RBSE Class 7 Science Important Questions Chapter 9 Soil

Rajasthan Board  RBSE Class 7 Science Important Questions Chapter 9 Soil Important Questions and Answers.

RBSE Class 7 Science Chapter 9 Important Questions  Soil

Multiple Choice Questions

Question 1. 
Which of the following type of soil will form a colloidal solution when suspended in water?
(a) Clayey 
(b) Slit
(c) Sandy 
(d) Gravel
Answer:
(a) Clayey 

Question 2. 
The B-horizon is very rich in
(a) fossils 
(b) organic content
(c) mineral content 
(d) fossil fuels
Answer:
(c) mineral content

Question 3. 
While driving along, the roads are cut into the mountains, one is able to see the 
(a) A-horizon 
(b) soil profile
(c) mountain vegetation
(d) alluvial soil
Answer:
(a) A-horizon

Question 4. 
Loamy soil is considered best for :
(a) bricks making 
(b) farming
(c) toy making 
(d) cementing
Answer:
(b) farming

Question 5. 
Size range of sand particles varies between:
(a) 0.05 mm - 2 mm
(b) 2 mm - 20 mm
(c) 0.005 mm - 0.05 mm
(d) Greater than 2 mm
Answer:
(a) 0.05 mm - 2 mm

Question 6. 
Humus makes the soil:
(a) dark 
(b) fertile
(c) porous 
(d) all of these
Answer:
(d) all of these

Fill in the blanks

Question 1. 
Even apparently looking at soil contains some amount of moisture.
Answer:
dry

Question 2.   
soil can be moulded easily, making it apt for manufacturing toys.
Answer:
Clayey

Question 3. 
On a hot summer day, the air above land 
Answer:
spimmers

Question 4. 
Topsoil is generally dark in colour and rich in organic matter.
Answer:
humus

Question 5. 
The roots of plants into the crevices of rocks, break them and help in the process of weathering.
Answer:
penetrate

State Whether True or False

Question 1. 
The various layers of soil comprise its soil profile.
Answer:
True

Question 2. 
Topsoil is the darkest layer of soil due to pollution.
Answer:
False

Question 3. 
The extent to which a soil can be shaped does not indicate its type.
Answer:
False

Question 4. 
The soil type of an area is independent of the wind, rainfall, temperature, light and humidity in that area.
Answer:
False

Question 5. 
The percolation rate of water is not the same in different types of soil. It is the same as the absorption rate.
Answer:
False

Match the following

Column I	Column II
Soil pollution	(a) Vertical section
A-horizon	(b) Deforestation
Soil profile	(c) Chemicals, pesti-cides
Bedrock	(d) Clay
Humus	(e) Sandy loam
Weathering	(f) Topsoil
Best topsoil	(g) Dark organic matter
Erosion	(h) Wind, water
Toys	(i) Hard
Cotton	(j) Loamy soil

Answer:

Column I	Column II
Soil pollution	(c) Chemicals, pesti-cides
A-horizon	(f) Topsoil
Soil profile	(a) Vertical section
Bedrock	(i) Hard
Humus	(g) Dark organic matter
Weathering	(h) Wind, water
Best topsoil	(j) Loamy soil
Erosion	(b) Deforestation
Toys	(d) Clay
Cotton	(e) Sandy loam

Very Short Answer Type Questions

Question 1. 
List 5 uses of soil.
Answer:
Uses of soil:

1. Agriculture; to produce food
2. Pottery
3. Construction
4. Clothing-fibre crops
5. Helps in the decomposition of organic wastes.

Question 2. 
Define soil.
Answer:
Soil is a mixture of rock particles of various sizes and organic matter (humus) that forms the upper layer of Earth in which plants grow.

Question 3. 
Which layer of soil is called topsoil?
Answer:
The soil associated with A-Horizon, on the topmost layer that is visible to us is called top-soil.

Question 4. 
Give an alternative name for sub¬soil?
Answer:
Sub-soil is also called B-Horizon.

Question 5. 
Which is the layer in which most soil creatures reside?
Answer:
Top-soil or A-Horizon.

Question 6. 
What is weathering?
Answer:
The breaking down of rocks by the action of wind, water and climate is called weathering.

Question 7. 
Which soil type is the grainiest? 
Answer:
Sandy soil is the grainiest type of soil. 

Question 8. 
What is silt?
Answer:
Silt is a type of soil found in the deposits of riverbeds, with a particle size somewhere in between that of sand and day.

Question 9. 
Which is the best topsoil for growing plants?
Answer:
The best topsoil for growing plants is loam. It is a mixture of sand, day and silt.

Question 10. 
Which soil type has the highest and lowest percolation rate? 
Answer:
Sand has the highest percolation rate, whereas clay has the lowest.

Question 11. 
What is the formula to determine the percolation rate of soil?
Answer:
Percolation rate (mL/min),amount of water (mL),percolation time (min)

Question 12. 
Which soil type has the highest moisture content? 
Answer:
Clayey soil. 

Question 13. 
Which type of soil can absorb more water?
Answer:
Clayey soil can absorb more water.

Question 14. 
On what factor does the water retention capacity of soil depend? 
Answer:
Partido size.

Question 15. 
Which type of soil is used to make pots, toys and statues?
Answer:
Clayey soil.

Question 16. 
What are the factors which affect the soil profile?
Answer:
Wind, rainfall, temperature, light and humidity affected the soil profile.

Question 17. 
What is erosion?
Answer:
The removal of land surface by water, wind or ice is known as erosion.

Short Answer Type Questions 

Question 1. 
Why is soil called a natural reso¬urce?
Answer:
Soil is called a natural resource because it is produced by natural processes, weathering without the interference of humans and is essential to sustain life on Earth.

Question 2. 
What is soil pollution?
Answer:
The contamination of soil by various means that harms its quality or makes it risky to use either directly or indirectly is called soil pollution. It arises due to the mixing of toxic or non-biodegradable substances in it.

Question 3. 
What is soil composed of?
Answer:
Soil is primarily composed of inorganic components and organic components with some organisms that live on it.

Question 4. 
What is the soil profile?
Answer:
A vertical section through different layers of soil, called horizons, comprises its soil profile. It is revealed upon exposing a vertical section of the soil to the bedrock. 

Question 5. 
What factors determine the colour of soil?
Answer:
Soil colour can be affected by its humus content which makes it appear darker. Another factor could be the type of rock or mineral from which soil is formed, as different minerals have different colours. 

Question 6. 
How is the soil classified on the basis of its particle size?
Answer:
On the basis of particle size soil is classified as either:

1. Sandy soil (0.05 - 2 mm)
2. Clayey soil (<0.02 mm)
3. Silt (0.02 - 0.05 mm)
4. Loamy soil (>2 mm)

Question 7. 
List 5 properties of sandy soil.
Answer:
Properties of sandy soil are :

1. The particle size is large.
2. They are difficult to shape.
3. They have good drainage properties.
4. They don’t absorb water well.
5. They dry well and are well aerated.

Question 8. 
What makes the northeastern plain so fertile?
Answer:
The northeastern plains of India are so fertile because of the abundant deposits of rich alluvial soil brought in by the rivers and tributaries flowing through it. This soil is the most fertile type of soil as it contains a mixture of sand, clay, silt and minerals directly washed down from the mountains. 

Question 9. 
Why do farmlands shimmer in the afternoon Sun?
Answer:
Farmlands shimmer in the afternoons due to the layer of water vapour coming out of the soil reflecting the sunlight.

Question 10. 
Why does masoor grow best in loamy soils?
Answer:
Loamy soils are very fertile and also possess good drainage properties. As lentils require soils which drain water easily, masoor. which is also a lentil, and grows best in loamy soils.

Question 11. 
Which type of areas are more affected by erosion?
Answer:
Desert or bare lands are more affected by erosion because these have very less vegetation.

Question 12. 
How erosion can be prevented?
Answer:
Erosion can be prevented 

1. by planting more trees.
2. by preventing deforestation and cutting of trees.

Long Answer Type Questions

Question 1. 
How can be soil profile observed? 
Answer:
The following methods can enable the observation of the soil profile in an area :

1. Observing the insides of a good pit dug.
2. Observing the sides of a hill road.
3. Going underwater and looking at the sides of a steep river bank.
4. During laying the foundation of a building.

Question 2. 
What are the different layers of soil called? List 3 properties associated with each of them.
Answer:
The different layers of soil are called horizons. There are 4 horizons, namely A-Horizon, B-Horizon, C-Horizon and Bedrock.

Horizon	Property
A-Horizon	(i) Topmost layer, also called topsoil. (ii) Rich in humus. (iii) Generally soft, porous and can retain more water.
B-Horizon	(i) the second layer from the top, also called the middle layer. (ii) Rich in mineral content. (iii) Generally harder and more compact.
C-Horizon	(i) Third layer from the top. (ii) Mainly consists of small lumps of rocks with cracks and crevices. (iii) Very little organic material is found in the layer.
BedRock	(i) Layer at the bottom. (ii) Forms the base of the water table. (iii) Difficult to reach or dig with a spade.

Question 3. 
Describe the soil type required for growing:

1. Wheat, 
2. Cotton, and 
3. Paddy. 

Answer:

Crops	Soil types
1. Wheat	Clayey soils are rich in humus, fertile and good at retaining water.
2. Cotton	Soils that are sandy-loam or loamy; have good drainage and are well aerated.
3. Paddy	Soils rich in clay and organic matter; have a good retention capacity.

Question 4. 
Explain an activity to show that soil contains moisture.
Answer:

1. Take a test tube. Put two spoons full of soil samples in it and heat it.
2. It is observed that as the soil gets heated, the moisture within it starts evaporating, rises and upon reaching the upper walls of the tube condenses to small water droplets.

Removing moisture from the soil.

1. It happens because the soil had some moisture which converted to vapour and as the upper part of the test tube was .cooler, it condensed back to the water.

Question 5.
Explain an activity to show that soil absorbs water.
Answer:

1. Take a plastic funnel and place a cone-shaped filter paper in it. 
2. Pour 50 g of powdered soil into the funnel and place the funnel over a beaker.
3. Measure a certain amount of water in a measuring cylinder and pour it drop by drop on the soil.
4. When water starts dripping, stop pouring further water.
5. To calculate the percentage of water absorbed by the soil, measure the amount of water left in the measuring cylinder.
6. Let the initial volume of water in the measuring cylinder is U mL = 100 mL
7. The amount of leftover water in the measuring cylinder is V mL.
8. The volume of water absorbed by the soil is (U - V) mL.
   
9. Since 1 mL of water weighs 1 gram.
10. The weight of water absorbed by the soil is (U - V) g = (100 - V) g.
11. Let the weight of soil is W g = 50 g.
12. The percentage of water absorbed by the soil is[(U-V)/W] x 100 = [(100-V)/50] x 100
13. Hence, we can observe now that sandy soils would have the highest percolation rate.