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Class seven science soil Long answers questions
Chapter 9: Soil
Long Answer Type Questions
1. Let’ assume, if your teacher took you to the school lab and showed you the same activity which is written in your NCERT book (i.e. activity 9.6.) Now, he asked you to measure the percentage of water, absorbed by the soil. (If, 1ml of water has a weight equal to 1g) He gave you some information related to the activities which are as follows:
The initial volume of water in the measuring cylinder = 150 mL
The final volume of water in the measuring cylinder = 75 mL
Weight of soil = 300 g
Answer:
Percentage of water in soil =
Soil absorbed 25 per cent water.
2. A. Explain soil and how is it formed? B. Explain each component present in the soil.
Answer: A. Soil is the uppermost layer of the earth’s crust. It is a mixture of tiny rock particles and humus. Usually, it is brown in colour. It is very essential for every living being.
B. If we pour the soil into the water, we can easily observe each component of soil, which are as follows:
i. Humus: It is a layer of dead and decaying materials.
ii. Water: The moisture of the soil is water.
iii. Clay: This layer contains very fine particles, almost in a powdered form.
iv. Sand: Sand particles are larger than clay particles.
v. Gravel: They are the largest particles mixed in the soil.
3. How many forms of soil are found in the layers of the earth? Describe each one of them in detail.
Answer: Soil is categorised according to the size and quantity of the substances present in the soil. It is divided into the following three types:
1. Clayey soil: This type of soil is made up of the finest particles in almost a powdered form. It contains very little amount of humus. Its fine particles are packed very tightly with very fewer air gaps. Due to this nature, it holds the water in a good amount and makes the soil sticky. Because of its sticky nature, it is used to make toys, decorative items, bricks, etc.
2. Sandy soil: The particles present in this soil are higher than that of clayey soil, but it does not contain humus at all, that means that there are no minerals. Because of the big particles, there are large spaces between them. Due to this nature, it is not able to hold water at all. It makes the soil dry, aerated and light in weight.
3. Loamy soil: This soil is a mixture of sandy soil, clayey soil and silt. It is the best soil for farming, as it contains a balanced quantity of humus, air space and moisture. The size of the silt particles is between sand and clayey soil particles.
4. What is the percolation rate? How do you assess the percolation rate of water in the soil?
Answer: The downward movement of water through the soil is called percolation. Percolation rate is the amount of water which is percolated by the soil in one minute. We can calculate it by using the following formula:
Percolation rate of water in soil =
5. What is the relationship between soil and plants and how different soil types are responsible for growing different types of crops?
Answer: There is no life on earth without soil because plants grow on soil. Not only do they take nutrition and water from the soil, but it also holds the plants tightly to the ground. Different types of soil support the growth of different types of crops depending on the number of minerals present in each soil type. 1. Loamy soil is a combination of sandy soil, clayey soil and silt, so it is the best soil type for growing a variety of crops. It supports the growth of cereals and pulses.
2. Clayey soil is good to hold water in large quantity, so it is good for paddy.
3. Sandy soil is usually known to be good for growing cotton.
6. Differentiate between sandy soil and clayey soil.
Answer:
Multiple Choice Questions
1. There are all the substances present in a moist soil given below in decreasing order. Read the order carefully and identify the
type of soil. Humus, minerals, water, rock particles
a. Loamy soil
b. Sandy soil
c. Clayey soil
d. None of them
2. All particles present in soil have different sizes. Which of the following is correctly arranged in the increasing order of their sizes?
a. Sand, clay, gravel, silt
b. Gravel, silt, sand, clay
c. Clay, silt, sand, gravel
d. Silt, clay, sand, gravel
3. To convert the acidic soil into neutral soil, what should be added to the soil?
a. Slacked lime solution
b. Quick lime solution
c. Fresh lime solution
d. Both a and b
4. Tick the correct unit of mass.
a. Gram
b. Kilogram
c. Both a and b.
d. None of them
5. Read each of the statements carefully and then identify the wrong statement/ statements:
A. Loamy soil is good to grow paddy.
B. Percolation rate is the amount of water percolated by soil per minute.
C. The components present in the soil get arranged according to their sizes and weight in a glass filled with water. This arrangement is called a soil profile.
D. Polythene bags spoil the fertility of the soil.
E. Soil is a mixture of rock particles and humus.
a. A and B.
c. C and D
b. A and C
d. D and E
6. What was another substance mixed by Leeladhar Dada in soaked soil before making pots?
a. Cow dung
c. Horse dung
b. Cement
d. Dry leaves
7. If you have samples of soils collected from the following areas which one would contain the highest number of microorganisms?
a. Forest soil
b. Sandy soil
c. Soil from your school’s cricket ground
d. Soil collected from road dust
8. Tick the most appropriate reason for soil erosion.
a. Heavy rain
b. Wind
c. Cutting down of trees
d. Burying dry leaves
9. Which type of soil has the highest rate of percolation?
a. Sandy soil
c. Loamy soil
b. Clayey soil
d. None of them
10. What will be the percolation rate in a soil sample that takes 36 minutes for 432 mL water to percolate?
a. 11 mL/min
c. 15 mL/min
b. 12 mL/min.
d. 36 mL/min
Answer: a 2. c 3. d 4. C 5. b 6. c 7. a 8. C 9. a 10. B