Required practicals practice paper: Methods, variables, results and evaluation — question paper

Section A: Multiple-choice questions[10 marks]

Choose one answer for each question. Each question is worth 1 mark.

1. 1

   In the microscopy practical, a cover slip is lowered slowly at an angle to

   1. Aavoid trapping air bubbles
   2. Bkill the cells
   3. Cadd the stain
   4. Dfocus the image
   ( )
2. 2

   In the osmosis practical, percentage change in mass is calculated because

   1. Ait removes all units
   2. Bit is faster to work out
   3. Cthe potato chips start at different masses
   4. Dbalances are unreliable
   ( )
3. 3

   Benedict's solution, heated with a food sample, turns brick-red when

   1. Astarch is present
   2. Ba reducing sugar is present
   3. Cprotein is present
   4. Dfat is present
   ( )
4. 4

   In the amylase practical, iodine is used to

   1. Astain the enzyme
   2. Btest for protein
   3. Cfeed the starch
   4. Dtest whether starch remains
   ( )
5. 5

   In the pondweed practical, the rate of photosynthesis is measured by

   1. Acounting the leaves
   2. Bcounting oxygen bubbles per minute
   3. Cweighing the plant
   4. Dtiming a colour change
   ( )
6. 6

   In the ruler-drop test of reaction time, a longer falling distance means a

   1. Afaster reaction
   2. Bmore concentrated person
   3. Cslower reaction
   4. Dlonger ruler
   ( )
7. 7

   Quadrats are placed at random positions in a field to

   1. Asave time
   2. Bprotect the plants
   3. Cincrease the count
   4. Davoid sampling bias
   ( )
8. 8

   In the decay practical, the rate of decay is followed by

   1. Atiming an indicator colour change
   2. Bcounting oxygen bubbles
   3. Cweighing a plant
   4. Dreading a thermometer
   ( )
9. 9

   Which factor does NOT affect the rate of decay of food material?

   1. Atemperature
   2. Bthe colour of light hitting it
   3. Coxygen availability
   4. Dwater availability
   ( )
10. 10

    A transect is used to show how the distribution of organisms changes

    1. Aover several years
    2. Binside a single quadrat
    3. Calong a line across a habitat
    4. Dbetween two countries
    ( )

Section B: Structured questions[50 marks]

Answer all questions in the spaces provided.

1. 11

   This question is about the microscopy required practical.

   1. (a)

      Put these steps in order: focus with the coarse adjustment; stain the specimen and lower the cover slip; switch to a higher objective lens; cut a very thin piece of the specimen and place it on a slide in a drop of water; focus with the fine adjustment.

      [4]
   2. (b)

      A cell seen down the microscope is 6 mm wide. Its real width is 0.02 mm. Calculate the magnification.

      [3]
   3. (c)

      Explain why the specimen must be cut thin and why a stain is used.

      [3]
2. 12

   This question is about the osmosis required practical.

   1. (a)

      A student investigates osmosis in potato chips. Describe the method, naming two variables that must be controlled.

      [4]
   2. (b)

      A chip with a starting mass of 2.5 g has a final mass of 3.0 g. Calculate the percentage change in mass.

      [3]
   3. (c)

      Explain how a graph of the results is used to find the concentration of the cell sap.

      [3]
3. 13

   This question is about the food tests and the enzyme practical.

   1. (a)

      Describe the test for starch and its positive result.

      [3]
   2. (b)

      Describe the test for protein and its positive result.

      [3]
   3. (c)

      Describe how a student investigates the effect of pH on amylase, and how the results identify the optimum pH.

      [4]
4. 14

   This question is about the photosynthesis and reaction-time practicals.

   1. (a)

      A student moves a lamp closer to pondweed to investigate light intensity. State the independent variable, the dependent variable and two variables that must be controlled.

      [4]
   2. (b)

      When the lamp is 20 cm away the plant releases 10 bubbles per minute; at 10 cm it releases 40 bubbles per minute. Explain why the rate rises more than double when the distance is halved.

      [3]
   3. (c)

      In the reaction-time practical, state two variables to control and explain why repeats improve the result.

      [3]
5. 15

   This question is about the quadrat and decay practicals.

   1. (a)

      A field of 2 000 m² is sampled with 1 m² quadrats. The ten quadrat counts of daisies are 4, 7, 5, 6, 5, 8, 6, 4, 5 and 5. Estimate the total daisy population of the field.

      [4]
   2. (b)

      In a decay practical, a tube of fresh milk, sodium carbonate and phenolphthalein with added lipase turns colourless after 60 minutes at 20 °C and after 20 minutes at 40 °C. Compare the rates and explain the difference.

      [3]
   3. (c)

      Explain why quadrat positions are chosen randomly and how the reliability of the estimate could be improved.

      [3]