CBSE Class 7

On this page, you will find NCERT Class 7 Geography Chapter 1 Notes Pdf free download. CBSE Class 7 Social Science Notes Geography Chapter 1 SST Environment will seemingly help them to revise the important concepts in less time.

Environment Class 7 Notes Social Science Geography Chapter 1

CBSE Class 7 Geography Chapter 1 Notes Understanding The Lesson

1. Environment is our basic life support system. It provides the air we breath, the water we drink, the food we eat and the land where we live.

2. Human beings modify to the natural environment by several means.

3. The place, people, things and nature that surround any living organism is called environment. It is a combination of natural and human made phenomena.

4. The natural environment refers to both biotic and abiotic conditions existing on the earth while human environment reveals the activities, creations and interactions among human beings.

5. The word ‘biotic’ is referred to living organizations such as plants and animals while non-living elements are called ‘abiotic’.

6. Land, water, air, plants and animals comprise the natural environment.

7. Lithosphere is the solid crust or the hard top layer of the earth. It is made up of rocks and minerals and covered by a thin layer of soil.

8. Lithosphere is an irregular surface with various landforms such as mountains, plateaus, plains, valleys, etc.

9. Lithosphere is the domain that provides us forests, grasslands, agricultural land and human settlements. It is also a source of mineral wealth.

10. Hydrosphere is domain of water. It comprises various sources of water such as rivers, lakes, seas, oceans, etc. It is essential for all living organisms.

11. The atmosphere is the thin layer of air that surrounds the earth. The gravitational force of the earth holds the atmosphere around it. It protects us from the harmful rays and scorching heat of the sun. It consists of a number of gases, dust and water vapour. The changes in the atmosphere produce changes in the weather and climate.

12. All plants, animals and human beings depend on their immediate surroundings and also interdependent on each other. Relation between the living organisms, as well as the relation between the organisms and their surroundings form an ecosystem.

13. Early men adapted themselves to the natural surroundings and led a simple life. All needs were fulfilled from the nature around them. But, presently human beings interact with the environment and modify it according to their needs.

On this page, you will find Wastewater Story Class 7 Notes Science Chapter 18 Pdf free download. CBSE NCERT Class 7 Science Notes Chapter 18 Wastewater Story will seemingly help them to revise the important concepts in less time.

CBSE Class 7 Science Chapter 18 Notes Wastewater Story

Forests: Our Lifeline Class 7 Notes Understanding the Lesson

1. Rich in lather, mixed with oil, black-brown water that goes down the drains from sinks, showers, toilets, laundries is dirty. This is called wastewater.

2. The suspended impurities in water are called contaminants.

3. The waste water released by homes, industries, hospitals and other users is called sewage.

4. ‘Cleaning of water’ is a process of removing pollutants before it enters a water body or is reused. This pro­cess is generally known as ‘sewage treatment’.

5. Sewage treatment plant is constructed to make wastewater or sewage reusable.

6. A complete network of sewers underlying the surface is planned to collect and send the wastewater for treatment. This is called sewerage system.

7. Treatment of wastewater involves physical, chemical and biological processes, which removes physical, chemical and biological matter that contaminates the wastewater.

8. The treated water from sewage treatment plant has a very low-level organic material and suspended matter. This is discharged into the water bodies by sometimes disinfecting with chlorine and ozone.

9. By-products of wastewater treatment are sludge and biogas.

10. Where underground sewerage systems and refuse disposal systems are not available, the low-cost on-site sanitation system can be adopted.

11. Open drain system is a breeding place for flies, mosquitoes and organisms which cause diseases.

12. We must realise our responsibility in maintaining the water sources in a healthy state. Adopting good sanitation practices should be our way of life.

Class 7 Science Chapter 18 Notes Important Terms

Aeration: It is the process in which air is pumped into clarified water to help bacteria grow.

Aerobic bacteria: Bacteria that require oxygen to live and grow are called aerobic bacteria.

Anaerobic bacteria: Bacteria that can survive without oxygen are called anaerobic bacteria.

Biogas: It is a gaseous fuel produced by the fermentation of manure, plant, or crop waste under anaerobic conditions which is used to generate electricity from waste matter.

Contaminants: There are harmful substances dissolved and suspended as impurities in water.

Sanitation: The proper disposal of sewage and garbage from the houses or nearby areas is called sanitation.

Sewage: Wastewater generated by homes, offices, hospitals, industries and other areas is called sewage.

Sewer: A network of big and small pipes to carry wastewater to treatment plant is called sewer.

Sewerage: It is the drainage system of sewer.

Sludge: Sludge is the residual, semi-solid material that is produced as a by-product during sewage treat­ment of industrial or municipal wastewater.

Wastewater: The water that is not fit for use is called ‘wastewater’.

On this page, you will find Forests: Our Lifeline Class 7 Notes Science Chapter 17 Pdf free download. CBSE NCERT Class 7 Science Notes Chapter 17 Forests: Our Lifeline will seemingly help them to revise the important concepts in less time.

CBSE Class 7 Science Chapter 17 Notes Forests: Our Lifeline

Forests: Our Lifeline Class 7 Notes Understanding the Lesson

1. A large area of land covered mainly with trees and other plants is called a forest.

2. Forest is a system comprising various plants, animals and microorganisms.

3. The type of animals and kind of trees differ from forest to forest.

4. Forests are the habitat of a large number of different kinds of animals, birds, reptiles, etc.

5. There are four layers of forest named as emergent layer, canopy, understorey and forest floor.

6. In a forest, trees form the uppermost layer, followed by shrubs. The herbs form the lowest layer of vegetation.

7. Based on the life span of plants and trees, they are classified as annuals, biennials and perennials. The organisms which make their own food from carbon dioxide and water in the presence of sunlight and chlorophyll are called producers.

8. The organisms which consume the food made by the producers are called consumers.

9. The organisms which derive their food items from the dead and decaying animals or plants are called decomposers.

10. Plants and animals in a forest depend on each other for many things.

11. In the forest, there is interaction between soil, water, air and living organisms.

12. All plants and animals are linked together by the process of eating and being eaten. This is called a food chain. Many food chains are interlinked to form a food web.

13. Importance of forests are:

• It help in replenishing groundwater.
• It regulate climate, and help rainfall.
• It purify the air and control air pollution.
• It control floods.

14. Forests are also called green lungs because plants release oxygen during photosynthesis which helps in keeping the balance of carbon dioxide and oxygen in the atmosphere.

15. The forest harbours variety of plants, thus providing greater opportunities for food and habitat for the herbivores which in result increases the availability of food for carnivorous animals. That is why, forest is a dynamic living entity.

16. The cutting down of forest trees for personal as well as for commercial purpose is called

17. Deforestation can lead to soil erosion, water pollution, disruption in water cycle, drought, global warming, etc.

18. We must preserve our forest.

Class 7 Science Chapter 17 Notes Important Terms

Canopy: The branches of tall trees of the forest form overhanging covering like a roof over the other plants in a forest. This is called canopy.

Crown: The branchy part of the tree above the stem is known as the crown.

Decomposers: The organisms which derive their food from the dead and decaying animals or plants are called decomposers.

Deforestation: The cutting down of forest for personal or commercial purposes is called deforestation.

Humus: Microorganisms feed upon the dead plants and animal tissues and convert them into a dark coloured substance called humus.

Regeneration: Regeneration is the process of renewal, restoration and growth of new organisms or the existing organisms in an area.

Seed dispersal: The transportation of seeds from the place of their origin to faraway places through vari­ous agents is called seed dispersal.

Soil erosion: The phenomenon of washing away of the top fertile layer of soil by water, or wind is called soil erosion.

Understorey: Understorey is an underlying layer of vegetation, specifically, the vegetative layer an especially the trees and shrubs between the forest canopy and the ground cover.

On this page, you will find Water: A Precious Resource Class 7 Notes Science Chapter 16 Pdf free download. CBSE NCERT Class 7 Science Notes Chapter 16 Water: A Precious Resource will seemingly help them to revise the important concepts in less time.

CBSE Class 7 Science Chapter 16 Notes Water: A Precious Resource

Water: A Precious Resource Class 7 Notes Understanding the Lesson

1. Water is the most important compound for all living things. There can be no life without it.

2. 22 March is celebrated as the world water day to attract the attention of everybody towards the importance of conserving water.

3. Water is an universal solvent.

4. 71% of earth surface is covered with water.

5. Three forms of water are solid, liquid and gas.

6. The water on the earth has been maintained for millions of years by various processes which make the water cycle.

7. The solid form of water, snow and ice, is present as ice caps at the poles of the earth, snow-covered mountains and glaciers.

8. Liquid water is present in oceans, lakes, rivers and even underground.

9. The gaseous form of water is the water vapour which is present in the air around us.

10. The rainwater or the water from other sources like ponds, lakes, etc., percolates under the ground and collects over the impermeable rocks. This water is called

11. The upper limit of underground water is called water table. The water table varies from place to place, and it may even change at a given place.

12. The process of seeping of water into the ground is called The groundwater gets charged by this process.

13. Aquifer is a water trap where groundwater is trapped between the layers of hard rock below water table.

14. Following are the causes of water shortage:

• Increasing population
• Rapid growth of industries
• Growing irrigation requirements
• Increasing agricultural activities
• Mismanagement

15. The distribution of water is also quite uneven due to number of factors. There are some regions in our country may have floods while others may suffer droughts at the same time.

16. Water management should be done by following ways:

17. Unnecessary use of water and overdrawing of groundwater should be stopped.

18. Recharge of groundwater must be increased through various processes.

19. We should prevent the wastage of water during its supply through pipes, the leaking taps in buildings and other places.

20. Plants wilt and ultimately dry-up if they are not watered for few days.

Class 7 Science Chapter 16 Notes Important Terms

Aquifer: A water trap where groundwater is trapped between the layers of hard rock below water table.

Depletion: Depletion is reduction in number or quantity of something. Rapid growth of industries, increasing population, growing irrigation requirements and mismanagement are some of the causes for water depletion.

Drip irrigation: It is a technique of irrigation by using narrow tubings which deliver water drop by drop directly at the base of the plant.

Groundwater: The water that seeps into the earth, gets collected between the layers of rocks and found below the water table is called groundwater.

Infiltration: The process of seeping of water into the ground is called infiltration. The groundwater gets recharged by this process.

Water harvesting: The water harvesting simply involves collection of rainwater from surfaces that can be used to recharge the groundwater or storing it for later use.

Water table: The water present deep under the ground is known as groundwater and the upper limit of this layer is known as water table.

On this page, you will find Light Class 7 Notes Science Chapter 15 Pdf free download. CBSE NCERT Class 7 Science Notes Chapter 15 Light will seemingly help them to revise the important concepts in less time.

CBSE Class 7 Science Chapter 15 Notes Light

Light Class 7 Notes Understanding the Lesson

1. Light is a form of energy which enables us to see objects from which it comes or from which it is reflected.

2. The objects which emit light of their own are known as luminous objects, g., the sun, lamp, candle, etc.

3. The objects which do not emit light of their own are known as non-luminous objects, g., chair, table, window, etc.

4. Light always travels in a straight line and this property of light is called rectilinear propagation of light.

5. Light falls on the surface of an object and the object sends the light back. This process of sending back the rays of light which fall on the surface of an object is called reflection of light.

6. The ray of light which falls on an object is called incident ray and the ray of light which is sent back by an object is called reflected ray.

7. A highly polished surface which is smooth enough to reflect a good fraction of light incident on it is called mirror.

8. An optical appearance produced by light or other radiations from an object reflected in the mirror or re­fracted through a lens is called

9. The image which can be formed or obtained on the screen is called a real image.

10. The image which cannot be obtained on the screen is called a virtual image.

11. The image formed by a plane mirror is erect, virtual and of the same size as the object.

12. Those mirrors whose reflecting surfaces are spherical or curved are called spherical mirrors.

13. There are two types of spherical mirrors:

• Concave mirror
• Convex mirror

14. When the reflecting surface of the spherical mirror is curved inwards, then it is called concave mirror.

15. A concave mirror can form a real and inverted image. When the object is placed very close to the mirror, the image formed is virtual, erect and magnified.

16. When the reflecting surface of the spherical mirror is curved outwards, then it is called convex mirror.

17. A convex mirror form erect, virtual, smaller size image of the object.

18. Lens is a piece of glass or transparent material with curved sides.

19. A lens that is thicker in the middle and thinner at the edges is called a convex lens. It is also known as magnifying glass.

20. A convex lens can form real and inverted image. When the object is placed very close to the lens, the image formed is virtual, erect and magnified.

21. A lens that is thinner in the middle and thicker at the edges is called a concave lens.

22. A concave lens always forms erect, virtual and smaller image than the object.

23. White light is composed of seven colours. These are red, orange, yellow, green, blue, indigo and violet (acronym: VIBGYOR).

Class 7 Science Chapter 15 Notes Important Terms

Concave lens: It is also known as diverging lens. It is thinner at the centre than at the edges. It diverges a beam of light on refraction through it. Concave lenses have a virtual focus.

Concave mirror: The type of mirror in which reflecting surface of the spherical mirror is curved inwards, is called concave mirror.

Convex lens: Convex lenses are thicker at the centre and thinner at the edges. It converges a parallel beam of light on refraction through it. It has real focus.

Convex mirror: The type of mirror whose reflecting surface of the spherical mirror is curved outwards, is called convex mirror.

Erect image: When the image formed have same direction as that of object, then the formed image is called erect image.

Magnified image: When the size of image is larger than the object, then it is called magnified image.

Magnifying glass: A magnifying glass is a convex lens that is used to produce a magnified image of an object.

Prism: Prism is a transparent glass pyramid, bounded by four triangular surface that separates white light into a spectrum of colours.

Rainbow: A band of seven colours formed in the sky in the direction opposite to the sun due to rain or presence of water droplets in the atmosphere.

Real image: The image which can be formed or obtained on the screen is known as real image.

Rearview mirror: Rearview mirror is a mirror in automobiles and other vehicles, designed to see a virtual, upright and diminished image of the traffic behind them. For rearview mirror, convex mirror is used.

Side mirror: The rearview mirror is used as side mirror in motor vehicles.

Spherical mirror: ’he mirrors which have curved surfaces are known as spherical mirrors.

Virtual image: The image that cannot be obtained on the screen is known as virtual image.