Topic 4 Practical Skill Exam Questions

Q1.
 
(a)  It is believed that bags made from bioplastic are better for the environment because they biodegrade faster than those made from crude oil.
An investigation compared the biodegradation of bags made from bioplastic and bags made from crude oil.
Small squares of plastic were cut from the bags. They were then weighed and buried in soil. After a period of time the small squares were reweighed.
The graph below shows the results of the investigation.

(i)  Give a reason why the soil in which the plastic squares were placed needed to be kept the same.
(1)
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(ii)  State with a reason what needed to be done to the plastic squares after they had been removed from the soil for weighing.
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(b)  Analyse the data to explain the advantages of using bioplastic to make bags rather than crude oil.
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(Total for question = 5 marks)

Q2.
 
Mineral ions in the soil affect the growth of the peanut plant, Arachis hypogaea.

The effect of mineral ions on the production of fruit by these plants was investigated.
Young peanut plants were grown in soil containing all the mineral ions required.
After one week, 10 of these plants were moved into soil without calcium ions. Another 10 plants were moved into soil without magnesium ions.
Ten plants were left in the original soil.
After leaving the plants to grow, the mean number of flowers per plant and the percentage of these flowers that formed fruit were recorded.
The results are shown in the table.

(i)  Calculate the mean reduction in the number of fruit produced by peanut plants grown in soil without calcium ions.
Give your answer to two decimal places.
(3)

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(ii)  Comment on the results of this investigation.
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(Total for question = 6 marks)

Q3.
 
Seed banks store seeds to conserve different varieties of plants.
Seeds are stored for long periods of time in conditions that allow them to be germinated when required.
An investigation was carried out to study the effect of storage time on wheat seeds of two different varieties.
Wheat seeds of one variety, P, were collected and divided into six groups, each with the same number of seeds. Each group of seeds was stored in an atmosphere of 80% humidity at a temperature of 42 °C.
Each group was stored in these conditions for different lengths of time. One group of seeds was germinated immediately after collection. This was the control group.
After storage, the seeds were planted in suitable conditions to allow germination. The number of seeds that germinated was found and the mean percentage germination calculated.
This was repeated using wheat seeds of a different variety, Q.
All other variables were kept constant.
The results are shown in the table.

(i)  Describe the effect of storage time on the germination of seeds for these two varieties of wheat.
(3)
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(ii)  Explain how the results for the control were useful in this investigation.
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(Total for question = 5 marks)

Q4.
 
Many plants produce chemicals that have antimicrobial properties.
The suitability of using wood from three types of tree to make kitchen chopping boards was investigated.
In this investigation, 50 cm3 of a bacterial culture was added to 100 g of wood chippings from each of three types of tree.
The growth of bacteria was measured at the start (Day 0), and then after 1, 2, 4 and 8 days.
The results are shown in the graph.

(i)  Describe the antimicrobial properties of these three types of wood.
(2)
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(ii)  It was concluded from this investigation that spruce caused bacterial growth to decrease at a constant rate after the first day.
Criticise this conclusion.
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(iii)  Explain how this investigation could be improved to provide additional data to determine whether pine or larch have greater antimicrobial properties.
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(Total for question = 8 marks)

Q5.
 
Plant fibres and oil-based plastics have both been used to make ropes.
Climbing ropes can be made from manila (a plant fibre) or nylon (an oil-based plastic). Various factors affect the tensile strength of these ropes, including diameter and storage conditions.
The table shows the effect of rope diameter on tensile strength.

It is claimed that the ideal storage conditions for rope are 18 °C and 60% relative humidity.
Devise a valid investigation to determine the effect of storage temperature on the tensile strength of manila rope and nylon rope.
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(Total for question = 4 marks)

Q1.
No Examiner's Report available for this question

Q2.
 
(i)
This question was a good discriminator. It was, however, difficult to say whether this was based on maths ability or ability to interpret the data.
Many candidates chose to divide one percentage by the other or other seemingly random attempts at "doing something with the data", others went too far with the calculation, ending up with a percentage decrease.
Those who followed the correct process stood out.

Results Plus: Examiner Comments
Although this candidate did not receive full marks, it is a good example of how to set out a response.

Results Plus: Examiner Tip
Calculations can become confused − label each step for clarity

Results Plus: Examiner Comments
This response explains exactly how the calculation is progressing and highlights perfectly where marks should be awarded.

(ii)
The candidates were asked to comment on the data which seemed to be misinterpreted by some. Those that identified the idea of deficiency were able to score well. Many candidates reverted to quoting the data, referring to containing all minerals being the highest.

Q3.
 
(i)
In this question item, candidates were expected to use the data table to describe the effect of storage time on germination success for wheat varieties P and Q.
A pleasing majority of candidates were able to recognise the reduction in successful germination of both varieties as storage time increased. However, many then simply repeated the data that was presented rather than manipulating it or giving subtrends as described by the third and fourth marking points.
The candidate has given an appropriate overall description of the trend. As the question referred to both varieties of wheat, the trend must apply to both for the award of this mark. However, the candidate does not then either manipulate the data or describe any subtrends.

Results Plus: Examiner Comments
Only the first marking point can be awarded so 1/3.

Results Plus: Examiner Tip
If data is going to be used in an answer, consider whether it should be manipulated in some way. 

In this case, as both varieties are involved, one manipulation per variety was required for the second marking point.

(ii)
In this item, candidates were required to explain how the results of the control were useful in the context of the investigation described in this question.
Whilst all marking points were seen, the first marking point was the most commonly encountered one, with the final marking point being the second most common. It should be noted that many candidates gave generic responses that did not relate to the context provided. This is illustrated in the two examples provided.
In this response, the candidate has only shown that they recognise that the control can be used as a comparison but has not really stated what the comparison is between.

Results Plus: Examiner Comments
No marks were achieved.

This candidate has shown that the control will have a comparison function but has not linked this to both varieties of wheat, nor to being stored.

Results Plus: Examiner Comments
No marks were awarded.

 

Q4.
 
(i)
Most responses focussed on spruce being less effective than pine or larch. Few found it worthy of note that pine and larch seemed to have equal properties. A few candidates misinterpreted the data and rated spruce as the highest antimicrobial properties as growth continued to fall throughout the experiment.
(ii)
Candidates who appreciated the non-linear time scale were able to pick up marks here. Many candidates ignored the data and instead gave general responses about lack of repeats, lack of information regarding sample size or an explanation of how variables were controlled.
(iii)
This question was well answered by A grade candidates although few marks were awarded to many candidates. Although asked for improvements, too many responses described a different investigation based on measuring zones of inhibition.
There were few responses seen that explained the reason for their suggested improvement.

Results Plus: Examiner Comments
This response gains no marks as it refers to making the results more reliable. The question asks to provide additional data.

 

Q5.
 
This question required the design of a valid investigation to determine the effect of storage temperature on tensile strength of rope.
There were many good, well thought out investigations that considered all aspects, including the independent and dependent variables. However, some candidates did not take into account the word 'storage' and described carrying out the experiment in different temperatures. Many varied both temperature and humidity, rather than picking out that the humidity should be controlled and kept at 60%. Many candidates gave an appropriate range of temperatures, either side of 18°C, but a few did not go above 18°C. Some students referred to keeping the fibres in a water bath; whilst this was not penalised in this question, students should be reminded to think of investigations from a practical viewpoint and make sure that the method they describe is realistic.
Many candidates considered controlled variables and referred to keeping the diameter of the rope the same but did not refer to the length. Meanwhile, some referred to using the same species of nylon rope!
It was evident from the answers seen which candidates had taken an active part in the core practical concerning testing of tensile strength. It is imperative that students do carry out the core practicals.

Results Plus: Examiner Comments
This response was given 3/4 marks. Marks were given for:

  •  a range of temperatures above and below 18°C; 
  •  ropes kept at the different temperatures for 24 hours; 
  •  masses added until rope broke.

Results Plus: Examiner Tip
No mark for fibres being of the same diameter without mention of same length.

Results Plus: Examiner Comments
This response was given 4/4 marks. Marks were given in the following sequence:

  •  range of temperatures from 10 – 20°C; 
  •  humidity of 60% in storage area; 
  •  masses added until fibre broke; 
  •  controlled variables described as diameter and length of fibre.

Results Plus: Examiner Tip
A diagram can help make it clear what is being described and can also help the candidate to visualise the practical procedure, making it easier to then describe in words.

 

Mark Scheme

Q1.

Q2.

 

Q3.

 

Q4.

 

Q5.