CBSE Class 9 Science Revision Notes Chapter 14

CBSE Class 9 Science Revision Notes Chapter 14 – Natural Resources

In Class 9 Science Chapter 14 Notes, students will learn about the natural resources of the environment – land, air and water. In these Class 9 Chapter 14 Science Notes, students will learn that the air that surrounds the Earth and protects it from harmful radiation is known as the atmosphere. Chapter 14 Science Class 9 Notes are created by a team of experts to help students easily understand all the topics in the NCERT books. Extramarks provides the notes in PDF format, which students can download from the website.

The CBSE revision notes also include important questions prepared after thorough research on exam trends and paper patterns. Extramarks provides revision notes for all subjects in Class 9, which include important formulas and CBSE extra questions. Students can also download CBSE sample papers and CBSE past years’ question papers from the Extramarks website for daily practice. It will help them understand the exam pattern and develop time-management skills.

CBSE Class 9 Science Chapter 14 – Natural Resources Revision Notes 

Access Class 9 Science Chapter 14 – Natural resources in 30 Minutes

Chapter 14 Science Class 9 Notes: A Brief Overview

The main topics covered in Class 9 Science Chapter 14 Notes are rain, water and pollution, the greenhouse effect, biogeochemical cycles, the ozone layer, and ozone depletion. Class 9 Science Notes Chapter 14 will give students an in-depth understanding of rain and how it forms.

Rain

The process of condensation and water evaporation is called rain, which is caused by the water cycle. During the day, water bodies heat up and evaporate into the atmosphere, and the vapour cools as it rises. The vapour condenses into small water droplets that fall as rain due to precipitation. The existing wind patterns determine the rainfall patterns.

Acid Rain

Acid rain is caused by the release of various gases such as S02 and N02, which are emitted from fuels and vehicles. When dissolved in the rain, they form sulphuric and nitric acid.

Water

Water is a renewable resource, which is very important for the physiological activities of animals and plants. It is present in two forms: surface water and groundwater. The maximum amount of water available is salty marine water. The majority of the freshwater that exists on the planet is in the form of frozen ice. Both plant and animal cells require water to function. So, to survive, organisms must maintain the level of water bodies. The amount of water available determines the number of members of each species that may survive in a given area and the diversity of life there.

Soil

Soil is the uppermost layer of the crust, formed by the constant weathering of mountains. Certain factors causing soil formation include Organisms, Time and Climate. Soil is the combination of organic matter. Water, minerals, air, and inorganic matter are some of the soil’s essential components. Soil can be of various types, such as sand, loam, silt, and clay. The organic contents like twigs, dried leaves,  animal decomposition, and the remains of plants form the upper layer called humus. Humus plays a crucial role in raising the fertility rate of the soil.

Soil pollution refers to the addition of toxic or harmful chemicals, which causes it to become unproductive. Some primary causes of soil pollution are fertilizers, industrial wastes, acid rain, insecticide, accidental oil spills, etc. Another form of soil degradation is soil erosion. The primary agents that cause soil erosion include rainwater, wind, and rainwater. This results in a reduction of the crop production potential and a reduction of topsoil.   

Class 9th Chapter 14 Science Notes: Water Pollution

Water pollution means the introduction of unwanted elements into water bodies. Fertilisers, pesticides, sewage, chemicals, and detergents are some of its examples. When the water temperature rises due to pollution, the amount of dissolved oxygen decreases. Aquatic creatures receive oxygen from dissolved oxygen. The reduction of dissolved oxygen in the water causes the death of aquatic organisms.

Water pollution results from a change in the biological, chemical, and physical characteristics of water that negatively impacts aquatic life and renders the water unfit for use or consumption. The main reasons for water pollution are as follows:

• When desirable substances such as oxygen are removed from the water.
• A water temperature change.

Notes of Ch 14 Science Class 9: Greenhouse Effect

The presence of greenhouse gases in the atmosphere, such as methane, carbon dioxide, and nitrogen oxide, prevents heat from falling on the Earth and prevents it from being absorbed. As a result, it remains heated, and this phenomenon is known as the greenhouse effect. 

Some gases protect you from the earth’s warmth escaping. The “inexperienced residence effect” refers to the possibility that an increase in the concentration of certain gases in the atmosphere could increase global average temperatures. One of the less experienced household gases is CO2. An increase in the amount of CO2 in the atmosphere could lead to more heat being retained by the environment and lead to global warming.

Ozone Layer

The ozone layer is found in the stratosphere. Each molecule of ozone consists of 3 oxygen atoms. Despite being toxic, it helps keep harmful radiation from the earth’s surface, which can cause damage to human health. 

The three molecules of oxygen combine to create ozone, forming a layer in the stratosphere. It acts as a protective layer and prevents harmful radiation from reaching the Earth. When CFCs interact with ozone, they break it down, which causes ozone depletion.

Class 9 Ch 14 Science Notes: Biogeochemical Cycles

The biotic and abiotic elements of the biosphere interact to form a system, and such a flow results in the formation of a cycle known as a biogeochemical cycle. 

Some Of The Cycles Mentioned In The Ch 14 Class 9 Science Notes Are:

• Water Cycle 
• Nitrogen Cycle
• Carbon Cycle
• Oxygen Cycle

• Water Cycle

It is a process by which water evaporates and falls on the land as rain. The rainwater returns to the ocean with the help of rivers. The steps included in the water cycle are as follows:

• Evaporation
• Transpiration
• Respiration
• Precipitation

Water dissolves a large number of substances. Some soluble minerals dissolve in water as it passes through or over rocks. As a result, rivers transport a lot of nutrients from the land to the sea, where marine species utilise them. It can be understood with the diagram below:

Water cycle

• Nitrogen Cycle

The nitrogen cycle is the process through which nitrogen passes from the atmosphere to organisms and soil before returning to the atmosphere. The nitrogen cycle involves the following processes:

• Nitrogen Fixation
• Nitrification
• Ammonification
• Denitrification

The air in the Earth’s atmosphere is made up of approximately 78% nitrogen. The percentage of nitrogen within the environment is maintained by the nitrogen cycle. It is not easy for plants and animals to use atmospheric nitrogen. It must be constantly supplied through the means of a few organisms referred to as nitrogen fixers. Rhizobium, a nitrogen-solving microorganism, stays in symbiotic affiliation within the roots of leguminous plants. These microorganisms help convert atmospheric nitrogen into ammonia, which benefits the plants. 

Nitrogen-solving microorganisms and other residing microorganisms within the soil gain 90% of nitrogen fixation. When lightning occurs, high temperatures and pressures created within the air convert nitrogen into oxides of nitrogen. These oxides dissolve in water to offer nitric and nitrous acids and fall on land at the side of rain.

Plants then convert those nitrates and nitrites into amino acids. Ammonification is the technique where soil microorganisms decompose useless natural products and release ammonia into the soil. Nitrification is the technique by which ammonia is transformed into nitrites and nitrates. Denitrification is the technique by which nitrates are transformed into atmospheric nitrogen. A diagrammatic representation of the nitrogen cycle has been shown below:

Nitrogen cycle

• Carbon Cycle

The carbon cycle describes how carbon flows from the atmosphere to the earth. The carbon cycle involves the following processes:

• Photosynthesis 
• Respiration
• Decomposition
• Combustion

Carbon exists within the elemental shapes of diamonds and graphite. The carbon cycle first began to evolve in plants. Plants use carbon dioxide to synthesise glucose in the presence of sunlight through photosynthesis. 

Living matters exhaust those glucose molecules to supply strength and breathe carbon dioxide through respiration. Burning fuels for processes like heating, cooking, transportation, and commercial strategies provides carbon dioxide. A diagrammatic representation of the carbon cycle has been shown below:

Carbon cycle

• Oxygen Cycle

The oxygen cycle is the process through which plants absorb carbon dioxide from the environment and oxygen is released into the atmosphere. The oxygen cycle entails:

• Respiration
• Combustion
  • Photosynthesis

Three processes use up oxygen from the atmosphere, namely combustion, respiration, and the formation of nitrogen oxides. Photosynthesis is the most common process through which oxygen is returned to the environment. A diagrammatic representation of the oxygen cycle has been shown below: