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(a) A student investigated the effect of the concentration of ethanol on the cloudiness of the emulsion during the emulsion test.
The student suggested the following hypothesis:
lowering the concentration of ethanol below 100% will have no effect on the cloudiness of the emulsion.
You will need to investigate this hypothesis by:
- diluting 100% ethanol, A, to provide further concentrations of ethanol
- carrying out the emulsion test using these concentrations of ethanol
- recording the cloudiness of the emulsion formed.
[Table_1]
If A comes into contact with your skin, wash off immediately under cold water.
It is recommended that you wear suitable eye protection.
You will need to use simple (proportional) dilution of the ethanol, A, to make further concentrations of ethanol between 100% and 75%, by reducing each successive dilution by 5%.
You need to prepare 10 cm3 of each concentration.
Table 1.2 shows how to prepare the highest concentration (100%) and the lowest concentration (75%).
(i) Complete Table 1.2 to show how you will prepare further concentrations of ethanol.
[Table_2]
(ii) Record your results in an appropriate table, including the mean result for each concentration of ethanol.
(iii) State the independent variable in the investigation you have just carried out.
$\text{........................................................................................................................... [1]}$
(iv) Identify one significant source of error when measuring the dependent variable and
suggest one improvement to reduce this source of error.
$\text{source of error .......................................................................................................}$
$\text{..........................................................................................................................}$
$\text{improvement ........................................................................................................}$
$\text{..........................................................................................................................}$
(v) The student’s hypothesis stated that:
lowering the concentration of ethanol below 100% will have no effect on the cloudiness of the emulsion.
State whether you support or reject this hypothesis.
Explain how your results provide evidence for this decision.
$\text{support or reject ...........................................................................................}$
$\text{explanation ....................................................................................................}$
$\text{..........................................................................................................................}$
(vi) In the test-tubes the layer above the emulsion consists of undissolved lipids.
Suggest how the student could find the volume of ethanol required to dissolve all the lipid in L.
$\text{..........................................................................................................................}$
$\text{..........................................................................................................................}$
$\text{..........................................................................................................................}$
(b) Some foods contain two types of fat, unsaturated fat (U) and saturated fat (S). The proportions of these two types of fat vary according to the food.
A scientist carried out some tests to determine the mass of these two types of fat found in three food samples, X, Y and Z. The total mass of each food sample was 100 g.
The results are shown in Table 1.3.
[Table_3]
(i) Calculate the percentage of the total fat in food sample X that is unsaturated.
Show all the steps in your working and use appropriate units.
(ii) Draw a bar chart of the data shown in Table 1.3 on the grid in Fig. 1.3.
The bars should be separated for each food sample.
Use a sharp pencil for drawing bar charts.
[Fig_1.3]
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(a) A student investigated the effect of the concentration of ethanol on the cloudiness of the emulsion during the emulsion test.
The student suggested the following hypothesis:
lowering the concentration of ethanol below 100% will have no effect on the cloudiness of the emulsion.
You will need to investigate this hypothesis by:
- diluting 100% ethanol, A, to provide further concentrations of ethanol
- carrying out the emulsion test using these concentrations of ethanol
- recording the cloudiness of the emulsion formed.
[Table_1]
If A comes into contact with your skin, wash off immediately under cold water.
It is recommended that you wear suitable eye protection.
You will need to use simple (proportional) dilution of the ethanol, A, to make further concentrations of ethanol between 100% and 75%, by reducing each successive dilution by 5%.
You need to prepare 10 cm3 of each concentration.
Table 1.2 shows how to prepare the highest concentration (100%) and the lowest concentration (75%).
(i) Complete Table 1.2 to show how you will prepare further concentrations of ethanol.
[Table_2]
(ii) Record your results in an appropriate table, including the mean result for each concentration of ethanol.
(iii) State the independent variable in the investigation you have just carried out.
$\text{........................................................................................................................... [1]}$
(iv) Identify one significant source of error when measuring the dependent variable and
suggest one improvement to reduce this source of error.
$\text{source of error .......................................................................................................}$
$\text{..........................................................................................................................}$
$\text{improvement ........................................................................................................}$
$\text{..........................................................................................................................}$
(v) The student’s hypothesis stated that:
lowering the concentration of ethanol below 100% will have no effect on the cloudiness of the emulsion.
State whether you support or reject this hypothesis.
Explain how your results provide evidence for this decision.
$\text{support or reject ...........................................................................................}$
$\text{explanation ....................................................................................................}$
$\text{..........................................................................................................................}$
(vi) In the test-tubes the layer above the emulsion consists of undissolved lipids.
Suggest how the student could find the volume of ethanol required to dissolve all the lipid in L.
$\text{..........................................................................................................................}$
$\text{..........................................................................................................................}$
$\text{..........................................................................................................................}$
(b) Some foods contain two types of fat, unsaturated fat (U) and saturated fat (S). The proportions of these two types of fat vary according to the food.
A scientist carried out some tests to determine the mass of these two types of fat found in three food samples, X, Y and Z. The total mass of each food sample was 100 g.
The results are shown in Table 1.3.
[Table_3]
(i) Calculate the percentage of the total fat in food sample X that is unsaturated.
Show all the steps in your working and use appropriate units.
(ii) Draw a bar chart of the data shown in Table 1.3 on the grid in Fig. 1.3.
The bars should be separated for each food sample.
Use a sharp pencil for drawing bar charts.
[Fig_1.3]
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503
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(a) N1 is a slide of a stained transverse section through a leaf-like structure. You are not expected to be familiar with this specimen.
Use a sharp pencil for drawing.
(i) Select a field of view so that you can observe the different tissues shown by the shaded area in Fig. 2.1.
Draw a large plan diagram from the selected field of view which has:
• part of the epidermis
• the outline of \textit{two} vascular bundles
• any other observable tissues.
No details of the internal tissues of the vascular bundles are required.
Use \textit{one} ruled label line and the label \textbf{C} to identify the tissue containing chloroplasts.
You are expected to draw the correct shape and proportions of the different tissues.
(ii) Observe the \textit{largest} vascular bundle on N1.
Select \textit{one} group of \textbf{four} adjacent, touching xylem vessel elements. Each xylem vessel element must touch at least one of the other xylem vessel elements.
Make a large drawing of this group of \textbf{four} xylem vessel elements.
Use \textit{one} ruled label line and label to identify the lumen of \textit{one} xylem vessel element.
You are expected to draw the correct shape and proportions of the different cells.
(iii) On your drawing in (a)(ii), use \textit{one} ruled label line and the label \textbf{T} to identify an observable feature which enables water to be transported through the xylem vessel element.
Next to the letter \textbf{T} explain how this feature enables the xylem vessel element to carry out its function.
(b) Fig. 2.2 is a photomicrograph of a stained transverse section through the trachea of a mammal.
(i) On Fig. 2.2, use \textit{one} ruled label line and the label \textbf{Q} to identify an observable feature which prevents the tube from collapsing. [1]
(ii) Determine the simplest whole number ratio of the length of \textbf{P3} (the air space) to the total length of \textbf{P1} and \textbf{P2}.
Show all the steps in your working and use appropriate units. [5]
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(a) N1 is a slide of a stained transverse section through a leaf-like structure. You are not expected to be familiar with this specimen.
Use a sharp pencil for drawing.
(i) Select a field of view so that you can observe the different tissues shown by the shaded area in Fig. 2.1.
Draw a large plan diagram from the selected field of view which has:
• part of the epidermis
• the outline of \textit{two} vascular bundles
• any other observable tissues.
No details of the internal tissues of the vascular bundles are required.
Use \textit{one} ruled label line and the label \textbf{C} to identify the tissue containing chloroplasts.
You are expected to draw the correct shape and proportions of the different tissues.
(ii) Observe the \textit{largest} vascular bundle on N1.
Select \textit{one} group of \textbf{four} adjacent, touching xylem vessel elements. Each xylem vessel element must touch at least one of the other xylem vessel elements.
Make a large drawing of this group of \textbf{four} xylem vessel elements.
Use \textit{one} ruled label line and label to identify the lumen of \textit{one} xylem vessel element.
You are expected to draw the correct shape and proportions of the different cells.
(iii) On your drawing in (a)(ii), use \textit{one} ruled label line and the label \textbf{T} to identify an observable feature which enables water to be transported through the xylem vessel element.
Next to the letter \textbf{T} explain how this feature enables the xylem vessel element to carry out its function.
(b) Fig. 2.2 is a photomicrograph of a stained transverse section through the trachea of a mammal.
(i) On Fig. 2.2, use \textit{one} ruled label line and the label \textbf{Q} to identify an observable feature which prevents the tube from collapsing. [1]
(ii) Determine the simplest whole number ratio of the length of \textbf{P3} (the air space) to the total length of \textbf{P1} and \textbf{P2}.
Show all the steps in your working and use appropriate units. [5]
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