Monday, 20 June 2016

TEXTBOOK ANSWERS AND SOLUTIONS OF CBSE CLASS VII SCIENCE Chapter 9 Soil



1) Tick the most suitable answer in questions 1 and 2.
1. In addition to the rock particles, the soil contains
(i) Air and water
(ii) Water and plants
(iii) Minerals, organic matter, air and water
(iv) Water, air and plants

ANSWER:- minerals, organic matter, air and water

2) The water holding capacity is the highest in
(i) Sandy soil
(ii) Clayey soil
(iii) Loamy soil
(iv) Mixture of sand and loam

ANSWER: - clayey soil

3) Match the items in Column I with those in Column II:

ANSWER:- 
                      Column I                                    Column II
(i) A home for living organisms                  -(a)large particle
(ii) Upper layer of the soil                           -(b) All kinds of soil
(iii) Sandy soil                                             -(c) Dark in colour
(iv) Middle layer of the soil                        -(d) Small particles and packed tight
(v) Clayey soil                                             -e) Lesser amount of humus

4)Explain how soil is formed.

ANSWER: The soil is formed by the process of weathering in which the rocks break down by the action of wind, water and climate. It is a very slow process .

5)How is clayey soil useful for crops?

ANSWER:- Clayey soil is very useful for crops because:
(i) It has very good water retaining capacity.
(ii) This soil is rich in humus and is very fertile.

6) List the differences between clayey soil and sandy soil.

ANSWER: -

Clayey Soil:-
(i) It has much smaller particles.
(ii) It can hold good amount of water
(iii) It is fertile.
(iv) Air content is low.

Loamy Soil:-
(i) It has much larger particles.
(ii) It cannot hold water.
(iii) It is not fertile.
(iv) Air get trapped between the particles.

7. Sketch the cross section of soil and label the various layers.

ANSWER:-


8)Razia conducted an experiment in the field related to the rate of percolation. She observed that it took 40 min for 200 mL of water to percolate through the soil sample. Calculate the rate of percolation.

ANSWER:- Amount of water taken = 200mL
Time taken by water to percolate = 40 min
Rate of percolation = Amount of water taken/Time taken by water to percolate = 200 mL/40 min = 5 mL/min

9)Explain how soil pollution and soil erosion could be prevented.




ANSWER: - Steps for preventing soil pollution and soil erosion:
(i) Plantation should be encouraged because plant roots firmly bind the soil and help in preventing erosion.
(ii) Methods like crop rotation and mixed farming should be followed.
(iii) Use of organic fertilizers and manure instead of synthetic.
(iv) Pesticides and insecticides should be used in limited quantity and find natural way to prevent it.
(v) Plastic bags should be banned and it doesn't decompose and gives rise to soil pollution.


Written By Badal Paul
The author is a passionate blogger, writer and educationalist. This blog is created to ease troubles of the Cbse students. The author holds multiple blogs and the writer of the Novel KALCHAKRA, OOM AND THE CHOSEN FIVE.