NCERT Solutions for class 7 science Chapter 9

Soil

ncert solutions class 7 science Exercise Question

Tick the most suitable answer in questions 1 and 2.

Question 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.

Question 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

Question 3

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

Answer

Question 4

Explain how soil is formed.

Answer

Soil is formed by the breaking down of rocks by the action of wind, water and climate. This process is called weathering.In this process rocks are converted to small pieces, which eventually turn to soil .

Question 5

How is clayey soil useful for crops?

Answer

Clayey soil is useful for crops for the following reasons

• It contain rich amount of minerals or organic matter
• It has good ability to hold water
• It is also rich in humus and very fertile .So it is suitable for growing crop like wheat and gram.

Question 6

List the differences between clayey soil and sandy soil.

Answer

Question 7

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

Answer

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.

Solution:

Amount of water = 200 ml

Percolation time = 40 minutes

Percolation rate =
=

= 5ml/min

Question 9

Explain how soil pollution and soil erosion could be prevented

Answer

Prevention of soil pollution :

• industrial waste should be treated before disposed in soil .
• By using organic manure insted of chemical fertilisers and pesticides
• we should not disposed plastic in soil it reduce the fertilty of soil

Prevention of Soil erosion

• By using different method of croping like Crop Rotation,Strip Farming
• By afforestation
• By avoiding overgrazing of animals.

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.

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.

Answer

Across:

2. Erosion

5. Polythene

6. Clay

7. Earthworm

Down:

1. Wind

3. Wheat

4. Sandy

5. Profile