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
NCERT Solutions for Class 7 Science Chapter 9 Soil
Answer :
(iii) Minerals, organic matter, air and water
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
NCERT Solutions for Class 7 Science Chapter 9 Soil
Answer :
Column I. Column II
(i) A home for living organisms
(ii) Upper layer of the soil
(iii) Sandy soil
(iv) Middle layer of the soil
amount of humus
(v) Clayey soil
packed tight
NCERT Solutions for Class 7 Science Chapter 9 Soil
Answer :
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. 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 soil.
NCERT Solutions for Class 7 Science Chapter 9 Soil
Answer :
Due to the very small size of the particles of clayey soil, particles are packed tightly and therefore can retain water. Clayey soil is also rich in organic matter. 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 kind of crops.
NCERT Solutions for Class 7 Science Chapter 9 Soil
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.
NCERT Solutions for Class 7 Science Chapter 9 Soil
Answer :
Amount of water = 200 ml
Percolation time = 40 minutes
=
NCERT Solutions for Class 7 Science Chapter 9 Soil
Answer :
Prevention of soil pollution:
The persistent build-up of toxic compounds in the soil is defined as soil pollution. To prevent soil pollution, its causes must be controlled.
(i) Plastics and polythene bags destroy the fertility of the soil. Hence, they should be disposed properly and if possible, their use should be avoided.
(ii) Some waste products from industries and homes pollute the soil. These pollutants should be treated chemically to make them harmless before they are disposed of.
(iii) Other pollutants of soil include pesticides and insecticides. Therefore, the excessive use of these substances should be avoided.
Prevention of soil erosion:
Removal of the upper fertile layer of the soil (top soil) by strong wind and flowing water is known as soil erosion.
(I) Planting more and more trees will result in the reduction of soil erosion.
(ii) By stopping deforestation and avoiding overgrazing of animals.
Q.10 Solve the following crossword puzzle with the clues given:
NCERT Solutions for Class 7 Science Chapter 9 Soil
Answer :