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Chapter: 5th Social Science : Term 1 Unit 4 : Atmosphere


5th Social Science : Term 1 Unit 4 : Atmosphere : Text Book Back Exercises Questions with Answers, Solution, Evaluation

Unit 4


Ravi : Where do we get the most significant thing that we need?

Devi : From the Biosphere of our earth.

Ravi : What is Biosphere?

Devi : Biosphere is the combination of lithosphere, hydrosphere and atmosphere.

Ravi : What is atmosphere? Shall we study about it?


Do you Know?

Lithosphere – Land on Earth

Hydrosphere – Water on Earth

Atmosphere – Air on Earth

Biosphere – Life on Earth



Atmosphere is the envelope of air around the Earth.



Weather is a day to day conditions of atmosphere at any place in regard to temperature, pressure, wind, humidity, and rainfall.

* Is there any poet who does not love the nature?

* Is there any human who does not enjoy air?

The word ‘weather’ is often used by us in our day to day life

World Weather Day March – 23



Climate is the average weather for a given period of time.

The world climate is derived from the Greek word called ‘clima’


Try this

Take a ball and throw it up in the air observe the increasing speed of the ball when it comes down.


Do you know?

We know that the gravitational force increases near the Earth and decreases as we go higher.

As a result the density of air also differs and can be found in five layers called Troposphere, Stratosphere, Mesosphere, Thermosphere and Exosphere.

All the major changes occur in the Troposphere. The study of weather is called Meteorology.


Solar radiation:

The Earth receives heat energy from the Sun in the form of radiation. It is called solar radiation.

World Environment Day, June-5

World Ozone Day, September-16

 Farenheit, Celsius, Kelvin are the units to measure temperature


The sun is the only source of light to all the planets in the solar system. The land, water and air in our planets receives heat from the sun.



Write the significance of gases

Oxygen : For living things to exist

Carbon di oxide : For plants to prepare food by photo synthesis.

Ozone : To protect the earth from UV radiation of the sun.


Efects of solar radiation

* Land – Conduction

* Water – Convection

* Atmosphere - Terrestrial radiation

The earth has the capacity to reflect the rays from the sun.

The temperature is not same everywhere. Latitude, altitude, distance from the sea, position of the mountains are some of the factors that determine the temperature of a place.


Find out how it differs

Signi­ficance of Latitude and Longitude

­* Latitude and Longitude together make grid.­

* Thus grid helps us to locate a place correctly.



Latitude / parallels

The imaginary lines drawn horizontally on the Earth surface from west to east are called latitudes. There are 180 latitudes or parallel circles drawn around the earth surface both in Northern and Southern hemispheres respectively.

Some important latitude are

(1) Equator - 0°

(2) Tropic of cancer -23 ½° North

(3) Tropic of Capricorn-23 ½° South

(4) Arctic Circle - 66 ½° North

(5) Antarctic Circle - 66 ½° South

(6) North Pole and South Pole end at a point of – 90° North and 90° South

(7) Equators is the great circle at the centre of the earth

Longitude / Meridians

(1) These are the semi circles extended from North Pole to South Pole.

(2) The 0° longitude is called prime meridian. It passes through a place called Greenwich in London, England.

(3) The earth rotates on its axis once in 24 hours. There are 360 longitudes on the Earth. Sunlight takes 4 minutes time to move 1°.

(4) 82.30° East longitude is the Indian Standard Time (IST) that passes through Allahabad in India.

(5) It is 5.30 hours ahead of Greenwich Mean Time (GMT).

(6) 82.30° × 4’ = ____________?



In which latitude and longitude is your school located?

Heat Zones of the Earth


Do you Know ?

Why does the heat vary from morning to evening?

It is because of the sun’s rays.

The land is divided into various heat zones according to the fall of sun’s rays on the surface of the Earth.

The zone between Tropic of Cancer and Tropic of Capricorn is called Tropical or Torrid zone, where the sun’s rays fall vertically.

The zone between 23½° N to 66½° N latitude and 23½° S to 66½° S latitude which receive slanting rays of the sun are called Temperate zone. The zones which do not Get Sun’s rays are called Frigid zones.



The highest mountain in the world is Himalayas.

Apart from the famous mountain peaks like Mount Everest, K2,Kanchenjunga there are other peaks like Nanga Parbat, Annapurna, Dhaulagiri. Mount Everest is the highest peak in the world. It rises to a height of 8,848m above sea level.

Do you Know?



Doddabetta is the highest peak in the Nilgiri ranges. It rises to a height of 2,637 metres. There is a reserved forest area around the peak. It is 9 km from Ooty, on the Ooty-Kotagiri Road in the Nilgiris district of Tamil Nadu, India.



When the temperature increases, pressure decreases and when the temperature decreases, pressure increases

Barometer used for measuring the pressure.

The average pressure of ocean is 1013 mlb.



The air which moves horizontally from high pressure to low pressure area is called wind.


How do you find the direction and speed of the wind?

Devi: The national flag which was hoisted in the morning is flying from West to East.

Ravi: My toy fan was swirling very fast when I showed it outside.

Air never moves in one direction.It differs from place to place and time to time. This is due to the rotation of the earth.


Do you Know?

The instrument used to measure the direction of wind is wind vane.

The instrument used to measure the speed of the wind is Anemometer.


Wind Energy

Wind energy is a form of renewable energy. Wind turbines converts the kinetic energy into mechanical energy. A generator can convert mechanical energy into electricity.


Do you Know?

Loo Wind

The ‘Loo’ is a strong, dusty, gusty, hot and dry summer wind from the west which blows over of North Western India. It is especially strong in the months of May and June. Due to it very high temperature, exposure to it often leads to fatal heatstrokes.


Different types of wind

Planetary wind:

These winds move in the same direction throughout the year with the rotation of the Earth.

Monsoon winds:

The word monsoon is derived from the Arabic term ‘mausim’ which means season.


* South West monsoon winds

 * North East monsoon winds


Sea breeze:

It blows from sea to land during the evening.


Land Breeze:

It blows from land to sea in the morning


Local wind:

It affects the weather.

* Warm local wind – North West India

* Cool local wind – North East India


Jet streams

Air currents in the upper layers of atmosphere is known as Jet streams.

It could determine the arrival and departure of monsoon winds in India.


Hurricane / cyclone

Hurricane changes its position and direction with time to time.

The speed of winds also changes with time. It gives very heavy rainfall.


Types of clouds

The clouds are composed of water vapour in the air. The clouds are divided into four categories on the basis of appearance and height. They are

1. Cirrus cloud

2. Stratus cloud

3. Cumulus cloud

4. Nimbus cloud


1. Cirrus cloud

These clouds appears like a silver grey fish at a very high altitude in the sky. These may not give rain.

2. Stratus cloud

They are grey in colour and are spreadout. They may give small shower.

3. Cumulus cloud

It looks like a burst cotton and gives convectional rain fall.

These clouds are associated with rainfall lightning and thunder.

4. Nimbus cloud

It appears as dark or grey in color. It gives heavy rainfall. It is called vertical or rain clouds.


Look at the sky: write

How does the cloud appear today?__________________________

What would be the consequences ?__________________________


Rain fall

Condensation of the wind causes rain fall

Rain water must be saved and not be wasted.


Convectional Rain fall

During summer solar insolation takes place in land. Water evaporates from lakes, ponds and vegetations. Due to this a heavy rainfall with lightning and thunder occurs in the evening for a short period.



Natural Environment

The natural materials and living things, including sunlight are called environment.


Rain water harvesting

Rain water harvesting is a technique of collection and storage of rainwater into natural reservoirs or tanks, or the infiltration of surface water into subsurface aquifers (before it is lost as surface runoff ).One method of rainwater harvesting is rooftop harvesting.

Orographic Rain fall

When the moisture laden winds from the sea climb the hill slopes, it becomes cool and cause heavy rainfall. The opposite side of the mountain is called Leeward side. It receives very little rainfall.

Cyclonic rainfall

The warm air from the hot area is heated and moves upwards. Hence a low pressure area is developed and it attracts air from high pressure area. Owing to Earth’s rotation a circular motion of winds develop.It gets cooled and brings heavy rainfall.


Do you Know?

Thunder- Lightning

How do we know that the thunder is going to hit?

When the clouds of positive and negative (+,−) charge hit each other, lightning and thunder are produced. Light travels faster than sound, therefore thunder follows lightning. When all the characteristics together activate at the same time it is called weather factory.

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