Use your graph to find the concentration of sucrose solution that would cause no change
in mass of the potato stick.
Mark this concentration on your graph with a + and record the concentration. Include the unit.
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(v) Students tested other potatoes and found different values for the concentration of
sucrose solution that would cause no change in mass.
Suggest one reason for this. ...........................................................................................................................................
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[Total: 24]
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2 Fig. 2.1 shows a flower. Some of the petals have been removed.
(a) Draw a large diagram of the flower.
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(b) Fig. 2.1 shows a different kind of flower.
magnification ×2.0
Fig. 2.1
(i) Measure the length of the labelled anther in the photograph.
length of anther ................................................... mm
[1]
(ii) Use your answer to 2(b)(i) and the equation to calculate the actual length of the anther.
magnification = length of anther on photograph
actual length of anther
Show your working.
actual length of anther .........................................................mm
[2]
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(c) After pollination and fertilisation, seeds will develop. These will disperse to new environments.
If conditions are suitable they will then germinate.
A student put some seeds on wet cotton wool in a Petri dish and left them to germinate. The student counted the
number of seeds that had germinated.
Describe a method the student could use to find the best or optimum temperature for the germination of seeds.
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(d) After germination, the growing seedling may get most of its energy from food stores inside the seed.
(i) Describe how you could test the food store inside the seed for starch.
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(ii) State the result that shows starch is present.
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[Total: 16]
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