Living Science 2019 Solutions for Class 7 Science Chapter 10 Soil are provided here with simple step-by-step explanations. These solutions for Soil are extremely popular among Class 7 students for Science Soil Solutions come handy for quickly completing your homework and preparing for exams. All questions and answers from the Living Science 2019 Book of Class 7 Science Chapter 10 are provided here for you for free. You will also love the ad-free experience on Meritnation’s Living Science 2019 Solutions. All Living Science 2019 Solutions for class Class 7 Science are prepared by experts and are 100% accurate.

Page No 109:

Question 1:

Soil is made up of two main components–one that comes from living things and the other from non-living things. What are these components?

Answer:

The two components of soil are as follows:

1. Humus: Humus is the dark, brown coloured component of the soil and is produced by dead remains of living things.

2. Mineral particles: Mineral particles include minerals such as potassium, calcium and magnesium. These are derived from rocks (non-living things).

Page No 109:

Question 2:

Water expands when it freezes. What role does this play in soil formation?

Answer:

The rain water that enters into the cervices of large rocks, freezes in winters and expands. The expansion of water creates a pressure and leads to the breakdown of large rocks into small fragments, which form soil. 

Page No 109:

Question 3:

What kind of soil will hold more water–one made up of small particles or one with bigger particles?

Answer:

Soil made up of small particles will hold more water as compared to soil made up of bigger particles. This is because small particles pack closely which increases water retention capacity of soil. 

Page No 109:

Question 4:

Farmers generally like the soil to be a mixture of sand, silt, clay and humus. Why? What is such soil called?

Answer:

The soil that is a mixture of slit, sand, clay and humus is preferred by the farmers because it is good for the growth of plants. This type of soil is called loamy soil. Loamy soil contains optimum water retention capacity as well as air trapping ability, which makes it perfect to support plant growth. 

Page No 109:

Question 5:

Soil is formed by weathering of rocks. What does 'weathering' mean?

Answer:

Weathering is a process in which large rocks are broken down into smaller fragments by the action of natural forces such as winds, water and glaciers. The smaller fragments formed by this process form soil. 



Page No 111:

Question 1:

Rainwater percolates through the soil. Where does this water collect? What is the level of this water known as?

Answer:

Percolated rain water collects over the bed rock which lies just beneath the parent rock. The level of water that percolates through the soil is called water table.  

Page No 111:

Question 2:

Soil that has more sand in it absorbs less water than soil that has more clay in it. Which of these allows more water to percolate down?

Answer:

Soil that has more sand has the ability to allow more water to percolate down. This is because the sandy soil is loose and water can easily pass through loose soil. 

Page No 111:

Question 3:

Different crops require different types of soil to grow best. What kinds of soils are best for the following?
a. wheat
b. pulses
c. cotton

Answer:

a. Wheat can be best grown in loamy as well as clayey soils.

b. In order to grow pulses, loamy soils are considered best. 

c. Cotton requires sandy-loam type of soil for its best growth. 

Page No 111:

Question 4:

Name three things for which we depend on the soil.

Answer:

We depend on the soil for the following things:

1. Food, shelter and clothing

2. Minerals

3. Water



Page No 112:

Question 1:

Humus and the smallest particles of rock form the

(a) A-horizon
(b) B-horizon
(c) C-horizon
(d) bedrock

Answer:

(a) A-horizon
Humus and the smallest particles of rock form the upper layer of soil called topsoil or A-horizon.

Page No 112:

Question 2:

Which of these has the smallest size of particles?

(a) sand
(b) silt
(c) clay
(d) gravel

Answer:

(c) clay
Clay has the smallest size of particles, less than 0.002 mm in diameter. Single clay particle cannot be seen with a naked eye.

Page No 112:

Question 3:

Which type of soil is best for growing cotton?

(a) sandy
(b) clayey
(c) loamy
(d) sandy-loam

Answer:

(d) sandy loam
Sandy loam soil is best for growing cotton. It can hold air, but water can drain through it easily.

Page No 112:

Question 4:

Which of these does not cause weathering?

(a) clouds
(b) wind
(c) flowing water
(d) freezing of rainwater

Answer:

(a) clouds
Weathering is the breaking down of huge pieces of rocks into smaller pieces by the action of natural forces such as water, glaciers, wind and roots of plants.



Page No 113:

Question 5:

Water percolating into the soil collects over

(a) A-horizon
(b) B-horizon
(c) C-horizon
(d) none of these

Answer:

(d) none of these
Water percolating into the soil collects above the bedrock. This natural level of groundwater is called the water table.

Page No 113:

Question 6:

Water logging can be expected in soil which is rich in

(a) sand
(b) clay
(c) silt
(d) humus

Answer:

(b) clay
Clayey soil absorbs and retains a lot of water. In clayey soil, stagnant water collects above the soil whenever it rains. This is known as water logging.

Page No 113:

Question 7:

Paddy grows best in

(a) clayey soil
(b) loam
(c) sandy soil
(d) sandy-loam

Answer:

(a) clayey soil
Paddy grows best in soils rich in clay and organic matter with a capacity to retain water.

Page No 113:

Question 1:

Breaking down of rock into smaller pieces by natural forces is called___________

Answer:

Breaking down of rock into smaller pieces by natural forces is called weathering.

Page No 113:

Question 2:

Which absorbs more water-sandy soil or clay?

Answer:

Clayey soil absorbs more water than sandy soil and allows less water to percolate.

Page No 113:

Question 3:

The layer of soil that contains the largest rock pieces is called________

Answer:

The layer of soil that contains the largest rock pieces is called C-horizon.

Page No 113:

Question 4:

In general, which is the best topsoil for growing plants?

Answer:

The best topsoil for growing plants is loam. Loam is a mixture of sand, silt, clay and humus. It has the right water-holding capacity for plant growth.

Page No 113:

Question 5:

Water logging occurs in sandy soil. True of false?

Answer:

False.
Water logging occurs in clayey soil, which absorbs and retains a lot of water. Sandy soil cannot absorb much water because of the large spaces between the soil particles.

Page No 113:

Question 6:

Is soil a natural resource?

Answer:

Yes, soil is a natural resource because it comes from the earth and is used by us.

Page No 113:

Question 7:

Since clay holds more water, it is very good for plants as they get plenty of water. True of false?

Answer:

False.
Although clay holds more water, water drains through soil very slowly since the particles are very small and tightly packed. This type of soil is not able to trap enough air for the roots of the plants.

Page No 113:

Question 8:

Humus is formed by the action of insects on soil. True of false?

Answer:

False.
A variety of dead and decaying organisms contribute to the formation of humus.

Page No 113:

Question 9:

Soil without humus cannot be fertile. True of false?

Answer:

True.
Humus makes the soil fertile by providing organic nutrients.

Page No 113:

Question 10:

Humus if formed by the action of decomposers. True of false?

Answer:

True.
Humus is formed by the action of decomposers such as bacteria and fungi.

Page No 113:

Question 1:

What does soil consist of?

Answer:

Soil consists of two components:
(a) Small mineral particles which come from larger rocks. These minerals include salts of iron, calcium, potassium, magnesium, phosphorus, etc.
(b) Humus is dark brown in colour and consists of decaying remains of plants and animals.

Page No 113:

Question 2:

What is weathering?

Answer:

Weathering is a process by which huge pieces of rocks break down into smaller pieces and gradually change into soil. It takes place by the action of natural forces such as water, wind, roots of plants and variations in day and night temperatures.

Page No 113:

Question 3:

Which soil will allow more water to percolate-sandy soil or clayey soil? Why?

Answer:

Sandy soil will allow more water to percolate because it has a lot of sand and water drains quickly through large spaces between the sand particles.

Page No 113:

Question 4:

Which soil will absorb more water-sandy soil or clayey soil? Why?

Answer:

Clayey soil will absorb more water because the soil particles are very small and the water drains very slowly.

Page No 113:

Question 5:

What is humus?

Answer:

Humus is a component of soil which is dark brown in colour and consists of decaying remains of plants and animals. When small plants such as mosses, lichens and ferns die, they mix with the soil and form humus. Humus makes the soil fertile by providing organic nutrients.

Page No 113:

Question 6:

How does large variation between day and night temperatures cause weathering?

Answer:

Due to large variation in day and night temperatures, the rocks expand during the day and contract during the night. This constant expansion and contraction weakens the rocks and they crack and crumble causing weathering.

Page No 113:

Question 7:

What do you mean by 'water table'?

Answer:

The natural level of groundwater is called the water table. Rainwater percolates through the soil and collects above the bedrock to form the water table.

Page No 113:

Question 1:

Explain how water is responsible for the formation of soil.

Answer:

The role of water in the formation of soil is extremely important in the following ways:
(a) Rainwater which enters rock crevices freezes in winter. As a result, it expands. This expansion puts pressure on rocks and breaks the rocks into smaller pieces.
(b) The small pieces of rocks roll down by the force of flowing water. They collide against the ground and against each other. Hence, they break down further and get converted into very fine particles.

Page No 113:

Question 2:

Trees help in soil formation as well as in its protection. Explain.

Answer:

Roots of trees growing through rocks exert great pressure on the rocks. This pressure causes cracks in the rocks, leading to the formation of soil. The roots of trees bind to the soil and prevent soil erosion and provide protection to the soil.

Page No 113:

Question 3:

Name the different layers of soil. What does each layer consist of?

Answer:

The different layers of soil are as follows:
(i) Topsoil (A-horizon):
It consists of humus and the smallest particles of rock.
(ii) Subsoil (B-horizon):
It consists of small pieces of rocks and some nutrients such as soluble minerals and iron oxides.
(iii) Parent rock (C-horizon):
It consists of small pieces of rocks with cracks and crevices.

Page No 113:

Question 4:

Distinguish between clay, silt and sand.

Answer:

Clay Silt Sand
Particle size is smallest. It is less than 0.002 mm in diameter. Particle size is larger than clay. It is between 0.002 mm and 0.2 mm in diameter. Particle size is largest. It is more than 0.2 mm in diameter.
It can hold a large amount of water. It can hold a small amount of water. Water-holding capacity is most poor.

Page No 113:

Question 5:

What is loam? Why is it considered to be the best topsoil for growing plants?

Answer:

Loam is a mixture of sand, silt, clay and humus.
It is considered to be the best topsoil for growing plants because it has the right water-holding capacity for plant growth. It also has adequate spaces between the soil particles to trap air required by the roots of plants.

Page No 113:

Question 6:

Why is soil regarded as our most important natural resource?

Answer:

Soil is considered as our most important natural resource due to the following reasons:
(a) It provides us food, clothing and shelter: By supporting growth of plants, the soil provides us with food and clothing. Plants also provide us with wood, which is used for constructing house.
(b) It provides us minerals: Minerals are dug out from the earth to extract metals such as iron, gold, silver, etc.
(c) It provides us water: Water that seeps into the soil is stored underground as subsoil water. This water is used for drinking and other purposes.

Page No 113:

Question 7:

Why is the earthworm referred to as 'farmer's friend'?

Answer:

Earthworms improve the soil texture. They make the soil loose by burrowing into the soil, thus allowing air to enter into it and water to drain from it. They also form channels in the soil for roots to spread through. Hence, earthworms are referred to as 'farmer's friend'.

Page No 113:

Question 1:

What effect does construction of buildings and roads have on water percolation through the soil? Hence what effect would this have on the water table?

Answer:

The rate of water percolation through the soil decreases as a result of construction of buildings and roads because water cannot percolate into cement. Due to this, the water table will shrink.



Page No 114:

Question 2:

Soil is constantly formed by weathering of rocks. Why then are we so concerned about soil erosion?

Answer:

Topsoil is the most fertile soil because it consists of humus. Soil erosion removes topsoil, thus decreasing soil fertility. The formation of topsoil by the process of weathering takes a very long time. Hence, we are so concerned about soil erosion.

Page No 114:

Question 3:

Why does topsoil have much more humus than subsoil?

Answer:

Humus is formed by the death and decay of plants and animals. When small plants die, they mix with the soil to form humus. These plants and animals are confined to topsoil. Hence, topsoil have much more humus than subsoil.

Page No 114:

Question 4:

What kind of soil is most suitable for making toys and why?

Answer:

Clayey soil is most suitable for making toys because it does not crumble when rolled into a ball.

Page No 114:

Question 1:

This is a picture of the Grand Canyon in USA. Between the gorge, flows the Colorado River. The gorge has been formed by weathering of rocks over millions of years. What do you think is the cause of the weathering?

Answer:

The Gorge which has been formed due to weathering is a result of change in weather conditions over a period of time.
In winters, the water seeps into the crevices of rocks and as the water freezes it expands and turns into ice. This expansion causes the cracks to become wider and deeper and as a result of this erosion of small stones occurs. 
During rainy seasons, heavy rains causes water to rush down the cracks, further eroding the rocks and stones. As these, rocks crumble and fall away, they cause the widening of the gorge.
This weathering phenomenon has and resulted in the formation of gorge in the Grand Canyon.

Page No 114:

Question 1:

Rahul has a kitchen garden at home. He has built a compost bin in the garden and dumps all the biodegradable garbage from his home into it. He uses the manure formed for his garden. What value does Rahul show?

Answer:

It shows that Rahul is a concerned and aware citizen. He is very much aware of the fact that biodegradable garbage can be used to produce compost. He uses this information in his daily life. He knows how to contribute in solving the growing menace of waste.



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