Ncert – Chapter – 9th – Soil
In this post we will see class 7th Science – Soil based on NCERT. It can be used for all the students studying in CBSE boards or any board which are using the NCERT books for their syllabus. All the answers are prepared by Expert teachers and are very useful for all the board using NCERT like CBSE, State boards.
you can check Previous Chapter Solutions here –
- NCERT Class 7th Science Chapter 1- Nutrition in Plants Solutions
- NCERT Class 7th Chapter 2nd solution – Nutrition in Animals – All Exercise Answers
- NCERT Solution Class 7th – Chapter 3 – Animal Fibre
- NCERT Solution Class 7th – Chapter 4th – Heat And Its Affect
Also Class 7th Science All chapters solutions here –
Exercise – 1st Answer In Brief
[1] What is weathering ?
Solution – The smaller piece due to breaking up of rocks into simpler substance over thousand of year is called weathering .
[2] What are the three major layer of the earth ?
Solution – There are three layers or soil horizon ; A – Horizon or topsoil B – Horizon or subsoil C – Horizon that consits of weatherd rock fragment .
[3] Name the main constituents of soil ?
Solution – The main constituent of soil are soil particle of different sizes , humus, air and water and his home to different living thing .
[4] What is humus ?
Solution – Humus is formed from the decayed remains of dead organsisms .
[5] How do earthworm increase soil fertility ?
Solution –Earth worm improve the texture of the soil by moving through the soil they open channels for root to grow into their action also help air to enter and the water drain from it .
[6] What is loam ?
Solution – Loam is a mixture of sandy and clayely soil it is very fertile and good for plants .
[7] When does the soil become waterbody ?
Solution – In ares where there is a lot of clay in the soil water stays stagnent above the soil when there is heavy rainfall the soil is then said to be waterlogged .
[8] What is a leaching ?
Solution – In areas where the soil particle are large as in sandy soil the water percolates though washing away all the nutrient with it this is called leaching .
Exercise – 2nd Answer in long
[1] Discuss the models of weathering ?
Solution – Physical weathering ;-
The kind of weathering where the nature of the soil is not changed is called physical weathering .
Biological weathering ;-
In this kind of weathering living organisms are the cause for the weathering .
Chemical weathering ; –
In chemical weathering chemical reaction between substance in the rock and the air or water result in the breaking up of the rock .
[2] Distinguish between topsoil and subsoil ?
Solution – Topsoil ;-
( A -horizon ) is the uppermost layer of the soil nearest to the surface it is dark layer where the roots of plant grow and other organisms live in it .It is formed by weathering & the activites of many organisms that live in it .
Subsoil ;-
( B -Horizon ) is the layer below the topsoil . it is lighter colured layer to grave stone and clay .
[3] Distinguish between sandy soil calyely and loany soil ?
Solution – Sandy soil ;-
Has mostly sand in it and very little silt and clay this soil is found in desert .
Clayely soil -;
Has mostly clay in it .
Loanly soil ;-
A combination of sandy and clayey soil gives a mixture called loan in loalnly soil the sand and clay particle stick together and form soil crumbs .
[4] Why is loam consisderd to be a good soil to grow plants ?
Solution – Because loam trap enough air for plants holds water without becoming waterlogged and is also easier to cultivate it is therefore ideal for growing plants .
[5] List the causes of oil erosion ?
Solution – Soil erosion is the removal of the topsoil by wind and water . it occur naturally all the time and thus causes the degredation of soil factors that cause erosion can be natural or human induval .
[1] Floods and heavy rains lossen the soil particle of weak soil .
[2] Drought result in the depletion of vegeation making it easier for rains and winds to carry away fine soil particle causing erosion .
[3] Due to deforation the soil get lossened as there are no roots to hold it together the soil losses its moixture is left exposed and gets eroded by wind and water .
[6] How ca n soil be conserved ?
Solution ;-
[1] Afforestation the planting of tree prevent soil erision .
[2] Terrace farming as done by build steps or flat rows called Terrace .
[3] Preventing overgrazing by animal can help prevent erosion .
[4] Building check dams to control flood also helps in conservating soil .
Exercise – 3rd Multiple Choice Question
[1] Which of these is not true about weathering ?
[1] Deforesation is used to prevent weathering .
[2] Roots of tree get into crevices and force the rock to break .
[3] diference in breaking up of rock .
[4] Weathering is caused by construction of roads ,
Answer – 1st and 4th
[2] The correct sequence of layers in a soil profile ( from bottom to up)
[1] Topsoil , Subsoil , and bedrock.
[2] Subsoil , Topsoil and bedrock .
[3] Bedrock , topsoil and subsoil .
[4] Topsoil , Bedrock and subsoil .
Answer – Topsoil , Subsoil and bedrock .
[3] Which of the following statement does not refer to topsoil ?
[1] It has no nutrients and it is a very hard layer .
[2] Plants grow in this layer and Most living organisms are present in this layer .
Answer – It has no nutrient and it is a very hard layer .
[4] Humus is an important part of soil because it _____
[1] Helps clay particle to stick together .
[2] Increase the ability of sand to hold water .
[3] Makes the soil fertile .
[4] Helps in nitrogen fixation .
Answer – Makes the soil fertile .
[5] Loam is a mixture of _____
[1] Sand and clay
[2] Sand and silt
[3] Clay and gravel
[4] Clay and silt
Answer – Sand and clay
[6] Which soil does wheat grow well in ?
[1] Sandy
[2] Clayely
[3] Loamy
[4] Dark
Answer – Loamy
[7] The percolation rate of the soil is ________
[1] The rate at which water enters and moves through the soil .
[2] The rate at which water is absorbed by the soil .
[3] The rate at which water evaporates from the soil .
[4] The rate at which the soil loses water .
Answer- The rate at which water enters and move through the soil .
[8] Water logging is common in soils that have _____
[1] Humus
[2] Clay
[3] Sand
[4] Lichens
Answer – Humus
[9] Which of these does not cause soil erosion ?
[1] Flood
[2] Drought
[3] Deforestation
[4] Afforestation
Answer – Afforestation
[10] Which of the following is not a threat to soil conservation ?
[1] Erosion
[2] Percolation
[3] Climate change
[4] Deforestation
Answer – Percolation
Exercise -4th Fill in the blanks
[1] The kind of the following where the nature of the soil is not changed id called _____ weathering ? { Physical}
[2] Decayed plant and animal matter is called ______ . { Humus}
[3] The A -Horizon is the _______ layer and is also known as _________ { Uppermost and topsoil }
[4] ________ is a soil horizon that has very little humus and so is not suitable for plant growth . { A- Horizon}
[5] The smallest soil particle are ________ Particle . { Clay}
[6] Drainage of water in _______ soil is very slow . { Clay}
[7] Rain water sinks into the soil and reaches the rocky layer to form the ________ { Water table }
[8] ______ Act as windbreakers and slow down the erosion of soil . { Tree }
[9] _________ farming is a method of preventing of soil erosion on mountain . { Terrace }
Exercise – 5th True or false
[1] Growing roots of tree can cause cracks in rocks . { True }
[2] Rainwater can cause weathering . { True }
[3] Since clay hold water clayely soil is very good for plants as they get plenty of water . { True }
[4] Humus is formed by the action of decomposers in soil . { False }
[5] Waterlogging is good for plants . { True }
[6] Floods and heavy rain can carry away soil . { True }
[7] Incorrect irrigation method can lead to soil erosion . { True }
you can check Previous Chapter Solutions here –
- NCERT Class 7th Science Chapter 1- Nutrition in Plants Solutions
- NCERT Class 7th Chapter 2nd solution – Nutrition in Animals – All Exercise Answers
- NCERT Solution Class 7th – Chapter 3 – Animal Fibre
- NCERT Solution Class 7th – Chapter 4th – Heat And Its Affect
- NCERT -Solution – Class 7th – Chapter 5 -Transfer in Heat
Also Class 7th Science All chapters solutions here –
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