# Practical questions

You will complete 21 required practical activities if you are studying GCSE combined science: Synergy. You could be asked questions about the apparatus, methods, safety precautions, results, analysis and evaluation of these experiments.

There will be a number of different types of practical based questions. Some will be on the set required practicals, some will cover the working scientifically terms and some will be on other science practicals which you might have done in class. Use all the information given in the question particularly any diagrams to help you understand what the question is about.

This page contains AQA material which is reproduced by permission of AQA.

## Sample question 1 - Foundation

Question

A student investigated the number of ribwort plants in a field.

The student used a quadrat and a 100 metre tape measure.

This is the method used.

1. Place the quadrat in an area where there are lots of ribwort plants in the field.
2. Count the number of ribwort plants inside a quadrat.
3. Repeat steps 1 and 2 four more times.

How could the student improve his method so that he can collect valid results?

Tick two boxes. [2 marks]

 Count the leaves of each ribwort plant Place more quadrats in the field Place the quadrats randomly Use a smaller quadrat Weigh the ribwort plants
 Count the leaves of each ribwort plant Place more quadrats in the field ✔ Place the quadrats randomly ✔ Use a smaller quadrat Weigh the ribwort plants

## Sample question 2 - Foundation

A student investigated the number of ribwort plants in a field.

The student used a quadrat and a 100 metre tape measure.

This is the method used.

• Place the quadrat in an area where there are lots of ribwort plants in the field.
• Count the number of ribwort plants inside a quadrat.
• Repeat steps 1 and 2 four more times.

Another group of students did an investigation in the field.

The diagram shows how the students placed their quadrats in this investigation.

Question

a) What is the name given to the line shown in the diagram? [1 mark]

b) The graph below shows the students' results. Describe the relationship shown in the results graph. [2 mark]

a) Transect [1].

b) As distance from the path increases, the number of plants increases [1].

Steep rise from 0.5 to 3.0 between 2 and 4 mm from the path or numbers level off to about 4 plants from 10 m from the path [1].

## Sample question 3 - Higher

Question

Some students wanted to estimate the number of plantain plants in a grassy field.

The field measured 100 metres × 50 metres.

The students:

• chose areas where plantains were growing
• placed 10 quadrats in these areas
• counted the number of plantains in each of the 10 quadrats

Each quadrat measured 25 cm × 25 cm

The students' method would not give a valid estimate of the number of plantain plants in the field.

Describe three improvements you could make to the students' method.

For each improvement, give the reason why your method would produce more valid results than the students' method. [3 marks]

• Improvement: place quadrats randomly
• Reason: avoid bias / more representative / more reliable
[1]
• Improvement: more quadrats
• Reason: overcome random variation / more typical / more representative / more reliable / repeatable
[1]
• Improvement: larger quadrats or repeat when plants are bigger
• Reason: less likely to miss plants
[1]

## Sample question 4 - Higher

Question

Students investigated a food chain in a garden.

lettuce → snail → thrush (bird)

The students:

• estimated the number of lettuce plants in the garden
• estimated the number of snails feeding on the lettuces
• counted two thrushes in the garden in 5 hours

Below are the students' results and calculations.

OrganismPopulation sizeMean mass of each organism in gBiomass of population in gBiomass from previous organism that is lost in gPercentage of biomass lost
Lettuce50120.06,000
Snail2002.55005,50091
Thrush285.017033066

Scientists estimate that about 90% of the biomass in food is lost at each step in a food chain.

Suggest one reason why the student’s value for the percentage of biomass lost between the snails and the thrushes is only 66%. [1 mark]

Any one from the following:

• thrushes eat other things [1]
• thrush numbers likely to vary [1]
• thrushes were not present all the time [1]
• thrushes feed on a much bigger area [1]