TEST OF PRACTICAL KNOWLEDGE QUESTION
The diagram above illustrates an experimental setup to determine a soil property.
Study them carefully and answer the question that follows;
(a) Suggest a suitable title for the experiment. [1 mark]
(b) Outline the procedure for carrying out the experiment.[ 7 marks]
(c) identify the soil samples in diagrams 1, Il, and ll
(d) State two precautions to be taken when carrying out the experiment.[ 2 marks )
(e)(i) Which of the soil samples is prone to waterlogging?
(ii) Give one reason four your answer in (e)(i)
The diagram shows three identical setups labelled I, II and III. In each, a funnel holds a soil sample, with a plug of cotton wool at the neck of the funnel. Each funnel is mounted over a measuring cylinder which collects the water that passes through the soil. The three funnels hold soils of different texture, and the amount of water collected in each cylinder differs.
(a) Suitable title (1 mark)
An experiment to determine the rate of water percolation (drainage/permeability) through different soil types.
(b) Procedure (7 marks)
- Set up three funnels of equal size and place a plug of cotton wool of equal thickness in the neck of each, to hold back the soil while letting water pass.
- Weigh out equal masses of three different soil samples (sample I, II and III) and place one sample in each funnel.
- Mount each funnel on a clean, dry measuring cylinder so that water dripping through is collected.
- Measure out an equal volume of water (for example \(100\ \text{cm}^3\)) for each setup using a measuring cylinder.
- Pour the water gently onto the surface of each soil sample at the same time and start a stopwatch.
- Allow the water to percolate for the same fixed time (for example 5 minutes), then read the volume of water collected in each cylinder.
- Record the volumes for I, II and III and compare them. The soil that allows the largest volume through in the given time has the highest permeability; the soil that allows the least has the poorest drainage.
(c) Identity of the soil samples
- Diagram I - Clayey soil (fine, closely packed particles).
- Diagram II - Loamy soil (mixture of medium sized particles).
- Diagram III - Sandy soil (coarse, loosely packed particles).
(d) Two precautions (2 marks)
- Use equal masses of soil, equal volumes of water and cotton wool plugs of equal thickness in all three setups, so the comparison is fair.
- Pour the water onto all three samples gently and at the same time, and read the collected volume at exactly the same time interval to avoid errors.
(e)(i) The soil most prone to waterlogging is sample I (clayey soil).
(e)(ii) Clayey soil has very fine particles and small pore spaces (low porosity and low permeability), so water drains through it very slowly and collects on and within the soil, leading to waterlogging. This is confirmed in the experiment by the small volume of water passing into cylinder I compared with the larger volumes collected under the loamy (II) and sandy (III) samples.
The diagram shows three identical setups labelled I, II and III. In each, a funnel holds a soil sample, with a plug of cotton wool at the neck of the funnel. Each funnel is mounted over a measuring cylinder which collects the water that passes through the soil. The three funnels hold soils of different texture, and the amount of water collected in each cylinder differs.
(a) Suitable title (1 mark)
An experiment to determine the rate of water percolation (drainage/permeability) through different soil types.
(b) Procedure (7 marks)
- Set up three funnels of equal size and place a plug of cotton wool of equal thickness in the neck of each, to hold back the soil while letting water pass.
- Weigh out equal masses of three different soil samples (sample I, II and III) and place one sample in each funnel.
- Mount each funnel on a clean, dry measuring cylinder so that water dripping through is collected.
- Measure out an equal volume of water (for example \(100\ \text{cm}^3\)) for each setup using a measuring cylinder.
- Pour the water gently onto the surface of each soil sample at the same time and start a stopwatch.
- Allow the water to percolate for the same fixed time (for example 5 minutes), then read the volume of water collected in each cylinder.
- Record the volumes for I, II and III and compare them. The soil that allows the largest volume through in the given time has the highest permeability; the soil that allows the least has the poorest drainage.
(c) Identity of the soil samples
- Diagram I - Clayey soil (fine, closely packed particles).
- Diagram II - Loamy soil (mixture of medium sized particles).
- Diagram III - Sandy soil (coarse, loosely packed particles).
(d) Two precautions (2 marks)
- Use equal masses of soil, equal volumes of water and cotton wool plugs of equal thickness in all three setups, so the comparison is fair.
- Pour the water onto all three samples gently and at the same time, and read the collected volume at exactly the same time interval to avoid errors.
(e)(i) The soil most prone to waterlogging is sample I (clayey soil).
(e)(ii) Clayey soil has very fine particles and small pore spaces (low porosity and low permeability), so water drains through it very slowly and collects on and within the soil, leading to waterlogging. This is confirmed in the experiment by the small volume of water passing into cylinder I compared with the larger volumes collected under the loamy (II) and sandy (III) samples.
