CBSE Class 7 Science Revision Notes Chapter 9

CBSE Class 7 Science Revision Notes Chapter 9 – Soil

Soil, air, and water are the three essential natural resources without which, life could not have flourished on Earth. The topic of soil is introduced to students in Class 7 Science Chapter 9 as per the CBSE Syllabus. This chapter is important from the exam perspective, but moreover, students must have a fair understanding of the chapter as it deals with one of the major elements of nature vital for the existence of human beings.

Extramarks provides extensive study materials that students can refer to to prepare for the exams. Class 7 Science Chapter 9 Notes provided by Extramarks discuss every topic related to soil in-depth. Students can easily understand all of the concepts and score better on the final exams.

In the Class 7 Science Chapter 9 Notes, students will learn about soil, its nature, formation, types, and uses of soil
Class 7 Chapter 9 Science Notes are easily available from the website. Therefore, students can access them at their convenience. 

Revision Notes For CBSE Class 7 Science Chapter 9

Access Class 7 Science Chapter 9 – Soil

Soil

• Soil can be defined as the unconsolidated material on the earth’s surface that forms most parts of the land.
• Soil consists of several organic and inorganic components which support plant growth that is essential for life on the earth.
• The physical and chemical properties of soil vary from region to region.

Soil Formation

• Soil is originally formed from hard rocks that disintegrated by the process of weathering or natural erosion over time.
• The conditions that influence the disintegration of rocks influence the properties of soil as well. 
• Some of the main processes of soil formation are as follows:

• Physical Weathering: This is the process of breaking down large solid rocks into small pieces and finally reducing them into rock particles without changing their chemical properties. Temperature, heat, pressure, etc. cause the weathering of big rocks. The physical forces that constantly change the volume of rocks and cause them to break are the sun and the wind.
• Chemical Weathering: In this process, rainwater reacts with the minerals present in rocks and produces new compounds or salts. Thus, rainfall changes the chemical properties of the rock and causes its disintegration.
• Biological Weathering: This process involves living organisms including plants, animals, and microbes that live on the rocks and disintegrate them by releasing acid from their bodies on the rock surface.

Soil Profile

Soil forms the uppermost layer of the earth’s surface but it itself has several layers known as soil horizons. The soil profile is the vertical cross-section of the soil of a given place from its topmost layer to the deepest point, where the underlying bedrock can be seen ultimately.

The layers commonly found in the soil are:

• Humus
• Topsoil
• Subsoil
• Parent material
• Bedrock

Types Of Soil

Soil can be broadly divided into three categories, namely – sandy soil, clayey soil, and loamy soil.

• Sandy Soil

• Sand makes up the majority of this soil.
• This soil is light, dry, warm and often acidic in nature.
• The diameter of the soil particles falls somewhere between 0.2mm and 2.0mm.
• As the soil contains more sand and less clay, it is lightweight.
• Because of the pores, the soil cannot contain water or any element in it for a long period of time. The nutritious elements, thus, get washed away from it with water. Therefore, sandy soil contains fewer nutritious elements in it. Though this soil is not ideal for agriculture, some plants can be grown on it by adding organic compounds to it.
• This kind of soil is very easy to work with.

• Clayey Soil

• This type of soil contains more organic matter and is heavy. It is ideal for plant growth.
• Clayey soil can hold water for a long time, hence, water does not drain easily through it.
• They remain moist and cold during the winter, but as the summer comes, they become dry and warm.
• Over twenty-five types of clay can be found in clayey soil.

• Loamy Soil

• This soil is a mixture of both sandy soil and clayey soil, which reduces their negative effects.
• It is preferred by gardeners as they can control the amount of water in it by mixing sandy soil and clayey soil in the desired ratio.

Uses of Soil

The various properties of soil make it suitable for various purposes.

• Agriculture: Plants spread their roots in the soil and hold it tightly so that they do not get uprooted easily. Further, they absorb water, minerals, and other elements from the soil for their nourishment.
• Building: Soil is extensively used in brick factories. It is given proper shape and size, then burnt in the fire to produce the red bricks needed for constructing large buildings.
• Pottery: Soil is also essential for artistic pursuits as well. Clay soil is mixed with water to make pots, bowls, ceramic vases, various room decors, sculptures, idols of gods, etc.
• Medicine and Beauty Products: Soil is home to many microorganisms. Some of them help fight harmful bacteria, so they are widely used in the pharma industry, especially for preparing antitumour drugs and medicines for tuberculosis. They are also used in various cosmetics. For example, skin ointments.

Soil Chapter Class 7 Notes

Extramarks’ Chapter 9 Science Class 7 Notes are meticulously designed by subject matter experts. These comprehensive notes give an overview of the entire chapter in a well-structured manner with suitable headers and subheaders to highlight all the major concepts. The summary of the notes is as follows.

The notes provide a general idea of the soil at first. Soil is a mixture of minerals, organic components and other living organisms that covers the upper surface of the earth’s crust. The notes then describe how soil is formed from the small rock particles disintegrated from the parent rocks, followed by a description of the soil profile and its types.

These notes will help students remove all doubts and feel more confident in their exam preparation. By examining these notes, students will be able to score better marks in the final exams.