NCERT Solutions for Class 7 Science Chapter 9 Soil

Tick the most suitable answer in question 1 and 2.
Q.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 :

(iii) Minerals, organic matter, air and water

Q.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 :

(ii) clayey soil

Q.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 :

(ii) clayey soil

Q.3 Match the items in Column I with those in Column II:
Column I
(i) A home for living organisms
(ii) Upper layer of the soil
(iii) Sandy soil
(iv) Middle layer of the soil
(v) Clayey soil
Column II
(a) Large particles
(b) All kinds of soil
(c) Dark in colour
(d) Small particles and packed tight
(e) Lesser amount of humus

Answer :

Column I $?$ Column II

(i) A home for living organisms $?$ (b) All kinds of soil

(ii) Upper layer of the soil $?$ (c) Dark in colour

(iii) Sandy soil $?$ (a) Large particles

(iv) Middle layer of the soil$?$ (e) Lesser amount of humus

(v) Clayey soil$?$ (d) Small particles and packed tight

Q.4 Explain how soil is formed.

Answer :

(1) The outer layer or the uppermost layer of the earth is formed of soil. The soil is a mixture that contains minerals, organic matter, and living organisms all of which interact slowly yet constantly.

(2) Soil is formed through the process of weathering. Weathering is a process of physical breakdown and chemical decomposition of rocks and minerals near or at the surface of the earth. .

(3) Rock is broken down into small particles. These small particles mix with humus (organic matter) and form soil.

(4) This physical and chemical decomposition is primarily done by wind, water, and climate. As a result of these processes, large rock pieces are converted into smaller pieces and eventually to the soil.

Q.5 How is clayey soil useful for crops?

Answer :

Clayey soil is useful for crops for the following reasons:

(1) Due to the very small size of the particles of clayey soil, particles are packed tightly and therefore can retain water.

(2) Clayey soil is also rich in organic matter. Clayey soil is rich in humus and is very fertile. For growing crops such as wheat, gram, and paddy, the soil that is good at retaining water and rich in organic matter is suitable.

Therefore, clayey soils having these characteristics are useful for such kinds of crops.

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

Answer :

Clayey soil :

(i) Particles are tightly packed.
(ii) It has much smaller particles.
(iii) Very little air is trapped between the particles
(iv) Rich in humus and organic substance.
(v) Good for growing various crops.

Sandy soil :

(I) Particles are loosely packed.
(ii) It has larger particles than clayey soil.
(iii) More air is trapped between the particles.
(iv) Not rich in humus and organic nutrients.
(v) Not suitable for growing crops.

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

Answer :

Q.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 = 200 ml

Percolation time = 40 minutes

$?$ Percolation rate =$\frac{amountofwater}{percolationtime}$

= $\frac{200ml}{40min}$ = 5 ml/min

Therefore, rate of percolation is 5 ml/min