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(a) State the hazard with the greatest level of risk when using the apparatus and solutions and state the level of risk of the procedure: low or medium or high.
hazard ......................................................................................................................................................
level of risk ........................................................................................................................................................[1]
(b) (i) Decide which concentrations of sodium chloride solution to prepare:
using simple dilution
using 10% sodium chloride solution, S.
Complete the table to show how you will prepare these concentrations.
[Table 1.1]
During the investigation you will mix 10 cm³ of each concentration of sodium chloride solution with 10 cm³ of yeast cell suspension to make a mixture, SY.
This will result in the concentration of the sodium chloride solution in SY being halved as shown in Table 1.2.
[Table 1.2]
(ii) Prepare the space below to record your raw results and your processed results.
[6]
(iii) Explain why it is necessary to collect a result for the 0% sodium chloride solution and yeast mixture, SY.
.................................................................................................................................................................
.................................................................................................................................................................[1]
(iv) State the value of the smallest division on the scale of your thermometer.
smallest division ........................ °C
State the actual error in measuring an increase in temperature of 6°C using this thermometer.
actual error 6°C ± .............................. [1]
(v) The actual error of using the thermometer is the same for each measurement. The trend in the results is not affected and it is not a significant source of error.
Due to the procedure, the highest temperature recorded may be inaccurate (not close to the true temperature).
Suggest how step 9 and step 11 (on page 4) introduced an error which caused the highest temperature recorded to be inaccurate.
.................................................................................................................................................................
.................................................................................................................................................................[1]
(vi) This procedure investigated the effect of the concentration of sodium chloride solution on the activity of catalase in yeast cells.
To modify this procedure for investigating another variable, the independent variable (concentration of sodium chloride) would need to be standardised.
Describe how the independent variable (concentration of sodium chloride solution) will be standardised.
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Consider how you would modify this procedure to investigate the effect of the concentration of hydrogen peroxide on the activity of the catalase in yeast cells.
Describe how the independent variable (concentration of hydrogen peroxide) will be investigated.
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.................................................................................................................................................................[3]
(c) In a similar investigation, a student investigated how changing the concentration of copper sulfate solution (independent variable) affected the hydrolysis of hydrogen peroxide.
The release of oxygen was measured by counting the bubbles when the oxygen was released through a delivery tube into a test-tube of water.
The results are shown in Table 1.3.
[Table 1.3]
You are required to use a sharp pencil for graphs.
(i) Plot a graph of the data shown in Table 1.3.
[4]
(ii) Explain the relationship between the concentration of copper sulfate solution and the activity of the catalase.
.................................................................................................................................................................
.................................................................................................................................................................[2]
517
600
546
(a) K1 is a slide of a stained transverse section through a plant stem.
You are not expected to be familiar with this specimen.
An eyepiece graticule scale can be used to measure the layers of tissues and to help draw a plan diagram with the correct shape and proportions of the tissues, without needing to calibrate the eyepiece graticule scale.
You are required to use a sharp pencil for drawings.
(i) Select one vascular bundle from one of the corners of the specimen on K1.
The grid and your eyepiece graticule should help you draw the vascular bundle with the correct shape and proportions of the tissues.
Draw on the grid below a large plan diagram of the vascular bundle you have selected.
Use one ruled label line and label to identify the xylem.
(ii) Observe the tissue (cortex) between the epidermis and the vascular bundle.
Select one group of four cells made up of:
• two cells from the epidermis
• two cortex cells which touch each other and at least one of the epidermis 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.
(b) Fig. 2.1 is a photomicrograph of a stained transverse section of a stem of a different plant species.
(i) Calculate the actual length of the line A shown on Fig. 2.1.
You may lose marks if you do not show your working.
actual length .......................... μm
(ii) A student observed a different plant of the same species shown in Fig. 2.1. The student determined the ratio of the radius of the stem to the length of one air space as 266:82.
However, a ratio may be simplified to the smallest possible whole number on each side.
In this example, both sides of the ratio 266:82 are divisible by 2, so the simplest ratio for the measurements taken by the student is 133:41.
The actual radius of the stem in Fig. 2.1 is 825 μm.
Determine the simplest ratio of the radius of the stem in Fig. 2.1 to the length of an air space (line A).
ratio ........................................
(iii) Suggest a habitat where this plant might grow and one observable feature shown in Fig. 2.1, which enables it to live in this habitat.
habitat ..........................................................................................
feature .........................................................................................
(c) Prepare the space below so that it is suitable for you to record observable differences between the specimen on K1 and Fig. 2.1.
Record your observations in the space you have prepared.
520
548
580
