The NCERT solutions class 7 Science chapter 9 Soil is one of the important topics for the students of 7th standard. The solutions for soil are provided here to help students not only clear their doubts easily but also to understand the chapter in an easy and more effective way.
Because the uses of soil are massive and its application is countless, knowing more details about it by solving the questions and answers upon it will help you to answers questions in exams regarding this topic. This chapter consists of various questions such as identifying the processes as physical and chemical change. It also has various true and false questions regarding which kind of process are classified into chemical change. Here, the solutions are also available in PDF format which students can download and access according to their own convenience.
Question 1. In addition to the rock particles, the soil contains
(i) water and plants
(ii) water, air, and plants
(iii) minerals, organic matter, air, and water
(iv) air and water
The soil contains minerals, organic matter, air, and water in addition to rock particles.
Question 2.Which soil has the highest water holding capacity
(i) loamy soil
(ii) clayey soil
(iii) sandy soil
(iv) the mixture of sand and loam
Clayey soil has the highest water holding capacity.
Question 3. Match following:
|Column I||Column II|
|(i) A home for living organisms||(a) Large Particles|
|(ii) The upper layer of the soil||(b) All kinds of soil|
|(iii) Sandy soil||(c) Dark in color|
|(iv) The middle layer of the soil||(d) Small particles and packed tight|
|(v) Clayey Soil||(e) The lesser amount of humus|
|Column I||Column II|
|(i) A home for living organisms||(a) All kinds of soil|
|(ii) The upper layer of the soil||(b) Dark in color|
|(iii) Sandy soil||(c) Large Particles|
|(iv) The middle layer of the soil||(d) The lesser amount of humus|
|(v) Clayey Soil||(e) Small particles and packed tight|
Question 4. Explain the formation of soil.
The soil is formed by weathering. Weathering of a soil refers to the breaking of bigger rocks into smaller particles. Weathering occurs in 3 ways:
Physical (Sun, water, wind, etc.)
Sun: The rocks are heated by the Sun during the day and they expand. During the night, the temperature falls and the rocks start cooling down and thus, start contracting. The expansion and contraction of the rocks do not occur at the same rate which results in crack-formation. These cracks ultimately break the huge rock into smaller pieces.
Water: Due to uneven heating and formation of cracks, the water gets into those cracks. When this water later freezes, the cracks widen. Fast flowing water also carries rock particles while flowing downstream. These rocks hit other big rocks and wear them down into smaller particles. These particles are then taken along by the water and are deposited down its path. In this way, even flowing water wears away hard rocks over a long period of time.
Wind: Rocks are eroded by strong winds and sand is also carried from one place to the other by winds.
Chemical weathering involves several chemical processes like hydration, hydrolysis, oxidation, reduction, etc. In this type, carbonic acid (present in water) and acidic substances (derived from the decomposition process of organic matter present in the soil) breaks the complex compounds.
Mosses, lichens, and other plants living on the rocks produce acids which accelerate the rock weathering process.
Question 5. How is clayey soil useful for crops?
Clayey soil is useful for crops because of the following reasons:
1)Good water holding capacity.
2) Clayey soil is very fertile and rich in humus.
3) It also contains useful organic minerals.
Question 6. Write the differences between clayey and sandy soils.
|Clayey Soil||Sandy Soil|
|Particles are small in size.||Particles are large in size.|
|This soil is rich in humus.||This soil is not rich in humus.|
|It has good water holding capacity||It has a low ability to retain water.|
|In clayey soil, less air is trapped between the particles.||In sandy soil, more air is trapped between the particles|
|Suitable for crops like wheat, paddy, and gram.||Suitable for crops like cotton, peanuts, etc.|
Question 7. Sketch the cross section of soil and label the various layers.
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.
The total amount of water Razia took = 200 mL
Percolation time (as given) = 40 min
Question 9. Explain how soil pollution and soil erosion could be prevented.
To prevent soil pollution, the following ways can be followed:
1. Insecticides and pesticides should be used in a limited amount.
2. Manures should be used instead of chemical fertilizers.
3. Industrial discharge must be treated properly before being released.
To prevent soil erosion, the following ways can be followed:
1. Deforestation should be prevented.
2. Afforestation should be encouraged.
3. Mixed farming and crop rotation should be encouraged.
Question 10. Solve the following crossword puzzle using the clues given:
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.
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. The collective name for layers of soil.
These solutions for chapter 9 are created by subject experts according to the latest CBSE syllabus. Students must practice the solutions regularly to prepare effectively for their examination.