CBSE Class 7 Science Exemplar Chapter 9: Soil NCERT Solutions
This chapter delves into the fundamental aspects of soil, a crucial component of our environment. The NCERT Solutions for Class 7 Science Exemplar Chapter 9 provide a detailed exploration of soil, covering its formation, composition, and the various types of soil. Students will learn about the different layers of soil, the properties of various soil types like sandy, loamy, and clayey soils, and the importance of soil for plant life and ecosystems. The solutions also highlight the significance of soil conservation and the measures needed to protect this vital resource from erosion and degradation. These solutions are designed to help students grasp complex concepts through clear explanations and step-by-step problem-solving, aiding in effective exam preparation and a deeper understanding of environmental science.
Quick info
| Board | CBSE |
|---|---|
| Class | Class 7 |
| Subject | Science Exemplar |
| Session | 2026 |
| Language | English |
| Type | NCERT Solutions |
| Chapter | Chapter 9 |
Chapter summary
Chapter 9 of the Class 7 Science Exemplar focuses on Soil. The NCERT Solutions cover the composition of soil, including different particle sizes like clay, silt, and sand, and the role of humus. It explains the characteristics of various soil horizons and types, such as sandy, loamy, and clayey soils, emphasizing their water retention and percolation properties. The solutions also address the importance of soil conservation and the factors influencing soil formation.
Learning outcomes
- Understand the composition and formation of soil.
- Differentiate between various soil horizons and types.
- Explain the properties of sandy, loamy, and clayey soils.
- Recognize the importance of soil conservation.
- Arrange soil particles by size.
- Identify the components of loamy soil.
Topics covered
Paper topics
- Soil Composition
- Soil Formation
- Soil Particles (Gravel, Sand, Silt, Clay)
- Soil Horizons (A-horizon, B-horizon, C-horizon)
- Types of Soil (Sandy, Loamy, Clayey)
- Properties of Soil (Water absorption, percolation)
- Humus
- Soil Conservation
- Factors Affecting Soil
- Microorganisms in Soil
Important topics
- Soil Composition and Particle Size
- Properties of Sandy, Loamy, and Clayey Soils
- Role of A-horizon and Humus
- Soil Conservation Measures
- Understanding Soil Formation Processes
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Questions and Solutions
Multiple Choice Questions
1. The microorganisms present in the soil require moisture (water) and nutrients for growth and survival. Choose from the options below the habitat (place) where the soil has plenty of water and nutrients.
- Desert
- Forest
- Open field
- Cricket ground
Solution: The correct option is (b) Forest.
Explanation: Forests are characterized by a dense cover of trees and other vegetation. This leads to a significant amount of decaying organic matter (humus) on the forest floor, which enriches the soil with nutrients. The trees also help in retaining moisture from rainfall, keeping the soil moist. This combination of ample nutrients and moisture creates an ideal habitat for a large population of microorganisms to thrive.
2. Availability of water and minerals in the soil for maximum absorption by roots is in the –
- B-horizon
- C-horizon
- A-horizon
- surface of soil
Solution: The correct option is (c) A-horizon.
Explanation: The A-horizon, also known as the topsoil, is the uppermost layer of the soil. It is typically rich in humus, making it dark in color, porous, and soft. These characteristics allow it to absorb and retain a significant amount of water and minerals, which are then readily available for plant roots to absorb for their growth and survival.
3. Soil conservation measures are mainly aimed at protecting which of the following?
- Plants
- Top soil
- Sub soil
- Soil organisms
Solution: The correct option is (b) Top soil.
Explanation: Top soil is the most fertile layer of the soil, containing the highest concentration of humus and essential nutrients derived from decaying organic matter. It is vital for plant growth. Soil conservation measures are primarily designed to prevent the erosion and degradation of this precious topsoil, thereby preserving its fertility and productivity for agriculture and maintaining healthy ecosystems.
4. Read the following statements with reference to soil:
(i) Weathering is a very fast process of soil formation.
(ii) Percolation of water is faster in sandy soils.
(iii) Loamy soil contains only sand and clay.
(iv) Top soil contains the maximum amount of humus.
Choose the correct statements from the above.
(a) (ii) and (iv)
(b) (i) and (iii)
(c) (ii) and (iii)
(d) (i) and (ii)
Solution: The correct option is (a) (ii) and (iv).
Explanation:
Statement (i) is incorrect because weathering, the process of breaking down rocks to form soil, is generally a very slow process that takes thousands of years.
Statement (ii) is correct. Sandy soils have large particles with large spaces between them, allowing water to drain through quickly, meaning percolation is faster.
Statement (iii) is incorrect. Loamy soil is a mixture of sand, silt, and clay, along with humus. It is not composed solely of sand and clay.
Statement (iv) is correct. The topsoil (A-horizon) is the layer richest in humus, which is decomposed organic matter, providing essential nutrients for plants.
Very Short Answer Questions
5. Soil has particles of different sizes. Arrange the words given below in increasing order of their particle size.
Rock, Clay, Sand, Gravel, Silt
Solution: The words arranged in increasing order of particle size are:
Clay < Silt < Sand < Gravel < Rock
Explanation: Clay particles are the smallest, followed by silt, then sand. Gravel consists of larger fragments, and rocks are the largest solid masses from which these particles originate.
6. The components of loamy soil are _____, ____ and _____.
Solution: The components of loamy soil are Sand, Silt, and Clay.
Explanation: Loamy soil is considered ideal for plant growth because it is a balanced mixture of sand, silt, and clay. This composition provides good drainage, aeration, and water retention, along with sufficient nutrients from the organic matter present.
Common mistakes
- Confusing the speed of soil formation (weathering).
- Incorrectly assuming loamy soil contains only sand and clay.
- Misidentifying the most fertile soil horizon.
- Underestimating the importance of topsoil protection.
Revision tips
- Focus on understanding the properties of different soil types.
- Memorize the order of soil particle sizes from largest to smallest.
- Review the functions of each soil horizon, especially the A-horizon.
- Understand why soil conservation is critical and what measures are taken.
Practice MCQs
Q1. Which habitat is most likely to have soil with plenty of moisture and nutrients for microorganisms?
Explanation: Forests typically have abundant organic matter (humus) from decaying plants and animals, providing rich nutrients. The dense canopy also helps retain moisture, creating a moist environment suitable for microorganisms.
Q2. The soil layer where roots can absorb the maximum amount of water and minerals is:
Explanation: The A-horizon, or topsoil, is the most fertile layer. It is porous, soft, and rich in humus, which allows for better absorption and retention of water and minerals essential for plant growth.
Q3. Soil conservation efforts are primarily focused on protecting which part of the soil?
Explanation: The topsoil is the most fertile layer, containing humus and essential nutrients for plant growth. Protecting the topsoil is crucial for maintaining soil fertility and preventing erosion.
Q4. Which of the following statements about soil are correct?
Explanation: Statement (ii) is correct because sandy soils have larger particles and larger pore spaces, allowing water to percolate faster. Statement (iv) is correct as the topsoil (A-horizon) is rich in humus. Weathering is a slow process, and loamy soil is a mixture of sand, silt, and clay.
Frequently asked questions
What is soil and how is it formed?
Soil is the uppermost layer of the Earth's crust, composed of mineral particles, organic matter, water, and air. It is formed through a slow process called weathering, where rocks are broken down by physical, chemical, and biological agents over long periods.
What are the main components of soil?
The main components of soil are mineral particles (derived from rocks), organic matter (humus from decaying plants and animals), water, and air. Soil also contains living organisms like microorganisms and earthworms.
What are the different types of soil mentioned in Class 7 Science?
Class 7 Science discusses three main types of soil: sandy soil (large particles, good aeration, poor water retention), clayey soil (fine particles, poor aeration, good water retention), and loamy soil (a mixture of sand, silt, and clay, considered ideal for plant growth).
Why is the A-horizon important?
The A-horizon, also known as topsoil, is the most fertile layer. It is rich in humus and nutrients, making it crucial for plant growth. It is also porous and helps in water absorption.
What is soil conservation and why is it necessary?
Soil conservation refers to the practices used to protect the soil from erosion and degradation. It is necessary because soil is a finite resource essential for agriculture, supporting plant life, and maintaining ecosystems. Protecting the topsoil is a key aspect of conservation.
How do these NCERT Solutions help in exam preparation?
These solutions provide clear, step-by-step explanations for all questions, including MCQs and short answer types. They clarify concepts, reinforce learning, and help students understand the methods to solve problems related to soil, making exam revision more effective.
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