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This PSEB 7th Class Social Science Notes Chapter 4 Ocean will help you in revision during exams.

PSEB 7th Class Social Science Notes Chapter 4 Ocean

→ Oceans: The big reservoirs of water on earth are known as oceans. The Pacific Ocean, Atlantic Ocean, and Indian ocean are the main oceans.

→ Pacific Ocean: It is the longest and deepest ocean on earth. It is so deep that even the highest peak Mt. Everest can sink in it.

→ Seas: Every ocean is divided into small parts. These small parts are known as seas.

→ Speeds of Ocean Water: The ocean water has three speeds waves, currents, tides.

→ Waves: Ripples in ocean water caused by winds blowing over the sea.

→ Current: When the ocean water starts moving in a specific direction it is known as oceanic current.

→ The speed of oceanic current normally ranges from 2 km/hr to 10 km/hr.

→ Tides: Regular rise and fall of ocean water as a result of the gravitational pull of the sun and the moon. It happens twice in 24 hrs.

→ High tide and Low tide: On a full moon day the tides of the sea rise to the highest level. It is called high tides.

→ When the oceanic tides rise to the lowest level it is called low tides.

→ Water cycle: Unending movement of water between hydrosphere, atmosphere, lithosphere, and back to the hydrosphere.

→ Groundwater: Water that soaks underground, roots of plants help water go underground.

→ Transpiration: Water vapours are returned to the atmosphere by plants.

→ Water budget: The balancing of precipitation on the ground with evaporation and transpiration in the atmosphere.

→ Waves: Ripples in ocean water caused by winds blowing over the sea.

This PSEB 7th Class Social Science Notes Chapter 3 Atmosphere and Temperature will help you in revision during exams.

PSEB 7th Class Social Science Notes Chapter 3 Atmosphere and Temperature

→ Atmosphere: The big protective layer surrounding the earth.

→ Composition of Atmosphere: Atmosphere is a mixture of different gases. Two gases are main Nitrogen (almost 78%) and Oxygen (almost 21%).

→ Layers of Atmosphere: Four layers.

• Troposphere
• Stratosphere
• Mesosphere
• Thermosphere

→ Troposphere: This layer is the closest to the earth. All the happenings take place in the troposphere. This layer protects us from the dangerous ultra-violet rays of the sun.

→ Factors affecting the atmosphere: Three main factors affect the atmosphere

• Latitudes
• Height above the sea level
• Distance from the sea.

→ Global Warming: The increase in global temperatures brought about the increased emission of greenhouse gases into the atmosphere.

→ Troposphere: It is the lowermost layer of the atmosphere.

→ Weather: It is the description of the atmospheric conditions of a particular place at a particular time for a short period of time.

→ Climate: It is the composite or integrated picture of the weather conditions over a long period of time such as a season or a year.

This PSEB 7th Class Social Science Notes Chapter 2 The Internal and External Face of the Earth will help you in revision during exams.

PSEB 7th Class Social Science Notes Chapter 2 The Internal and External Face of the Earth

→ Lithosphere: It includes the earth’s crust called Sial. The normal width of this part is almost 100 kms. It has more Silicon and Aluminium.

→ Minerals: These are those natural substances that are made up of one element or a combination of elements.

→ Rocks: The combined form of natural minerals is called Rocks. These are of three types Igneous, Sedimentary and Metamorphic.

→ Magma: In the depth of the earth, most substances are found in a melt state called Magma.

→ Lava: When magma reaches the earth’s surface, it is called lava.

→ Igneous and Metamorphic Rocks:

• The molten lava cools down, gets solidified, and thus comes into existence-Igneous Rocks.
• Metamorphic rocks come into existence through Igneous and Sedimentary rocks.
• In fact, Igneous and sedimentary rocks undergo a transformation that is chemical as well as structural because of pressure and heat.
• As a result, the construction and structure of these rocks changes, and these are called Metamorphic rocks.
• Example: Granite is an igneous rock while Gneiss made up of Granite is a metamorphosized rock.

→ Metallic and Non-metallic Minerals: Metallic minerals contain metals like iron, silver, etc. while Non-metallic minerals don’t contain metals like Abhrak, Potassium, Gypsum, etc.

→ Preservation of Minerals: It takes hundreds of years the make minerals, so these must be preserved.

→ Crust: The outermost layer of earth.

→ Core: The innermost layer of the earth.

→ Sedimentary rocks: Any rock formed by the deposition of sediments.

→ Mantle: The mantle is the intermediate layer between the crust and the core of the earth.

→ Minerals: A mineral is a naturally occurring substance having a definite chemical composition and physical properties.

→ Lithospheric plates: A large segment of earth crust that can ‘float’ across the heavier, semi-molten rock below.

This PSEB 7th Class Social Science Notes Chapter 1 Environment will help you in revision during exams.

PSEB 7th Class Social Science Notes Chapter 1 Environment

→ Earth: The earth is called a blue planet – 71% is water and 29% is an island.

→ Environment: Environment means surroundings. Its components are the Physical, Biological, and Cultural environment.

→ Physical Environment: The prevailing natural conditions comprising the land, water, and air.

→ Biological Environment: It consists of all life forms – animals including humans, plants, and other organisms.

→ Earth’s Spheres: The above four components form spheres called the lithosphere, hydrosphere, atmosphere, and biosphere.

→ Lithosphere: The outermost layer of the crust is called the lithosphere (Rock-sphere).

→ The rocky layer under continents is called Sial and under oceans is called Sima.

→ Hydrosphere: Rivers, lakes, seas, and oceans comprise this sphere and provide support to all life forms.

→ Atmosphere: The thin layer of air around earth.

→ Biosphere: Biosphere is a narrow zone of contact between land, water, and air. It is a life-giving sphere.

→ Biotic environment: The world of living things.

→ Abiotic environment: The world of non-living things.

→ Components of the environment: Land, Water, Air.

→ Crust: Hardtop layer of the earth.

→ Landforms: Mountains, Plateaus, Plains.

→ Ecosystem: A community of plants and animals within a particular physical environment.

→ Human Environment: Human life is closely related to the environment of the earth.

This PSEB 7th Class Science Notes Chapter 18 Wastewater Story will help you in revision during exams.

PSEB 7th Class Science Notes Chapter 18 Wastewater Story

→ Sewage is liquid waste, most of it is water that has dissolved and suspended impurities. These impurities are called contaminants.

→ An underground network of pipes that carry wastewater from a home to a point of disposal is called Sewerage.

→ Sewage is transported through the closed pipes to the wastewater treatment plants where pollutants are separated and reformed and then flow into rivers and oceans.

→ During wastewater treatment pollutants are separated by physical, chemical, and biological methods.

→ Sludge is a solid that settles to the bottom during water purification.

→ Wastewater treatment co-products are sludge and biogas.

→ A manhole is a lid-covered open space through which a person can enter and can check the sewerage system.

→ Open defecation is a breeding ground for flies, mosquitoes, and other insects that cause many diseases.

→ Do not throw oil, ghee, grease, etc. in a drain or in the open. Doing so will make drain chock.

→ Throw trash only in the bin (dustbin).

→ Pollutants: Dissolved and suspended impurities in dirty water are called pollutants.

→ Sewerage: A network of small and large pipes that carry wastewater to the drainage area.

→ Manhole: Large open mouth holes are made at every 50-60 meters of the sewerage system.

→ Individual who enters the sewage can check and remove sewage problem if any.

→ Water Treatment Plant: A place where impurities are separated from wastewater.

→ Water Treatment: The process of separating impurities from wastewater is called water treatment.

→ Sludge is the solid that settles in the sewage water purification tank.

→ Septic tank: This is a small system of sewage treatment containing monoaerobic bacteria that remove waste products. It has connections with main sewage pipes.

This PSEB 7th Class Science Notes Chapter 17 Forests: Our Lifeline will help you in revision during exams.

PSEB 7th Class Science Notes Chapter 17 Forests: Our Lifeline

→ A system made up of plants, animals, and micro-organisms are called a forest.

→ The top layer of the forest is Canopy Layer, the mid-layer is the Crown layer and the lower layer is the Understory layer.

→ Forests protect the soil from erosion.

→ Soil helps in the growth and development of trees.

→ Humus shows that nutrients from the bodies of dead plants and animals have been incorporated into the soil.

→ Forests act like green lungs and produce many products. That is why forests are so important.

→ A forest is an area whose uppermost layer is topped by trees.

→ Forests are always green.

→ A variety of animals, plants, and insects are found in forests.

→ All wild animals, herbivores or carnivores, depend on plants for food in one or the another way.

→ Forests continue to grow and develop and can regenerate.

→ Forests affect climate, water cycle, and air quality.

→ Trees, shrubs, vegetation, herbs, etc. all are found in forests.

→ According to the height of trees and plants, forests are divided into three categories:

• Canopy
• Crown
• Understory

→ Forest soil helps in regeneration.

→ Forest plants emit vapours and help bring rain and regulate the temperature of the environment.

→ Different layers of vegetation in forests provide food and shelter to animals, birds, and insects.

→ In the forest, soil, water, air, and living things have interdependence on each other.

→ Forests provide important basic necessities for communities living in forested areas.

→ Forests maintain and regulate climate, water cycle, and air quality.

→ Decomposers depend on the dead bodies of plants and animals and turn them into simple substances.

→ Deforestation causes global warming, decreases rainfall, increases pollution, and erodes soil.

→ To maintain balance in nature and maintain habitat for wild animals and plants forest plays an important role.

→ Forest: A forest is an area where there is a lot of dense vegetation, including animals, trees, bushes, and weeds that grow naturally.

→ Canopy: The top layer of tree branches forms a dense top layer of trees on earth which is called the canopy.

→ Crown layer: The layer in which the branches and trunks of trees come, is called the crown or crown layer.

→ Understory Layer: The shaded area below which there is very little light, is called the lower or understory layer.

→ Ecosystems: Living things and their environment work together to create ecosystems. Plants, animals, and microorganisms are the biological components of the ecosystem. These are divided into different categories of producers, consumers, and decomposers.

→ Food chain: In ecology, the sequence of transfer of matter and energy in the form of food from one organism to another organism is called a food chain.
For example:

→ Food Web: A food web consists of a network of many food chains. A food chain helps provide food to organisms at the next food level.

→ Afforestation: The process of planting trees on a large scale is called Afforestation.

→ Decomposers: Microorganisms that decompose the dead bodies of plants and animals into humus, are called Decomposers.

→ Erosion: In the absence of trees and plants top layer of soil is lost, This process of carrying away the topsoil by wind and water is called soil erosion.

→ Replenishment of forest: Planting a large number of plants and trees in the forest area is called forest replenishment.

This PSEB 7th Class Science Notes Chapter 16 Water: A Precious Resource will help you in revision during exams.

PSEB 7th Class Science Notes Chapter 16 Water: A Precious Resource

→ All living things need water to survive.

→ The three states of water are solid, liquid and gas.

→ Less than 1% of the world’s water is freshwater or out of all Earth’s water, only about 0.00367% is available for human consumption.

→ Our future depends on the availability of water.

→ Every year March 22 is celebrated as World Water Day.

→ The minimum recommended amount of water per person is 50 Litres per day.

→ Water scarcity has become a global concern.

→ About 71% of the earth’s surface is covered by water.

→ Almost all the water on the earth is found in the oceans, seas, rivers, land, and atmosphere.

→ Useful water is freshwater.

→ Salt-free water present on Earth is 0.006% of the total amount of water available on Earth.

→ In solid-state water is present as ice and snow found in the snow-covered mountains at the poles of the earth and as glaciers.

→ Water in the liquid state is found in oceans, lakes, rivers as well as groundwater below ground level.

→ In the gas state, water is present in the air in the form of Vapours in the atmosphere.

→ Rainwater is considered to be the purest form of water.

→ The transfer of water is done by the water cycle.

→ The main source of water is groundwater.

→ Groundwater accumulates in the layers of stable hard rocks.

→ Population growth, increase in industrial and agricultural activities, etc. affect the groundwater level.

→ Groundwater level decreases due to high utilization of groundwater and low absorption of water by land.

→ Rainwater is used for rainwater harvesting.

→ Factors affecting groundwater levels are deforestation and excessive water absorption.

→ Bawris and Drip irrigation systems are some of the techniques that can be used to meet water scarcity.

→ Without water, greenery will disappear from the earth, which means the end of life.

→ Time demands that everyone should use water sparingly. Hence the unwanted and excessive use of groundwater should be avoided.

→ When plants are not watered for a few days, they wither away and eventually die.

→ The Punjab Government had passed the Water Conservation Act 2009 of Punjab in the year 2009 under which the date of transplantation of Paddy crop for the first time was fixed on 10th June. This was later changed to June 15, 2015.

→ The Dead Sea is a salty lake bounded on the east by Jordan and on the west by Israel and Palestine.

→ It is 8.6 times saltier than the other oceans having more alkalinity, the cause non-existence of plants and living creatures, which is why it is called the Dead Sea.

→ Water Cycle: Many processes such as evaporation of water into the air, formation of clouds through condensation, and the occurrence of precipitation which maintains water on the earth, even though the whole world uses it is called the water cycle.

→ Fresh Water: The water that is suitable for drinking is freshwater. It contains a very small amount of salt. This is about 3% of the total water on earth, which is found in rivers, lakes, glaciers, snow-capped peaks, and underground.

→ Water table: At a depth near the water source where the space between the rocks is filled with water is called groundwater area or saturated area. The surface of this water is called the water table.

→ Wet Rock layer: Groundwater between layers of hard rock below the water table is called the wet rock layer. This water is drained through tube wells.

→ Infiltration: Water from various sources such as rain, rivers, and ponds is going even deep inside the earth due to gravity. This is called infiltration.

→ Water management: The efficient distribution of water is called water management.

→ Drip Irrigation System: This is an irrigation technique in which water is dripped through pipes to the plant.

→ Water Storage: The process of collecting rainwater and using it when needed is called water storage. This is done to compensate for the water level.

→ Bawris: This is the ancient method of water storage. This method is still practiced in many parts of India today.

This PSEB 7th Class Science Notes Chapter 15 Light will help you in revision during exams.

PSEB 7th Class Science Notes Chapter 15 Light

→ A ray coming from a source of light falls on the object and after reflection enters our eyes so that we see the objects.

→ Light always travels in a straight line.

→ The reflection from the surface of the object must be the same to see the image.

→ After hitting a surface, the light returns to the same medium in a certain direction. The process of coming back of the light is called reflection of light.

→ The ray of light that strikes an object is called an incidental ray and the ray of light which after hitting an object returns to the same medium in a particular direction it is called a reflected ray.

→ The angle between the incident ray and the perpendicular drawn at the point of incidence is called the Angle of Incidence.

→ The angle between the reflected ray and the perpendicular drawn at the point of reflection is called the angle of reflection.

→ The angle of incidence and the angle of reflection are always equal. This is called the law of reflection.

→ The image formed on the screen is called a Real image.

→ The image that cannot be obtained on the screen even if the reflected rays appear to meet is called a Virtual image.

→ The image formed by a plane mirror is always formed behind the mirror. This image is virtual is erect and of the same size as that of the object.

→ The image formed by a plane mirror is at the same distance behind the mirror as the object is placed in front of the mirror.

→ The image formed by a plane mirror is laterally inverted i.e. the left side of the object becomes to the right of the image and the right side of the object is seen to be left of the image.

→ A concave mirror is a spherical mirror with a reflecting surface facing inwards.

→ A convex mirror is a spherical mirror with a reflecting surface facing outwards.

→ The rays of light coming from a distant object are considered to be parallel to each other and the point at which they actually meet after being reflected from the mirror or appear to meet is called the focal point of the mirror.

→ For a concave mirror, a virtual, erect, and large image is formed only when the object is placed between the principal focus and the mirror.

→ For a convex mirror, the image formed is erect, virtual, and smaller in size than the size of the object.

→ The lens is a piece of transparent medium surrounded by two surfaces. The two main types of lenses are

• Convex lens
• Concave lens

→ The convex lens is thicker in the middle and thinner at the edges.

→ The concave lens is thin in the middle than at the edges.

→ A convex lens is also called a Convergent lens whereas a Concave lens is called a Divergent lens.

→ The convex lens can be used to see small objects. Hence it is also called magnifying glass or reading glass.

→ On allowing white light to pass through a prism, it splits up into seven colours, which means white light is composed of seven colours.

→ The point at which the rays of light coming from a distant object (such as the sun) meet or appear to meet after suffering refraction from the lens is called the focal point of the lens.

→ When a ray of light enters from one medium to another transparent medium, it changes its path. The phenomenon of light changing its path is called the refraction of light.

→ Reflection of light: When light travelling in a straight line strikes the surface of a mirror or a polished opaque surface, it changes its direction and returns to the same medium. The process of coming back from the light is called the reflection of light.

→ Incidental ray: A ray of light falling on the smooth and polished surface is called an incident ray.

→ Reflected Ray: A ray of light after striking a mirror changes its direction and returns to the same medium, which is called a reflected ray.

→ The angle of incidence: The angle between the incident ray and the perpendicular drawn at the point of incidence is called the angle of incidence.

→ The angle of reflection: The angle formed between the reflected ray and the perpendicular drew at the point of incidence is called the angle of reflection.

→ Point of incidence: The point at which the incident ray strikes the surface of the mirror, is called the point of incidence.

→ Perpendicular: The normal or perpendicular line drawn from point of incidence.

→ Real Image: When the light coming from an object after reflection meets at a point forming an image then such image is called a real image.

→ Virtual reflection: When the rays of light only appear to meet at a point after reflection from a mirror then that point is called a virtual image. A virtual image cannot be obtained on the screen.

→ Spherical Mirror: A mirror whose reflecting surface is a part of a hollow spherical surface.

→ Concave mirror: If the inner surface of a spherical mirror is reflecting, it is called a concave mirror.

→ Convex mirror: If the outer surface of the spherical mirror is reflecting, it is called a convex mirror.

→ Light Reflection: The bouncing back of light after when light strikes a smooth surface.

→ Refraction of Light: When a ray of light enters from one transparent medium to another transparent medium, the ray of light changes its path. The phenomenon of change of path by light is called refraction.

→ Convex lens: This is a piece of transparent shell that is thicker in the middle than the edges. It is also called a converging lens.

→ Concave lens: This is a piece of the transparent medium that is thin in the middle and thick at the edges. This lens is also called a diverging lens.

→ Focus: The point on the principal axis where the parallel rays of light meet or appear to meet after passing through the lens is called the focus.

→ Focal length: The distance between the principal focus and the center of the lens is called the focal length of the lens.

→ Splitting of light: The process of splitting by when white light passes through a transparent medium (such as a prism of glass) of white light into seven colours is called the splitting of light.

→ Spectrum: It is a band of seven colours obtained after passing white light through the prism. These colors from top to bottom are Violet, Indigo, Blue, Green, Yellow, Orange, and Red.