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Cambridge IGCSE Biology practice

Paper 6 structured question: Osmosis

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Osmosis

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Paper 6Alternative to PracticalPractical4 marks

Investigating osmosis in plant tissues using different solution concentrations.

Results Table

Results of Osmosis Experiment

Potato cylinders were placed in solutions of varying sucrose concentration for 30 minutes. The percentage change in mass was recorded.

Sucrose concentration (%)Percentage change in mass (%)
012
56
100
15-6
20-12
  1. a

    Suggest why the percentage change in mass is zero at 10% sucrose concentration.

    Aim for approximately 2 distinct marking points.

    [2]
  2. b

    Plan an improvement to increase the accuracy of this osmosis investigation.

    Aim for approximately 2 distinct marking points.

    [2]

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Paper 6 structured question: Osmosis

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Method

Method for Investigating Osmosis in Potato Cylinders

1. Cut potato cylinders of equal size. 2. Measure and record the initial mass of each cylinder. 3. Place each cylinder in a different sucrose solution concentration (0%, 5%, 10%, 15%, 20%) for 30 minutes. 4. Remove cylinders, blot dry, and measure the final mass. 5. Calculate the percentage change in mass for each cylinder.

Solution concentration (%)Initial mass (g)Final mass (g)Percentage change in mass (%)
02.002.2010
52.002.105
102.002.000
152.001.90-5
202.001.80-10
  1. a

    Identify the independent variable in this investigation.

    Aim for approximately 1 distinct marking point.

    [1]
  2. b

    Describe how the percentage change in mass is calculated.

    Aim for approximately 2 distinct marking points.

    [2]
  3. c

    Explain why the potato cylinders lost mass in the 15% and 20% sucrose solutions.

    Aim for approximately 3 distinct marking points.

    [3]