Class 7 Science NCERT Solutions for Chapter – 9 Soil

Soil

Question 1.
In addition to the rock particles, the soil contains

  1. air and water
  2. water and plants
  3. minerals, organic matter, air and water
  4. water, air and plants

Solution:
3. minerals, organic matter, air and water

Question 2.
The water holding capacity is highest in

  1. sandy soil
  2. clayey soil
  3. loamy soil
  4. mixture of sand and loam

Solution:
2. clayey soil

Question 3.
Match the items in Column I with those in Column II :

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

Solution:
(i)-(b)
(ii)-(c)
(iii)-(a)
(iv)-(e)
(v)-(d).

Question 4.
Explain how soil is formed.

Solution:

  1.  The big and heavy rocks are broken into smaller pieces come on the surface of the earth.
  2. Soil is formed by breaking down of rocks by the action of wind, water and climate. This process is called weathering.
  3.  The smaller particles of the rocks obtained due to weathering get further decomposed on long exposure to air and moisture.
  4.  Finally the decomposed parts of dead plants and animals get mixed up with soil formed by above processes. This gives the soil enough energy in the form of organic matter.

Question 5.
How is clayey soil useful for crops?

Solution:
Clayey soil retains water to a great extent. Thus the crops which require more water grow well in clayey soil.

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

Solution:

S. No.Sandy soilClayey soil
(i)High percolation rateLow percolation rate
(ii)Low water retention capacityHigh water retention capacity

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

Solution:
NCERT Solutions for Class 7 Science Chapter 9 Soil image 1

Question 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.
Given, amount of water = 200 mL
Time taken = 40 min
Rate of percolation (mL/min) = \frac { Amount of water(mL) }{ Amount of water(mL) }
\frac { 200 ml}{ 40 Min }
= 5 mL / min .

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

Solution:
Prevention of soil pollution :

  1. There should be a ban on polythene bags and plastics.
  2. Waste products and chemicals should be treated before they are released into the soil.
  3. The use of pesticides should be minimised

Prevention of soil erosion :

  1. By growing trees.
  2. Avoid deforestation.
  3. Maintaining porous structure of soil.
  4. Control and reclamation of ravines and shifting of cultivation.

Question 10.
Solve the following crossword puzzle with the clues given :
Across

2. Plantation prevents it.
5. Use should be banned to avoid soil pollution.
6. Type of soil used for making pottery.
7. Living organism in the soil.
NCERT Solutions for Class 7 Science Chapter 9 Soil image 2

Down
1. In desert soil erosion occurs through.
3. Clay and loam are suitable for cereals like.
4. This type of soil can hold very little water.
5. Collective name for layers of soil.

Solution:
NCERT Solutions for Class 7 Science Chapter 9 Soil image 3

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