AS & A Level Biology - 9700 Paper 3 2016 Winter Zone 4

You are provided with four different concentrations of sodium chloride solution labelled S1, S2, S3 and S4. Each concentration of sodium chloride solution contains two pieces of potato.

S1, S2 and S3 each contain one of the concentrations of sodium chloride solution, 1.00 mol dm^-3, 0.50 mol dm^-3 and 0.25 mol dm^-3 but not necessarily in that order.

S4 has an unknown concentration of sodium chloride solution.

(a)

(i) Complete the sentence by selecting the correct word from: least or most or same.

The piece of potato soaked in the lowest concentration of sodium chloride solution
will have the .................................. angle of bend when compared to the other
concentrations of sodium chloride solution.
[1]

You are required to:
• measure the angle of bend for each of the pieces of potato from S1, S2 and S3
• use these results to identify the concentrations of the sodium chloride solutions, S1, S2 and S3.

The size of the pieces of potato is a variable which needs to be standardised.

(ii) Decide how you will make sure that the pieces of potato are a standard size.
State the size you will use.
............................................................................................................................................
............................................................................................................................................
[1]

(iii) Describe how you will obtain accurate results to record the angle of bend.
............................................................................................................................................
............................................................................................................................................
[1]

Proceed as follows:

1. Cut the pieces of potato as stated in (a)(ii) and return to the appropriate solution.
2. Before measuring the angle of bend, remove excess liquid from the piece of potato using the paper towel.
3. Measure the angle of bend of the pieces of potato from S1, S2 and S3 using the Method of measuring the angle of bend as described on page 3.

Note: before measuring, remove excess liquid from the piece of potato and make sure the plastic covering on the page of protractors is dry.

4. Record your results in (a)(iv).

(iv) Prepare the space below and record your results.
[5]

(v) Using your results in (a)(iv) state the concentration of sodium chloride solution in S1, S2 and S3.

S1 ................. mol dm^-3
S2 ................. mol dm^-3
S3 ................. mol dm^-3
[1]

5. Repeat step 3 using the pieces of potato from S4 and record your result in (a)(vi).

(vi) Record the angle of bend for the pieces of potato from S4.
............................................................................................................................................
............................................................................................................................................
[1]

(vii) Estimate the concentration of the sodium chloride solution in S4 using your results in (a)(iv), (a)(v) and (a)(vi).
............................................................................................................................................
............................................................................................................................................
[1]

You are expected to use a sharp pencil to draw graphs.

A student recorded angles of bend of 0° for pure water (0 mol dm^-3 sodium chloride solution) and 2° for 0.15 mol dm^-3 sodium chloride solution.

(viii) Plot a graph to show the relationship between the concentration of sodium chloride solution and the angle of bend using:
• the results recorded by the student
• your results as recorded in (a)(iv)
• the concentrations of sodium chloride solution stated in (a)(v).

[3]

(ix) A more accurate estimate for the concentration of sodium chloride solution in S4 can be found by using this graph.

Use your graph to estimate the concentration of sodium chloride solution in S4 using your answer to (a)(vi).
Show on the graph how you estimated the concentration of sodium chloride solution.

concentration in S4 ................................................
[2]

(b) Suggest how you would improve this procedure to have more confidence in your estimate of S4.
............................................................................................................................................
............................................................................................................................................
............................................................................................................................................
[3]

(c) A student puts a piece of the potato from S1 into water. Explain, in terms of water potential, the effect this would have on the potato cells.
............................................................................................................................................
............................................................................................................................................
[2]

You are provided with four different concentrations of sodium chloride solution labelled S1, S2, S3 and S4. Each concentration of sodium chloride solution contains two pieces of potato.

S1, S2 and S3 each contain one of the concentrations of sodium chloride solution, 1.00 mol dm^-3, 0.50 mol dm^-3 and 0.25 mol dm^-3 but not necessarily in that order.

S4 has an unknown concentration of sodium chloride solution.

(a)

(i) Complete the sentence by selecting the correct word from: least or most or same.

The piece of potato soaked in the lowest concentration of sodium chloride solution
will have the .................................. angle of bend when compared to the other
concentrations of sodium chloride solution.
[1]

You are required to:
• measure the angle of bend for each of the pieces of potato from S1, S2 and S3
• use these results to identify the concentrations of the sodium chloride solutions, S1, S2 and S3.

The size of the pieces of potato is a variable which needs to be standardised.

(ii) Decide how you will make sure that the pieces of potato are a standard size.
State the size you will use.
............................................................................................................................................
............................................................................................................................................
[1]

(iii) Describe how you will obtain accurate results to record the angle of bend.
............................................................................................................................................
............................................................................................................................................
[1]

Proceed as follows:

1. Cut the pieces of potato as stated in (a)(ii) and return to the appropriate solution.
2. Before measuring the angle of bend, remove excess liquid from the piece of potato using the paper towel.
3. Measure the angle of bend of the pieces of potato from S1, S2 and S3 using the Method of measuring the angle of bend as described on page 3.

Note: before measuring, remove excess liquid from the piece of potato and make sure the plastic covering on the page of protractors is dry.

4. Record your results in (a)(iv).

(iv) Prepare the space below and record your results.
[5]

(v) Using your results in (a)(iv) state the concentration of sodium chloride solution in S1, S2 and S3.

S1 ................. mol dm^-3
S2 ................. mol dm^-3
S3 ................. mol dm^-3
[1]

5. Repeat step 3 using the pieces of potato from S4 and record your result in (a)(vi).

(vi) Record the angle of bend for the pieces of potato from S4.
............................................................................................................................................
............................................................................................................................................
[1]

(vii) Estimate the concentration of the sodium chloride solution in S4 using your results in (a)(iv), (a)(v) and (a)(vi).
............................................................................................................................................
............................................................................................................................................
[1]

You are expected to use a sharp pencil to draw graphs.

A student recorded angles of bend of 0° for pure water (0 mol dm^-3 sodium chloride solution) and 2° for 0.15 mol dm^-3 sodium chloride solution.

(viii) Plot a graph to show the relationship between the concentration of sodium chloride solution and the angle of bend using:
• the results recorded by the student
• your results as recorded in (a)(iv)
• the concentrations of sodium chloride solution stated in (a)(v).

[3]

(ix) A more accurate estimate for the concentration of sodium chloride solution in S4 can be found by using this graph.

Use your graph to estimate the concentration of sodium chloride solution in S4 using your answer to (a)(vi).
Show on the graph how you estimated the concentration of sodium chloride solution.

concentration in S4 ................................................
[2]

(b) Suggest how you would improve this procedure to have more confidence in your estimate of S4.
............................................................................................................................................
............................................................................................................................................
............................................................................................................................................
[3]

(c) A student puts a piece of the potato from S1 into water. Explain, in terms of water potential, the effect this would have on the potato cells.
............................................................................................................................................
............................................................................................................................................
[2]

L1 is a slide of a stained transverse section through a plant leaf. You are not expected to be familiar with this specimen.

(a) Select a field of view so that you can observe the part of the leaf shown by the shaded area in Fig. 2.1.
You are required to use a sharp pencil for drawings.
(i) Draw a large plan diagram of the part of the leaf observed in the field of view. Use one ruled label line and label to identify one layer of epidermis.



Figure 2.1
You are expected to draw the correct shape and proportions of the different tissues.

(ii) Observe the cells in the ring around the vascular bundle on L1. These cells are not identical. Select one group of four adjacent (touching) cells which show some of the differences between these cells. Each cell of the group must touch at least one of the other cells. Make a large drawing of this group of four cells. Use one ruled label line and label to identify the cell wall of one cell. [6]

(b) (ii) Using the actual thicknesses calculated in (b)(i), calculate the mean actual thickness of the leaf. You may lose marks if you do not show your working or if you do not use appropriate units.

mean actual thickness ......................................................... [2]

(c) The leaf on slide L1 and the leaf in Fig 2.2 are adapted to living in dry conditions. Prepare the space below so that it is suitable for you to record observable differences in xerophytic adaptations between these two specimens. Record your observations in the space you have prepared. [3]

L1 is a slide of a stained transverse section through a plant leaf. You are not expected to be familiar with this specimen.

(a) Select a field of view so that you can observe the part of the leaf shown by the shaded area in Fig. 2.1.
You are required to use a sharp pencil for drawings.
(i) Draw a large plan diagram of the part of the leaf observed in the field of view. Use one ruled label line and label to identify one layer of epidermis.



Figure 2.1
You are expected to draw the correct shape and proportions of the different tissues.

(ii) Observe the cells in the ring around the vascular bundle on L1. These cells are not identical. Select one group of four adjacent (touching) cells which show some of the differences between these cells. Each cell of the group must touch at least one of the other cells. Make a large drawing of this group of four cells. Use one ruled label line and label to identify the cell wall of one cell. [6]

(b) (ii) Using the actual thicknesses calculated in (b)(i), calculate the mean actual thickness of the leaf. You may lose marks if you do not show your working or if you do not use appropriate units.

mean actual thickness ......................................................... [2]

(c) The leaf on slide L1 and the leaf in Fig 2.2 are adapted to living in dry conditions. Prepare the space below so that it is suitable for you to record observable differences in xerophytic adaptations between these two specimens. Record your observations in the space you have prepared. [3]