Soil Class 7 Extra Questions and Answers Science Chapter 9

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In this page, we are providing Soil Class 7 Extra Questions and Answers Science Chapter 9 pdf download. NCERT Extra Questions for Class 7 Science Chapter 9 Soil with Answers will help to score more marks in your CBSE Board Exams.

Class 7 Science Chapter 9 Extra Questions and Answers Soil

Extra Questions for Class 7 Science Chapter 9 Soil with Answers Solutions

Soil Class 7 Extra Questions Very Short Answer Type

Question 1.
Name the best soil for growing plants.
Answer:
Loamy soil

Question 2.
What is soil?
Ans.
The mixture of rock particles and humus is called the soil.

Question 3.
What is humus?
Answer:
The rotting dead matter in the soil is called humus.

Question 4.
What is silt?
Answer:
Silt is a granular material having size between sand and clay.

Question 5.
What is the soft, porous layer of the soil called?
Answer:
It is called top soil or the A-horizon.

Question 6.
Which soil has the largest water holding capacity?
Answer:
Clayey soil has the largest water holding capacity.

Question 7.
List some uses of clayey soil.
Answer:
Clayey soil is used to make pots, toys and statues.

Question 8.
What processes does formation of soil involve?
Answer:
Formation of soil involves two processes:

  • Breaking of rocks
  • Mixing of soil with organic matter.

Question 9.
What is horizon?
Answer:
The soil profile shows three district layers. These layers are called horizons.

Question 10.
What is soil moisture?
Answer:
Soil absorbs water and also hold water in it, which is known as soil moisture.

Question 11.
What do you mean by percolation?
Answer:
Percolation means to pass through a porous substance.

Question 12.
What is loamy soil?
Answer:
The soil with a mixture of silt, sand and clay in equal amount is called loamy soil.

Question 13.
What is soil profile?
Answer:
A vertical section through different layers of the soil is called the soil profile.

Question 14.
What is clayey soil?
Answer:
The soil with large amount of fine particles in it is called clayey soil.

Question 15.
What is bedrock?
Answer:
Bedrock is below the C’horizon. It is the unweathered rock which decides the kind of soil. Question

Question 16.
Which soil contains greater proportion of big particles?
Answer:
Sandy soil

Question 17.
What is soil?
Answer:
The uppermost layer of the earth’s crust in which plants grow is called soil.

Question 18.
What is soil erosion?
Answer:
The removal of top soil by the action of water and wind is called soil erosion.

Soil Class 7 Extra Questions Short Answer Type

Question 1.
Write four important properties of soil.
Answer:
Following are the four important properties of soil:

  1. It absorbs water.
  2. It contains air.
  3. It allows water to percolate.
  4. It supports all life on earth.

Question 2.
What do you mean by deforestation?
Answer:
The process of cutting of trees on large scale which harms the environment is known as deforestation.

Question 3.
How can soil erosion be prevented?
Answer:
Following are the steps by which we can prevent soil erosion:

  1. By step-farming.
  2. By preventing deforestation.
  3. By constructing dams.
  4. By planting more and more trees.

Question 4.
List the six types of soil found in India.
Answer:
Following are the six types of soil found in India:

  1. Red soil
  2. Black soil
  3. Alluvial soil
  4. Desert soil
  5. Mountain soil
  6. Laterite soil

Question 5.
How is soil formed?
Answer:
Soil is formed from weathering of rocks which is also known as parent material. Weathering of rocks can be caused by two methods: physical and chemical.

Question 6.
What is meant by reforestation?
Answer:
Large scale plantation or renewing forest cover in place of destroyed or existing forests is called reforestation.

Question 7.
What is humus?
Answer:
Nutrient materials formed by the breakdown of plant and animal remains by the action of bacteria and other microorganism is called humus. Humus increases the water holding capacity of the soil and provide nutrients to the growing plants.

Question 8.
What are the uses of soil?
Answer:

  1. Soil supports growth of all living organisms.
  2. It act as habitat for many organisms.
  3. Soil are sources of minerals and salts.
  4. Soil is used for making bricks, houses, toys, pots, etc.

Soil Class 7 Extra Questions Long Answer Type

Question 1.
Explain physical properties of soil.
Answer:

  1. Soil colour: Soil can be black, red, brown or grey in colour.
  2. Water-holding capacity: The ability of a particular soil to hold water is called its water holding capacity.
  3. Soil texture: Roughness, grittiness and smoothness are the properties which gives soil texture. It depends on the amount of sand, silt and clay in a particular soil.
  4. Acidity or alkalinity: Based on minerals and salts found in a particular area, the soil may be acidic or alkaline. Determining this property of soil is very important to decide which kind of vegetation can be grown in that area.
  5. Soil structure: Soil structure refers to the way in which soil particles aggregates together. Soil structure modifies the effect of texture in regard of nutrient availability, moisture and air content.

Question 2.
What is soil? Write few lines about different types of soil.
Answer:
Soil is a substance which makes up the surface of the earth. It holds inorganic and organic substances and dead parts of plants and animals.
The soil is classified on the proportion of particles of various sizes:

  1. Sandy soil: Soil contains lot of sand and is light in weight. This type of soil has a lot of air spaces and has high percolating rate. It has least water holding capacity and is poor in nutrients.
  2. Clayey soil: The soil with large amount of clay particles in it is called clayey soil. It has the highest water holding capacity. It is heavy and does not let air pass through it easily.
  3. Loamy soil: The soil with a balanced mixture of humus, sand and clay is called loamy soil. The best topsoil for growing plants is loamy soil because of its good water holding capacity. It is fit for cultivation.

Question 3.
What is percolation rate? Define with its formula.
Answer:
Percolation is the process of passage of water from the surface into the soil. The rate of percolation is different for different types of soils. The rate of percolation depends on soil structure and texture. A soil with more percolation rate will hold water for shorter time and vice versa. Sandy soil has highest percolation rate whereas clayey soil has least percolation rate.

The rate of percolation can be calculated by using the following formula:
Amount of water (mL/min.) = \(=\frac{\text { Amount of water }(\mathrm{mL})}{\text { Percolation time }(\mathrm{min} .)}\)
For example, if for a given sample of soil, it took 20 minutes for 200 mL to percolate then,
Percolation rate = \(\frac {200 mL}{20min.}\) = 10 mL/min

Question 4.
Explain soil profile with a suitable diagram.
Answer:
Soil profile is a vertical section through different layers of soil. Each layer differs in feel (texture), colour, depth and chemical composition.
These layers are referred to as horizon.

  1. Horizon-A: It is the uppermost layer and is dark in colour due to presence of humus and minerals. This layers provide shelter to many organisms. The roots of small plants are embedded entirely in the top soil.
  2. Horizon-B: This layer contains lesser amount of humus but more minerals. This layer is generally harder and more compact.
  3. Horizon-C: This layer is made up of small lumps of rocks with cracks and crevices. Below this layer is the bedrock.

Soil Class 7 Extra Questions and Answers Science Chapter 9 1

Question 5.
What are the various factors that influence soil formation?
Answer:
Soil is formed from the weathering of parent rocks. Formation of soil is a continuous process. This process is affected by various factors like climate, time, parent material, relief, etc.

  1. Time: Soil formation need time. A newly exposed surface will have very little soil if any, while old surfaces will have deeper soils.
  2. Climate: Temperature and humidity of a place has key role in the formation of soil. Warmer climate with more rainfall will speed up the formation of soil.
  3. Relief: This refers to landscape position and the slopes it has. In steep slope water will run down faster eroding its surface. In gentle slope less erosion of top soil will occur and in flat land erosion will be least, and soil will be found.
  4. Parent material: The soil formed will carry the characteristics of its parent material such as colour, texture, structure, mineral composition and so on. The nature of parent material also decide how long it will take to form soil.

Soil Class 7 Extra Questions and Answers Science Chapter 9 2

Soil Class 7 Extra Questions HOTS

Question 1.
Is it a good practice to remove grass and small plants from open or unused filed? Why?
Answer:
No, because roots of grass and small plants bind the soil particles and hold them in place. Thus, they help to prevent soil erosion.

Question 2.
In Rajasthan, during rainy season, several rivulents of rainwater is a common scene but stream of water is very rare. Explain.
Answer:
Deserts have vast stretches of sand. Sandy soil has high rate of percolation. So it percolates rainwater immediately downwards in the spaces between sand.

Question 3.
Why continuously water-logged soils are harmful for standing crops?
Answer:
In water-logged soils, water occupies the spaces between soil particles and thus making roots deprive of available air. This affects of growth of the crops and consequently the crops die.

Question 4.
Why gardeners gently dig up the soil around the roots of garden plants frequently?
Answer:
Gardeners gently dig up the soil around the roots of garden plants to

  1. remove weeds
  2. aerate the soil
  3. facilitate percolation
  4. loose the soil for easy root growth

Question 5.
Why water table is very deep in cities in comparison to villages?
Answer:
In cities vast areas of soil are concreted and their is very less space for percolation of water. In cities, consumption of water is more as it is highly populated. In contrast to cities condition in villages it is quite opposite. It has more areas for percolation, more vegetation, good water cycle, etc. Thus, water table is very deep in cities in comparison to villages.

Soil Class 7 Extra Questions Value-Based (VBQs)

Question 1.
Being a part of project assignment Prabha and Priyanka, both planted some ornamental plants in their school garden individually. Prabha always kept the surrounding ground of the plant clear and watered it regularly. Priyanka did not removed the litter around the plants, watered them and sometime gently dig up the soil around the roots.
(a) Who do you think will be able to grow healthier plant?
(b) What is the role of humus?
(c) Is providing excessive fertilisers to the plant good?
(d) What values of Priyanka and Prabha are shown here?

Answer:
(a) Priyanka will be able to grow healthier plant because she didn’t removed the litter from the soil which will aid in providing nourishment to the plant on degradation. Digging gently around the plant will help in better root penetration, recycling of nutrients, providing air and increasing water holding capacity of soil.
(b) The dead and decomposed organic matter in the soil is called humus. It plays a very important role in maintaining fertility of the soil, increasing water holding capacity, changing soil structure for sustaining plant growth, etc.
(c) No. Excessive fertilisers increase soil alkalinity or acidity and thus declines plant growth.
(d) Both, Priyanka and Prabha are sincere with the work assigned to them. Prabha, is inexperienced in growing plants. Priyanka, on other hand, is skilled and understand the needs of plants.

Question 2.
When Tanya’s teacher asked her about the components of soil, she remained unanswered. So her teacher gave her home task to dig some soil form the garden and to observe it carefully under the hand lens. Tanya’s teacher also asked her to write observations of the activities like, dissolving soil in water and weighing salt before and after drying it. Tanya in her observations found that soil contains small organisms, dead and decaying matter, air, gravel, plastic articles, moisture, etc.
(a) Are all components listed by Tanya correct? Why?
(b) How one of the soil component listed by Tanya is not good for soil health?
(c) Name same soil pollutants.
(d) What value of Tanya is shown here?

Answer:
(a) No, because plastic articles are not naturally found in the soil but are added to it due to human activities.
(b) Plastic articles are not easily degradable by soil microbes. They can also kill the beneficial organisms living in the soil and can also clog the soil porosity.
(c) Plastic, polythene, chemicals, pesticides, etc.
(d) Tanya is obedient, hardworking and a good observant. She noted down all the things as instructed by her teacher.