Agriculture Paper 3, WASSCE (PC 2ND), 2018

Question 1

     

  • 1. The diagram below illustrates an experimental set-up in soil analysis. Study it carefully and answer the questions that follow.


    Soil sample being dried with a bunsen burner
    (a) State the aim of the illustrated experiment.  (1 mark)


    (b) Name the part labelled I, II, III and IV.   (4 marks)

     

    (c)  A fresh sample of soil weighed 60 g. A container weighing 35 g was used to dry the soil. If both the soil and the container weighed 80 g after the experiment, determine the:
    (i) weight of the dried soil;  (2 marks)
    (ii) weight of the water lost from the soil;   (2 marks)
    (iii) percentage of water lost from the soil.   (3 marks)

     

    (d) List three forms in which water exists in the soil. (3 marks)

Observation

  •  

    This question was not popular among candidates.
    (a) Many candidates were unable to state the aim of the experiment as well as name the illustrated parts in the experimental set-up.

    (b) Candidates performed poorly in the calculations on soil analysis.

    (c) Most candidates were however able to mention the forms in which water exists in the soil.

     

     

    The expected answers include:

    (a)  Aim of the illustrated experiment

    Determination of moisture content of a soil sample or organic matter content of the soil.
                                                                                      
    (b)  Labelled parts in the illustrated experiment
    I   -  Evaporating dish/ crucible
    II  -  Soil
    III - Tripod stand
    IV - Bunsen burner                                                                                                                
    (c) (i)  Weight of dried soil
    Weight of empty evaporating dish  =  35g
    Weight of dish  +  dried soil  =  80g
    Weight of dried soil only  =  (80 - 35)g                                                    
    =  45g

                                                                     
    (ii) Weight of water lost from the soil
    (60 - 45)g                                                                                           
    =  15g                                                                                             
    OR
    (95 - 80)g                                                                                           
    =  15g                                                                                                                                                           
    (iii) Percentage of water lost from the soil

                                                                                    

     (d)  Forms in which water exists in the soil

    • Hygroscopic water
    • Capillary water
    • Gravitational water