NCERT Class 7 Science Chapter 9 Soil

NCERT Class 7 Science Chapter 9 Soil Solutions to each chapter is provided in the list so that you can easily browse through different chapters NCERT Class 7 Science Chapter 9 Soil and select need one. NCERT Class 7 Science Chapter 9 Soil Question Answers Download PDF. NCERT Class 7 Science Solutions.

NCERT Class 7 Science Chapter 9 Soil

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Also, you can read the NCERT book online in these sections Solutions by Expert Teachers as per Central Board of Secondary Education (CBSE) Book guidelines. CBSE Class 7 Science Solutions are part of All Subject Solutions. Here we have given NCERT Class 7 Science Chapter 9 Soil and Textbook for All Chapters, You can practice these here.

Soil

Chapter: 9

NCERT TEXT BOOK EXERCISES

Tick the most suitable answer in questions 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.

Ans: (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

Ans: (iii) loamy soil.

Q.3. Match the items in column I with those in column II:

Ans:

Q.4. Explain how soil is formed. 

Ans: (i) The big and heavy rocks are broken into smaller pieces come on the surface of the earth.

(ii) Soil is formed by breaking down of rocks by the action of wind, water and climate. This process is called weathering.

(iii) The smaller particles of the rocks obtained due to weathering get further decomposed on long expose to air moisture.

(iv) Finally the decomposed part 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.

Q. 5. How is clayey soil useful for crops? 

Ans: Clayey soil have good water retaining capacity. It is rich in humus and is very fertile. This is the reason why this soil is useful for growing crops like wheat and rice.

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

Ans:

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

Ans:

Fig. 9.12. Soil profile.

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. 

Ans: Formula: Percolation rate

Q. 9. Explain how soil pollution and erosion could be prevented:

Ans: Prevention of soil pollution:

(i) Dispose off sewage properly.

(ii) Recycle waste.

(iii) Use organic manure or vermicompost. 

(iv) Treat industrial effluents before discharge.

Prevention of soil erosion:

1. Grow more trees on a large scale (afforestation). 

2. Flood control.

3. Allow restricted animal grazing.

4. Follow terrace farming. 

5. Construct bunds.

Q. 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.

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.

Ans:

ADDITIONAL IMPORTANT QUESTIONS

Very Short Answer Questions 

Q. 1. When some dry soil is added to water in a beaker and stirred with a glass rod, bubbles are seen coming out of the soil. What do these bubbles consist of?

Ans: Air.

Q. 2. Which component of soil makes the air above the soil in a farmland shimmer on a hot summer day?

Ans: Water.

Q. 3. Which type of soil: 

(a) is the best for making pots, bricks, toys and statues?

Ans: Clayey soil.

(b) can hold very little water? 

Ans: Sandy soil.

Q. 4. Name the rock particles present in a soil which are bigger than clay particles but smaller than sand particles. 

Ans: Silt.

Q. 5. Arrange the following rock particles which occur in soil in the increasing order of their sizes (keeping the smallest one first):

Sand, Clay, Gravel, Silt

Ans: Clay < Silt < Sand < Gravel.

Q. 6. Name the natural process which breaks down huge rocks slowly to form tiny particles fit to make soil.

Ans: Weathering.

Q. 7. With which substance should the tiny rock particles mix to form fertile soil?

Ans: Humus.

Q. 8. Out of sand, loamy and clayey soils:

(a) Which one has the maximum water-holding capacity? 

Ans: Clayey soil.

(b) Which one has the minimum water holding capacity?

Ans: Sandy soil.

Q. 9. What lies beneath C-horizon?

Ans: Bed rock.

Q. 10. What is humus?

Ans: It is dark coloured partially decayed organic matter rich in nutrients. It makes soil porous thereby increasing its air and water holding capacity.

Short Answer Type Questions 

Q. 1. Why is the sandy soil called well aerated soil?

Ans: The sand particles in sandy soil are quite large. Since large particles cannot pack themselves closely, there are large number of gaps (empty spaces) between them. Such gaps are filled with air. So, sandy soil is called well- aerated soil.

Q. 2. Explain which horizon of soil is most suitable to grow plants and why?

Ans: The A-horizon, which is the upper most layer of soil profile is most suitable to grow plants because:

(i) It has more humus which increases the fertility of soil.

(ii) It is porous, soft and retains more water. 

Q. 3. Soil formation is done by both abiotic and biotic factors. List the names of these factors by classifying them as abiotic and biotic.

Ans: (i) Sun, water and wind-Abiotic factors. 

(ii) Lichens, mosses, other plants (herbs, shrubs and trees-Biotic factors).

Q. 4. State the important properties of soil.

Ans: (i) Soil contains air. 

(ii) Soil contains water (or moisture).

(iii) Soil can absorb water.

(iv) Soil allows water to percolate.

Q. 5. Explain why, if we pass through a farmland during a hot summer day, the air above the land appears to be shimmering. 

Ans: The soil in the farmland contains some water. On a hot summer day, this water of soil evaporates forming water vapor. The water vapor coming out of the soil reflects to the sunlight irregularly due to which the air above the soil seems to be shimmering.

Q. 6. What is sandy soil? Give any two properties of sandy soil.

Ans: Soils having more than 60 percent sand along with same clay are called sandy soils.

Properties of sandy soil:

(i) The water holding capacity of sandy soil is very poor. 

(ii) Sandy soil is light, well aerated and rather dry.

Q. 7. What makes soil as a shelter for many living organisms?

Ans: Soil contains organic materials, such as starch, sugar, cellulose, fats and proteins. These give energy to living organisms. Air, water and minerals also give enough energy to living organisms to sustain themselves.

Q. 8. How is loamy soil very useful for the crops?

Ans: Loamy soil contains sufficient amount of humus. So, loamy soil has all the necessary nutrients for the growth of plants. Loamy soil is the most fertile soil. So loamy soil is very useful for the crops.

Short Answer Type Questions

Q. 1. 200 g of a soil is taken and dried completely in bright sun shine. The mass of dried soil is found to be 170 grams. Calculate the percentage of water (or moisture) present in the given sample of the soil.

Q. 2. 100 mL of water was taken in a given measuring cylinder. This water was added dropwise to 50 g of dry soil kept on filter paper in a funnel. When the water just started dripping from the soil in the funnel, the amount of water left in the measuring cylinder was found to be 80 mL. Calculate the percentage of water absorbed by this soil.

Ans. Initial volume of water, V₁ = 100 mL

Find volume of water, V₂ = 80 mL

Mass of soil taken, m = 50 g 

Percentage of water absorbed

Q.3. Name three parameters that decide which type of plants will thrive on that soil. 

Ans: The three parameters that decide the type of plants in a particular soil are: 

(i) The nutrient content of the soil.

(ii) The amount of humus present in the soil.

(iii) The depth of the soil.

Q. 4. How does absorption of water by soil differ from percolation of water through soil?

Ans: Water absorption capacity of a soil is described in terms of the amount of water absorbed by a particular type of soil. High water absorption means higher water retention capacity of the soil. Percolation property of any material is linked to its porosity. Different soils have different porosity. Therefore, water percolates differently through different soils. Percolation rate of water in the soil

Long Type Questions Answer 

Q. 1. What is soil erosion? How can soil erosion be prevented? 

Ans: Soil erosion: The process of carrying away of fertile top soil by wind or by the flowing water is called soil erosion.

Soil erosion can be prevented by the following methods: 

(i) By planting more trees and grass: Roots of trees bind the soil particles together and prevent soil erosion.

(ii) By step farming: In hilly areas, the step farming method prevents soil erosion by reducing the speed of flowing water.

(iii) By constructing dams, check-dams and river embankments: The embankments of rocks and stones along the river banks and check-dams prevent soil erosion.

(iv) By preventing overgrazing: Overgrazing by animals results in the removal of the green cover on the land. Bare soil suffers erosion severely. So by preventing overgrazing, the green cover on the land is protected. As a result, soil is not eroded.

Q. 2. What is the composition of soil? Name the important crops and the types of soils which are suitable for growing these crops. 

Ans: Soil is composed of air, water, minerals and humus:

(i) Clayey soil and loamy soil are both suitable for growing cereals like wheat, and gram. Such soils are good at retaining water. The best soil for growing wheat crop is, however, loamy soil. This is because loamy soil is rich in humus and very fertile.

(ii) Soil rich in clay and organic matter, and having very good capacity to retain water is ideal for growing paddy (rice crop).

(iii) For growing lentil (masoor dal) and other pulses, loamy soil which drains water easily, is required.

(iv) For growing cotton crop ‘sandy-loam soil’ which drains water easily and can hold plenty of air in it, is more suitable.

Q. 3. (a) Soil A has a high percolation rate of water whereas soil B has a low percolation rate of water. Which of the two soils, A or B is most suitable for growing paddy (rice crop)? Why?

Ans: Soil B. Paddy (rice crop) needs a lot of standing water for its growth. 

(b) Why soil organisms are important? 

Ans: Soil organisms are important because of various uses:

(i) Earthworms burrow the soil, shallow it and make it loose and soft.

(ii) Microorganisms cause the decomposition of dead plants and animals, and release the minerals back to the soil. The minerals can again be absorbed by the plant roots. Mineral cycling goes on in this manner.

(iii) Some bacteria are able to fix nitrogen in association with roots of legume plants like pea and gram.

HOTS QUESTIONS

Q.1. Name two measures which prevent the soil erosion. 

Ans: (i) Intensive cropping.

(ii) Terrace farming.

Q. 2. How type of soil is decided?

Ans: The type of soil is decided by the average size of particles found in it and the quality of the soil in decided by the amount of humus and the microscopic organisms found in it.

Q. 3. What role is played by the sun in the formation of soil? 

Ans: (i) It causes expansion of rocks during day.

(ii) At night, these rocks cool down and contract. 

(iii) Since all parts of the rock do not expand and contract at the same rate. This causes formation of crakes in huge rocks and they ultimately crack into very small particles, thus forming soil.

SKILL BASED QUESTIONS

Q. 1. (i) Draw a diagram to show different layers of soil

(ii) Label the various layers. 

(iii) Define the term humus.

Ans: (i), (ii)

Fig. 9.15, Layers of soil.

(iii) The rotting dead matter in the soil is called humus.

Q. 2. Observe the following figure and answer the questions that follow: 

(i) Label the parts of figure marks: (1), (2), (3) and (4) 

Ans: This figure shows the soil profile: (1) A-horizon (2) B-horizon (3) C-horizon (4) Bed rock.

(ii) Which part of the soil is more suitable to grow plants? 

Ans: (ii) A-horizon is more suitable to grow plants. 

(iii) What is bed rock?

Ans: (iii) Below C-horizon is hard and difficult to dig with spade. This layer is called bed rock. 

Fig. 9.16.

FORMATIVE ASSESSMENT

1. Fill in the following blanks with suitable words:

(i) The mixture of rock particles and humus is called _________.

Ans: Soil.

(ii) Each layer of soil is called a ________.

Ans: Horizon.

(ii) The roots of small plants grow entirely in the ________ soil.

Ans: Top.

(iv) The middle layer of soil is called _____ horizon.

Ans: B.

(v) A vertical section through different layers of soil is called soil ________.

Ans: Profile.

(vi) Trees and other plant roots firmly bind the ________ particles. 

Ans: Soil.

(vii) B-horizon of the soil is lighter in color due to the presence of lesser amount of __________.

Ans: Humus.

(viii) Cutting down of trees on large scale is called _______ .

Ans: Deforestation.

2. State whether the following statements are true or false:

(i) The water-holding capacity is highest in loamy soil. 

Ans: False.

(ii) Capacity to hold water is much in sandy soil than clayey soil. 

Ans: False.

(iii) Upper portion of soil always contains air.

Ans: True.

(iv) Erosion of soil is more severe in areas of high vegetation.

Ans: False.

(v) Clayey soil is used in making pots and toys. 

Ans: True.

(vi) Soil erosion is the removal of top soil by wind or flowing water. 

Ans: True.

(vii) The C-horizon is the layer of soil which is rich in humus.

Ans: False.

(viii) Loamy soil has the right water-holding capacity. 

Ans: True.

3. Match the following:

Ans: 

4. Write one word for the following:

(i) The layered structure of the soil. 

Ans: Soil profile.

(ii) The soil that contains mostly clay particles.

Ans: Clayey soil.

(iii) The property of soil that is linked to its porosity. 

Ans: Percolation rate.

(iv) The soil that is most suitable for plants.

Ans: Loamy soil.

(v) Large scale planting of plants and trees in place of destroyed or dead trees and forests. 

Ans: Reforestation.

(vi) The breaking down of rocks into smaller pieces by natural forces such as water, wind, glaciers, roots of plants, etc.

Ans: Weathering.

(vii) Decomposed and decayed remains of plants and animals that enrich soil.

Ans: Humus,.

(viii) Contamination of soil with excessive fertilizers, pesticides, sewage, garbage. 

Ans: Soil pollution.

5. Multiple Choice Questions: 

(i) The darkest layer of soil is:

(a) top soil

(b) bed rock

(c) C-horizon

(d) sub soil

Ans: (a) Top soil.

(ii) In which of the following humus is present in reasonable amount?

(a) A-horizon 

(b) B-horizon 

(c) C-horizon

(d) bed rock

Ans: (a) A-horizon.

(iii) The water holding capacity is highest in:

(a) sandy soil

(b) clayey soil

(c) loamy soil

(d) mixture of sandy and loamy soils.

Ans: (b) Clayey soil.

(iv) Which of the following present in soil has the smallest sized rock particles?

(a) gravel 

(b) silt

(c) clay

(d) sand

Ans: (c) Clay.

(v) Which one of the following cannot be an effect of soil erosion?

(a) desertification

(b) desalinisation

(c) flooding

(d) famine

Ans: (b) Desalinisation.

(vi) Which of the following cannot prevent soil erosion?

(a) reforestation

(b) deforestation 

(c) silviculture

(d) plantation

Ans: (b) Deforestation.

(vii) Which type of soil can lead to the maximum water logging in the fields?

(a) loamy soil 

(b) clayey soil

(c) sandy soil

(d) sandy-loam soil

Ans: (b) Clayey soil.

(viii) One of the following is not a type of soil. This one is:

(a) loamy soil 

(b) silty soil

(c) clayey soil 

(d) sandy soil

Ans: (b) Silty soil.