Important Question Answers for the Class 9-Social Science Chapter 3- Atmosphere and Climate
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The Big Questions:
1. What is the composition of the atmosphere?
The atmosphere contains 78% nitrogen and 21% oxygen.
It also contains argon, carbon dioxide and other gases in small amounts.
Water vapour and dust particles help in cloud formation and rainfall.
2. How do the different layers of the atmosphere affect the Earth?
Troposphere: It contains air and produces weather conditions.
Stratosphere: Its ozone layer blocks harmful solar radiation.
Mesosphere: It burns up most meteorites entering the atmosphere.
Thermosphere: It supports radio communication and produces auroras.
Exosphere: Light gases escape into space from this layer.
3. What is the mechanism of monsoon?
Monsoons are seasonal winds caused by unequal heating of land and sea.
In summer, low pressure develops over land and high pressure over the ocean.
Moist south-west winds blow towards land and bring rainfall.
In winter, high pressure develops over land and winds blow towards the sea.
These winds collect moisture from the Bay of Bengal and rain on India’s eastern coast.
4. How can we reduce our carbon footprint?
Save electricity and use renewable energy.
Walk, cycle or use public transport.
Plant trees, recycle waste and avoid single-use plastics.
Chapter 3: Atmosphere and Climate
1. What is atmosphere? Explain its composition with the help of a pie diagram.
The atmosphere is the blanket of air surrounding the Earth. It is held around the Earth by gravity.
Composition:
Nitrogen – 78%
Oxygen – 21%
Argon – 0.93%
Carbon dioxide – 0.04%
Other gases – 0.03%
It also contains water vapour and dust particles.
Draw a pie chart using the percentages given above.
2. Draw a labelled diagram of the structure of the atmosphere.
Draw and label the layers in the following order:
Troposphere: Surface to about 12 km
Stratosphere: Up to 50 km
Mesosphere: Up to 80 km
Thermosphere: From 80 to 700 km
Exosphere: Above 700 km
Also mark the tropopause, stratopause, mesopause and ozone layer.
3. Which are the four main seasons of India?
The four main seasons recognised by the IMD are:
Winter season: December to early April
Summer or pre-monsoon season: April to June
Monsoon or rainy season: June to September
Post-monsoon or retreating monsoon season: October to December
4. Why do you not feel the pressure of the atmosphere?
Air presses upon our bodies from all directions.
Our bodies exert an equal pressure in the opposite direction.
Therefore, the two pressures balance each other.
5. In which layer of the atmosphere do aeroplanes fly and why?
Aeroplanes usually fly in the stratosphere because:
It is mostly free from clouds.
It has fewer weather disturbances.
The air is stable, making flights smoother.
6(a). Distinguish between the troposphere and stratosphere.
| Troposphere | Stratosphere |
|---|---|
| It is the lowest atmospheric layer. | It lies above the troposphere. |
| It extends to about 12 km. | It extends up to 50 km. |
| Most weather changes occur here. | It is mostly free from weather disturbances. |
| It contains clouds and water vapour. | It contains the protective ozone layer. |
6(b). Distinguish between the south-west and north-east monsoon.
| South-West Monsoon | North-East Monsoon |
|---|---|
| It occurs mainly from June to September. | It occurs mainly from October to February. |
| Winds blow from sea towards land. | Winds generally blow from land towards sea. |
| It brings rainfall to most parts of India. | It mainly rains along the south-eastern coast. |
| It is also called the summer monsoon. | It is also called the winter monsoon. |
7. Study of Temperature and Rainfall Data
7.1 Arrange the stations according to their distance from the equator.
From nearest to farthest:
Thiruvananthapuram
Bengaluru
Chennai
Mumbai
Nagpur
Kolkata
Shillong
Jodhpur
Delhi
Leh
7.2 Find out:
(a) Two stations with the most extreme climate:
Leh
Jodhpur
(b) Two stations influenced by the retreating monsoon:
Chennai
Thiruvananthapuram
(c) Two hottest stations:
February: Thiruvananthapuram and Chennai
June: Jodhpur and Delhi
7.3 Answer the following:
(a) Why does Shillong receive more rainfall than Kolkata?
Shillong lies on the windward side of the Meghalaya hills.
Moist winds rise along the hills and cause heavy rainfall.
Kolkata lies in the plains and receives comparatively less rainfall.
(b) Why does Delhi receive more rainfall than Jodhpur?
Monsoon winds reaching Delhi contain more moisture.
Jodhpur lies in a dry region away from the sea.
The Aravalli Range runs parallel to the monsoon winds and does not cause much rainfall.
7.4 Answer the following:
(a) Why does Thiruvananthapuram have an equable climate?
It is located near the sea.
The sea moderates its temperature.
Therefore, it has neither very hot summers nor very cold winters.
(b) Why does Chennai receive more rainfall after the main monsoon is over?
Chennai receives most of its rain from the north-east monsoon.
These winds collect moisture from the Bay of Bengal.
They bring heavy rainfall during October and November.
(c) Why does Leh receive light precipitation throughout the year?
Leh lies in the rain-shadow region of the Himalayas.
The mountains block moisture-bearing monsoon winds.
Western disturbances bring some precipitation during winter.
7.5 How do monsoons provide climatic unity to India?
Most parts of India receive rainfall from monsoon winds.
Agriculture across the country depends heavily on monsoon rainfall.
Monsoons affect rivers, reservoirs, crops and water supply.
They influence people’s occupations, festivals and daily lives.
Thus, monsoons unite India under a common seasonal cycle.
8. Relationship between houses, clothing and climatic conditions
| Region | Houses | Clothing |
|---|---|---|
| Himalayan region | Sloping roofs made of wood or stone | Thick woollen clothes |
| Rajasthan | Thick walls and flat roofs | Loose, light-coloured cotton clothes |
| Assam | Houses on stilts with sloping roofs | Light cotton clothes and rain protection |
| Coastal areas | Sloping tiled roofs with ventilation | Light cotton clothes |
Thus, the houses and clothing of people are adapted to the climate and relief of their regions.
Very Short Answer Type Questions:
1. Which layer of the atmosphere contains the ozone layer?
Answer:
The stratosphere contains the ozone layer.
2. Name the gas that makes up the highest percentage of the atmosphere.
Answer:
Nitrogen makes up the highest percentage of the atmosphere.
3. Which element of weather is measured using a barometer?
Answer:
A barometer is used to measure atmospheric pressure.
4. What is the normal duration of the southwest monsoon in India?
Answer:
The southwest monsoon usually lasts from June to September.
5. Which season in India is known as the “hot weather season”?
Answer:
The summer season is known as the hot weather season.
6. Name the process by which water vapour turns into clouds.
Answer:
The process is called condensation.
7. What term is used for long-term average weather conditions of a place?
Answer:
It is called climate.
8. Which greenhouse gas is mainly released by burning fossil fuels?
Answer:
Carbon dioxide is mainly released by burning fossil fuels.
9. What is the immediate cause of floods in most regions?
Answer:
The immediate cause of floods in most regions is heavy rainfall.
10. What does the term “carbon footprint” refer to?
Answer:
Carbon footprint refers to the total amount of greenhouse gases, mainly carbon dioxide, released due to human activities.
Short Answer Type Questions:
1. State any two differences between weather and climate.
Answer:
- Weather refers to day-to-day atmospheric conditions, while climate refers to long-term average weather conditions.
- Weather changes quickly, but climate changes over a long period.
- Weather includes daily temperature, rainfall, wind and humidity; climate shows the general pattern of these elements in a region.
2. Why is the troposphere important for human life?
Answer:
- The troposphere contains most of the atmospheric mass and essential gases.
- All weather phenomena such as clouds, rain, storms and fog occur in this layer.
- It supports life and plays an important role in controlling climate.
3. Explain the role of nitrogen in the atmosphere.
Answer:
- Nitrogen is the largest component of the atmosphere.
- It does not directly support respiration or burning, but it reduces the intensity of oxygen and prevents rapid combustion.
- Nitrogen is also important for plant growth through the nitrogen cycle.
4. How does altitude affect temperature?
Answer:
- Temperature decreases as altitude increases.
- At higher altitudes, air pressure and air density become lower.
- This is why hill stations and mountain regions remain cooler than plains.
5. Mention two characteristics of the retreating monsoon season in India.
Answer:
- The retreating monsoon season occurs mainly during October and November.
- The southwest monsoon starts withdrawing from India during this period.
- Tamil Nadu and the Coromandel Coast receive rainfall from retreating monsoon winds and cyclones.
6. Why do coastal areas experience moderate climate?
Answer:
- The sea heats up and cools down slowly.
- Therefore, coastal areas do not become extremely hot in summer or extremely cold in winter.
- The sea acts as a temperature moderator and reduces temperature differences.
7. Give two human activities responsible for climate change.
Answer:
- Burning fossil fuels such as coal, petrol and natural gas.
- Deforestation, which reduces the number of trees that absorb carbon dioxide.
- Industrial activities and excessive consumption also increase greenhouse gases.
8. Explain how deforestation contributes to floods.
Answer:
- Trees help absorb rainwater and hold soil together.
- When forests are cut, rainwater flows quickly over the land and causes soil erosion.
- This increases runoff and may lead to floods in low-lying areas.
9. State two impacts of global warming on India’s climate.
Answer:
- Global warming increases average temperatures, leading to hotter days and heatwaves.
- It can increase extreme weather events such as floods, droughts and storms.
- Melting glaciers can also increase the risk of glacial lake outburst floods.
10. Suggest two ways by which individuals can reduce the amount of carbon footprint.
Answer:
- Use public transport, cycling or walking instead of private vehicles.
- Save electricity and use energy-efficient appliances.
- Plant more trees and follow reduce, reuse and recycle practices.
Long Answer Type Questions:
Answer:
Troposphere
- It is the lowest layer of the atmosphere.
- Most weather activities such as rain, clouds, storms and fog occur here.
- It contains water vapour and greenhouse gases that help regulate temperature.
- It lies above the troposphere.
- It contains the ozone layer, which absorbs harmful ultraviolet rays from the Sun.
- This protects humans, animals, plants and marine life.
- It lies above the stratosphere.
- Meteors burn up in this layer before reaching the Earth.
- It helps protect the Earth from falling space particles.
- This layer has very high temperatures.
- It helps in radio communication because it reflects radio waves.
- It also supports satellite communication.
- It is the outermost layer of the atmosphere.
- Many satellites move in this region.
- It gradually merges with outer space.
2. Explain the elements of weather and analyze how they collectively influence the climate of a region.
Answer:
Temperature:
- It tells how hot or cold the atmosphere is.
- It is measured using a thermometer.
- Temperature affects wind, rainfall and daily life.
- It is the weight of air pressing on the Earth’s surface.
- It is measured by a barometer.
- Low-pressure areas may lead to storms or cyclones.
- Wind is moving air.
- It moves from high-pressure areas to low-pressure areas.
- Wind affects temperature, humidity and rainfall.
- Humidity is the amount of water vapour in the air.
- High humidity makes the air feel sticky and slows evaporation.
- It affects rainfall and comfort.
- It includes rain, snow, sleet and hail.
- Rainfall is measured using a rain gauge.
- It affects agriculture, water supply and vegetation.
Answer:
1. Hot Weather Season / Summer- It occurs from March to May.
- Temperatures rise sharply in many parts of India.
- Hot and dry winds called loo blow in northern and northwestern India.
- It occurs from mid-November to February.
- Northern India experiences cold conditions.
- The southern parts remain comparatively warm.
- It starts around the first week of June.
- Moisture-laden southwest monsoon winds bring heavy rainfall.
- Most parts of India receive rainfall during this season.
- It occurs mainly in October and November.
- The southwest monsoon withdraws from India.
- The Tamil Nadu coast receives rainfall from the retreating monsoon.
Answer:
Arabian Sea Branch:
- It brings heavy rainfall to the western coast and Western Ghats.
- Areas on the leeward side, like parts of the Deccan Plateau, receive less rainfall.
- It brings rainfall to northeastern India, the Ganga plains and other regions.
- It is responsible for heavy rainfall in places like Meghalaya.
Importance of southwest monsoon:
- It provides most of India’s annual rainfall.
- It supports agriculture and crop production.
- It fills rivers, lakes, reservoirs and groundwater sources.
- It affects the economy, food prices and rural employment.
- It influences Indian culture, festivals and daily life.
Answer:
- Indian agriculture depends greatly on monsoon rainfall. Crops like rice, pulses, cotton and sugarcane need timely rain.
- Rivers, ponds, lakes and reservoirs are filled during the monsoon. This water is used for drinking, irrigation and industries.
- If monsoon rainfall is poor, crops fail, food prices rise and farmers suffer. This condition is called monsoon failure.
- Good monsoon rainfall improves crop production and supports rural livelihoods.
- Many festivals, songs and traditions in India are connected with rain and farming.
Answer:
Burning fossil fuels
- Coal, petrol and natural gas release greenhouse gases such as carbon dioxide.
- Cutting forests reduces the number of trees that absorb carbon dioxide.
- Factories and farming release harmful gases like methane and nitrous oxide.
- Excessive use of energy and goods increases emissions.
- Rising global temperatures.
- Melting glaciers and polar ice.
- Rise in sea level.
- More frequent floods, droughts, storms and wildfires.
- Loss of biodiversity and damage to ecosystems.
- Food and water shortages.
Answer:
- Heavy rainfall during monsoon.
- Overflowing rivers and reservoirs.
- Cyclones and storm surges in coastal areas.
- Melting glaciers and glacial lake outburst floods.
- Poor drainage systems in cities.
- Construction on floodplains and blocked waterways.
- Rivers, floodplains and drainage basins should be mapped properly.
- Construction should be avoided in flood-prone areas.
- Early warning systems help people move to safer places.
- Drainage systems should be improved to carry floodwater quickly.
- These structures help divert or control floodwater.
- Important buildings and houses can be built on raised platforms.
Answer:
- Burning fossil fuels like coal, petrol and natural gas.
- Transport such as cars, buses and airplanes.
- Electricity generation in thermal power plants.
- Industries and factories.
- Deforestation.
- Use of household appliances such as air conditioners and refrigerators.
- Agriculture and livestock farming.
Answer:
Individual Level- Use public transport, cycling or walking.
- Save electricity and use energy-efficient appliances.
- Reduce, reuse and recycle materials.
- Plant more trees.
- Avoid unnecessary consumption.
- Promote renewable energy such as solar and wind power.
- Protect forests and encourage afforestation.
- Improve public transport systems.
- Control industrial pollution.
- Prepare disaster management plans.
- Countries should cooperate to reduce greenhouse gas emissions.
- International agreements should support climate action.
- Rich and developed countries should help poorer countries with technology and funds.
- Global awareness and sustainable development should be promoted.
The atmosphere is a thick blanket of gases surrounding the Earth. It protects life, controls weather and climate, and maintains the Earth’s temperature.
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