Study Materials

NCERT Solutions for Class 7th Science

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Exercise

Tick the most suitable answer in questions 1 and 2.

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

(iii) Minerals, organic matter, air and water.

2. The water holding capacity is the highest in

(i) sandy soil      (ii) clayey soil

(iii) loamy soil     (iv) mixture of sand and loam

(ii) Clayey soil.

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

Column I                          Column II

(i) A home for living organisms    (a) Large particles

(ii) Upper layer of the soil         (b) All kinds of soil

(iii) Sandy soil                    (c) Dark in colour

(iv) Middle layer of the soil        (d) Small particles and packed tight

(v) Clayey soil                    (e) Lesser amount of humus

4. Explain how soil is formed.

Soil is formed by the breaking down of rocks by the action of wind, water and climate. This process is called weathering and further addition of humus formed by the decomposition of organic matter on the earth's surface make it fertile.

5. How is clayey soil useful for crops?

Clayey soil retains water to a great extent. Thus the crops which require more water such a soil as, wheat etc. Grow well in clayey soil.

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

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

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.

Rate of percolation (mL/ min)

= amount of water (ml)

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

Cutting of trees and deforestayion should be effort should be made to increase the green areas.

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.

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