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When plant cells are placed into different concentrations of sodium chloride solution, water moves between the cells and the solutions. This will affect how much a piece of plant tissue can bend.
Fig. 1.1 shows how the angle of bend of a sample of plant tissue can be measured after you have pushed it until it will bend no further without breaking.
You are provided with eight pieces of plant tissue, each soaked in a different concentration of sodium chloride solution labelled P1, P2, P3 and P4.
P1, P2 and P3 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.
P4 has an unknown concentration of sodium chloride solution.
(a) (i) When samples of the plant tissue from each of the concentrations of sodium chloride solution are put into water, water will move. Select the correct words from "least", "most", "same" to complete the sentence below. You may use a word once, more than once or not at all.
The sample of plant tissue soaked in the highest concentration of sodium chloride solution will have the ................................... bend at the start and when placed in water the bend will change the ....................................... . [1]
The size of plant tissue is a variable which needs to be considered. Each piece of plant tissue should be a standard size.
(ii) Decide how you will make sure that the pieces of plant tissue are standard size. State the size you will use.
.......................................................................................................... [1]
(iii) Describe how you will obtain accurate results to record the angle of bend of the plant samples.
.......................................................................................................... [1]
You are advised to read steps 1 to 5 before proceeding.
(iv) To observe the effect of putting samples of plant tissue from P1, P2, P3 and P4 into W for different times up to 10 minutes you need to decide the times you will use.
State the times at which you will measure the angle of bend.
.......................................................................................................... [1]
Proceed as follows:
1. Cut the pieces of plant tissue as stated in (a)(ii).
2. Measure the angle of bend of the samples of plant tissue from P1, P2, P3 and P4 as shown in Fig. 1.1. Record your results in (b)(i).
3. Put the samples from P1, P2, P3 and P4 into separate containers and add W to each container so that the samples are covered.
4. Start timing.
5. Measure the samples at each of the times that you decided in (a)(iv).
(b) (i) Prepare the space below and record your results. [7]
(ii) Use your results in (b)(i) to identify the concentrations of the sodium chloride solutions.
Complete the diagram below to show the position of each of the concentrations P1, P2 and P3. Write "P4" where it fits in the series of sodium chloride concentrations.
0.25 mol dm^-3 0.50 mol dm^-3 1.00 mol dm^-3
....... ....... ....... [2]
(iii) Explain the effect of putting the plant tissue from P1 into water, W.
.......................................................................................................... [1]
(iv) Identify two significant errors in this investigation.
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(v) A protractor was used to measure the angle of bend.
State the value of the smallest division on the protractor. ..............
State the actual error in using the protractor to measure the angle of bend.
.......................................... [1]
(vi) Suggest how you would make this investigation as reliable as possible.
.......................................................................................................... [3]
528
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516
(a) From each slide S1 and S2, make large labelled drawings of two adjacent (touching) cells and their cell contents.
Label one starch grain.
Annotate your drawings to describe one observable difference between S1 and S2.
(b) (i) Draw a large plan diagram of the tissues in the section shown in Fig. 2.2.
Label the xylem.
(ii) In Fig. 2.2 there is an outer ring of cells.
Calculate the ratio of the mean length of these cells to the mean width of these cells.
You may lose marks if you do not show your working or if you do not use appropriate units.
(c) (i) Plot a graph of the data shown in Table 2.1.
(ii) Describe the trend for the concentration of sugars in the phloem. Suggest an explanation for the trend.
513
562
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