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You are required to investigate the effect of different surface areas (independent variable) on the release of methylene blue from pieces of stained plant tissue.
You are provided with:
[Table_1]
If any methylene blue comes into contact with your skin wash off immediately with water.
It is recommended that you wear safety glasses/goggles.
When carrying out a practical procedure, the hazards of the use of all the apparatus and solutions need to be considered. Then the level of risk needs to be assessed as low or medium or high.
(a) State the hazard with the greatest level of risk when carrying out step 1 on page 4.
State the level of risk of the procedure: low or medium or high.
hazard ..........................................................................................................................
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level of risk ...................................................................................................................... [1]
(b) Each piece of plant tissue has the same cross-sectional area. The largest piece needs to be cut to a length of $4\text{cm}$ by removing each end.
(i) Complete Fig. 1.1 to show how you will cut further pieces which reduce the length by half between each piece of plant tissue. Fig. 1.1 is not drawn to scale.
(ii) Complete the table to show for each piece in (b)(i):
\(\bullet\) the dimensions of the piece of plant tissue
\(\bullet\) the surface area of each piece.
[Table_2]
(iii) Describe how you will standardise the volume of \(S\) for each piece of plant tissue.
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(iv) Prepare the space below and record your results. [6]
(v) A student suggested:
'The ruler used to measure the pieces of plant tissue resulted in both systematic error and random error.'
State which type of error, systematic or random, could affect the trend in the results. Give a reason for your answer.
type of error ................................................................................................................
reason ....................................................................................................................... [2]
(vi) Explain how the methylene blue solution was released from the stained plant tissue.
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......................................................................................................................... [1]
(vii) This procedure investigated the effect of different surface areas of stained plant tissue when placed into a salt solution.
To modify this procedure for investigating another variable, the independent variable (surface area) would need to be standardised.
Describe how the independent variable (surface area) would be standardised.
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Consider how you would modify this procedure to investigate the effect of temperature on the stained plant tissue.
Describe how the independent variable, \textbf{temperature}, will be investigated.
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......................................................................................................................... [3]
500
520
600
8. View the slide to observe the starch grains using the microscope. Select an area of starch grains on the slide.
You may need to reduce the amount of light entering the microscope to observe cells clearly.
You must adjust the fine focus to observe the patterns in the starch grains.
You are required to use a sharp pencil for drawings.
(a) Select 6 starch grains which show the different sizes and features of the grains.
(i) Make a large drawing of these 6 starch grains.
(ii) Use Fig. 2.1 to suggest which of the starch grains, J, K, L or M matches some of the grains observed on the slide.
answer ...............................................................[1]
9. Remove the slide from the microscope and place it on a paper towel.
You will now add solution I to the water on the slide without removing the coverslip.
10. Put a drop of solution I onto the slide so that the drop touches the edge of the coverslip. Wait a few seconds while the solution I moves under the coverslip. Use the paper towel to remove any excess liquid from the top of the coverslip.
11. Immediately use the microscope to observe the starch grains where there is solution I on the slide.
(iii) Suggest why using solution I as a stain may lead to inaccurate recording of the features of starch grains.
........................................................ [1]
(b) Scientists investigated the mean size of starch grains in cells from five different types of maize D, E, F, G and H.
The results are shown in Table 2.1.
[Table_2.1]
(i) Circle the anomalous result in Table 2.1. [1]
(ii) Complete the table by calculating the missing mean value. [1]
You are required to use a sharp pencil for charts.
(iii) Plot a chart of the data in Table 2.1.
Note: To plot the data clearly, the scale should not have 0 at the origin.
[Grid_Image]
[4]
(iv) Suggest one reason which might explain the differences in the mean size of starch grains between different types of maize.
.......................................................................[1]
(c) A student calibrated the eyepiece graticule in a light microscope using a stage micrometer scale so that they could find the actual length of specimens observed using a light microscope.
The calibration was: one eyepiece graticule division equal to 0.023 mm.
The use of this unit (mm) is not the most appropriate unit for use with a light microscope.
(i) State which unit is the most appropriate for use with a light microscope and show how the value 0.023 mm is converted to this unit.
You may lose marks if you do not show your working.
(d) Draw a large plan diagram of the sector as shown on Fig. 2.3.
You are not expected to be familiar with this specimen.
Use one ruled label line and label to identify the vascular bundle.
510
518
538
