Soil - Class 7 Chemistry - Extra Questions

How is clayey soil useful for crops?

Hint: Clay soil has a good water-retaining ability.

Explanation: 

Clay soil is useful for crops in the following ways:

  • It has a very fine size of soil particles due to which the water-retaining capacity is more than other types of soil.
  • It is rich in humus and is very fertile so it is used for growing wheat and gram.
  • It is rich in organic matter and provides suitable nutrients to the crops for growing purposes.



What are the various uses of soil?

Various uses of soil are:
  • The plants that are grown in soil can be used for food, clothing, recreation, aesthetics, building materials, medicines, etc
  • Soil has vital nutrients for plants.
  • Soil is an important part of the building process.
  • Clay soil is used in making pottery.
  • Soil is used in wastewater treatment plants.


What are the different types of soil?

Different types of soil are:
  1. Sandy soil
  2. Clayey soil
  3. Loamy soil
The soil is classified on the basis of the proportion of particles of various sizes. If soil contains a greater proportion of big particles it is called sandy soil. If the proportion of fine particles is relatively higher, then it is called clayey soil. If the amount of large and fine particles is about the same, then the soil is called loamy. 


Define soil profile and explain horizons with figure.

A vertical section through different layers of the soil is called the soil profile. The layers of the soil are referred as horizons.
  • The upper most horizon is very fertile and provides nutrients to plants. It is top-soil or A-horizon. 
  • The second layer below this is B-horizon. 
  • Third layer is C-horizon below.
  • Below the C-horizon is the bedrock which is hard and difficult to dig.

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What is meant by alluvial soil? What are its uses?

Rivers of north India which flow from the Himalayas, bring a variety of materials including silt, clay, sand, and gravel. They deposit their materials called alluvial soil, in the planes of north India.
This soil is very fertile and grows many crops and gives a very good yield.


Define loamy soil & its uses.

The best topsoil for growing plants is loam. Loamy soil is a mixture of sand, clay, and another type of soil particle known as silt. Silt occurs as a deposit in river beds. The size of the silt particles is between those of sand and clay. 
The loamy soil also has humus in it. It has the right water holding capacity for the growth of plants.
Uses of loamy soil
It has suitable for growing most varieties of plants. It is also used in construction in villages.


Classify the soil.

Soils are classified into three types on the basis of the proportions of particles of various sizes.
1) Sandy soil:- If soil contains a greater percentage of big particles then it is called sandy soil.
2) Clayey soil:- If the proportions of fine particles are relatively higher then it is called clayey soil.
3) Loamy soil:- If the amount of large and fine particles is about the same then it is called loamy soil.


What is the importance of good soil structure?

Soil structure basically refers to the type of constituents and the ratio in which they are present in the soil. The soil structure is important with respect to the growth of plants and the type of plantation which can occur in a particular area. Good soil structure has advantages like:
$$\cdot$$ Roots get a sufficient supply of oxygen
$$\cdot$$ It has good water drainage and thus roots grow well.
$$\cdot$$ It can reduce soil erosion caused by surface run-off.


How do you find out the absorption of water by soil?


Take a plastic funnel. Take a fliter paper (or a piece of newspaper sheet), fold and place it as shown in the figure. 

Weigh $$50\,g$$ of dry, powdered soil and pour it into the funnel. 

Measure a certain amount of water in a measuring cylinder and pour it drop by drop on the soil. 

You can use a dropper for this purpose. Do not let all the water fall at one spot.

Pour water all over the soil. Keep pouring water till it starts dripping. Subtract the amount of water left in the measuring cylinder from the amount you started with. 

This is the amount of water retained by the soil. Record your results in your notebook in the following manner:

Weight of soil = $$50\,g$$

Initial volume of water in the measuring cylinder = U mL

Final volume of water in the measuring cylinder = V mL

Volume of water absorbed by the soil = $$(U - V)mL$$

Weight of water absorbed by the soil = $$(U - V)\,g$$

($$1\,mL$$ of water has weight equal to $$1\,g$$)

Percentage of water absorbed

$$= \dfrac{(U - V)}{50}\times100$$

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What is soil should be taken to prevent it?

Soil erosion  - The removal of the topmost fertile layer of the soil by wind and water is known as soil erosion, Soil conservation is essential to protect soil from erosion. following measures must be implemented stop soil erosion : 
 1. Afforestation must be done on large scale to protect fertile soil from erosion.
2. Natural forests must be conserved.
3. While crop harvesting, roots must be left in the soil.
4. Bio fencing must be done around the field.


Match the items in Column I with those in Column II


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How soil can be classified ? Name them.

  • The soil is classified on the basis of the proportion of particles of various sizes. 
  • If soil contains a greater proportion of big particles. It is sandy soil.
  • If the proportion of fine particles is relatively higher then it is clayey soil.
  • The best topsoil for growing plants is loamy soil.


Fill in the blank:

The soil layers are referred as _________.

The soil layers are referred as $$\underline{horizons}$$. Each horizon is different in texture, colour, chemical composition and depth.


What is loam soil?

The soil containing $$34\%$$ air, $$66\%$$ water along with humus is called loam soil. It is best for the crops.


List the differences between clayey soil and sandy soil.

 Clay soil Sandy soil
 The proportion of fine particles is higher. The proportion of large particles is higher.                                       
 Particles are packed tightly.   Particles are loosely packed.
 It can hold a good amount of water.    The ability to retain water is low.
 Water cannot drain quickly.  Water can drain quickly.
 It is heavy in weight. It is light in weight.
                                                                               
    
                         
              
                           

                                        




Which soil is considered as best soil for most of the crops? What is its composition?

Loamy soil contains large and fine size particles in about the same proportion Or it is a mixture of sand, clay, and silt. The size of silt particles is between sand and clay. Silts occur as deposits in riverbeds. 
Loamy soil has the right water holding capacity for the growth of the plants and also contains humus which is very important for plant growth hence it is the best soil for most crops.


Class 7 Chemistry Extra Questions