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NCERT Class 7 Social Science Chapter 24 Air
Also, you can read the NCERT book online in these sections Solutions by Expert Teachers as per Central Board of Secondary Education (CBSE) Book guidelines. CBSE Class 7 Social Science Solutions are part of All Subject Solutions. Here we have given NCERT Class 7 Social Science Chapter 24 Air and After, NCERT Class 7 Social Science Textbook of Our Pasts – II: History, Social and Political Life – II: Civics, Our Environment: Geography. for All Chapters, You can practice these here.
Our Environment [Geography]
QUESTIONS WITH ANSWERS
I. Answer the following questions:
Q.1. What is atmosphere?
Ans: Blanket of air or gases surrounding the earth is called an atmosphere.
Q.2. Which two gases make the bulk of atmosphere?
Ans: Nitrogen and Oxygen make the bulk of atmosphere.
Q.3. Which gas creates green house effect in the atmosphere?
Ans: Carbon dioxide (CO2).
Q.4. What is weather?
Ans: Condition of atmosphere recorded over a small area for a short period of time is called weather.
Q.5. Name three types of rainfall.
Ans: Convectional rainfall, Orographic rainfall and Cyclonic rainfall.
Relief (Orographic) Rainfall
Q.6. What is air pressure?
Ans: The pressure exerted by the weight of air on the earth’s surface is known as air pressure.
II. Tick the correct answer:
Q.1. Which of the following gases protects us from harmful sun rays?
(a) Carbon dioxide.
Ans: (c) Ozone.
Q.2. The most important layer of the atmosphere is ________.
Ans: (b) Troposphere.
Q.3. Which of the following layer of the atmosphere is free from clouds?
Ans: (b) Stratosphere.
Q.4. As we go up the layers of the atmosphere, the pressure
(c) Remains the same.
Ans: (b) Decreases.
Q.5. When precipitation comes down the earth in the liquid form, it is called _______.
Ans: (b) Rain.
III. Match the following:
|(i) Trade winds||(a) Seasonal wind|
|(ii) Loo||(b) Horizontal movement of air|
|(iii) Monsoon||(c) Permanent winds|
|(iv) Wind||(d) Local wind|
|(i) Trades||(c) Permanent winds|
|(ii) Loo||(d) Local wind|
|(iii) Monsoon||(a) Seasonal wind|
|(iv) Wind||(d) Horizontal movement of air|
IV. Give reasons:
1. Wet clothes take longer time to dry on a humid day.
Ans: Because on a humid day air is full of water vapour, hence evaporation is very slow. This is the reason why wet clothes take longer time to dry.
2. Amount of insolation decreases from equator towards poles.
Ans: Insolation comes through vertical rays on equator and covers up less space, but feel more heat there. When it goes up from equator towards poles, the sun rays become slanting. These slanting rays take up more space, the degree of hotness is felt less. Hence amount of insolation decreases towards the poles.
V. For Fun:
1. Solve the crossword puzzle with the help of the clues.
Q.2. Make a weather calendar for one week. Use picture or symbols to show different types of weather. You can use more than one symbol in a day if the weather changes. For example, the sun comes out when rain stops. An example is given below
SOME OTHER IMPORTANT QUESTIONS FOR EXAMINATION
Very Short Answer Type Questions
Q.1. What is the meaning of term atmosphere?
Ans: The term atmosphere is a compound word, of ‘atmos’ meaning air and ‘sphere’ denoting the realm of the earth. The history of this layer of earth is closely linked to the oceans.
Q.2. Name the main gases present in the atmosphere.
Ans: Nitrogen, oxygen, carbon dioxide, helium, ozone, argon and hydrogen.
Q.3. Which is the second most plentiful gas in the air?
Ans: Oxygen is the second most plentiful gas in the air.
Q.4. Into how many layers starting from the earth’s surface is our atmosphere is divided?
Ans: Our atmosphere is divided into five layers starting from the earth’s surface.
Q.5. Name the different layers of atmosphere.
Ans: The different layers of atmosphere are Troposphere, Stratosphere, Mesosphere, Thermosphere and Exosphere.
Q.6. Which is the most important layer of the atmosphere?
Ans: Troposphere is the most important layer of the atmosphere.
Q.7. Name the most plentiful gas in the air.
Ans: Nitrogen is the most plentiful gas in the air.
Q.8. What is the standard unit of measuring temperature?
Ans: The standard unit of measuring temperature is degree celsius. It was invented by Anders Celsius.
Q.9. What is mesopause?
Ans: The zone between mesosphere and thermosphere, from where the temperature starts increasing is called mesopause.
Q.10. What is stratosphere?
Ans: The layer above the troposphere extending from 8 km to 50 km is called stratosphere.
Q.11. What is weather?
Ans: Weather is a state of atmosphere at a given place or an area, over a short period of time.
Q.12. What do you mean by climate of a place?
Ans: Climate of a place is the average weather condition prevailing in a place over a long sir period of time.
Q.13. Name the elements of weather and climate that determine and influence them.
Ans: Temperature, atmospheric pressure and winds are three interrelated and common elements of weather and climate that determine and influence them in the short run and long run respectively.
Q.14. What is wind?
Ans: The horizontal movement of air along the earth’s surface is called wind.
Q.15. What are Planetary Winds or Permanent Winds?
Ans: The winds blowing in the same direction throughout the year are known as Planetary Winds or Permanent Winds.
Q.16. What is a cyclone?
Ans: A cyclone is a wind system where low pressure centre is surrounded by a high pressure centre.
Q.17. Which winds are called local winds?
Ans: There are certain winds in different parts of the world that blow over small areas for short periods. Such winds are called local winds.
Short Answer Type Questions
Q.1. Name the different layers of atmosphere.
Ans: The five major layers of atmosphere are:
Q.2. What is thermosphere? Write a brief note on it.
Ans: The layer above the mesopause is known as thermosphere. It is the zone of high temperature. The lower portion of the thermosphere between 100-400 km is known as Ionosphere because it contains electrically-charged particles called ions. These ions reflect radio waves back to the earth, which help in long distance communication. The temperature in this layer reaches up to 1480°C.
Q.3. What do you know about solar radiation and insolation?
Ans: The sun radiates heat in all directions. This heat is known as solar radiation. The earth receives only 1 out of 2 billion parts of heat radiated by the sun due to its distance from the sun.
The solar radiation that reaches the surface of the earth is known as insolation, it goes on decreasing horizontally from the equator to the poles and varies from place-to-place on Earth.
Q.4. Explain in brief about different types of scales used for measuring temperature.
Ans: There are different types of scales for measuring temperature. These are Celsius, Fahrenheit and Kelvin. In India, the celsius or decimal scale is used. On this scale, temperature is measured in degree celsius. In the celsius thermometer, the freezing point of water is 0°C while the boiling point of water is 100°C.
Q.5. Write the importance of atmospheric pressure.
Ans: Importance of Atmospheric Pressure:
1. Difference in the atmospheric pressure gives rise to the wind systems on the earth.
2. Changes in the atmospheric pressure influence the weather.
3. Weather of an area can be forecast by studying the change in the air pressure.
Q.6. What is humidity? How will you differentiate between absolute humidity and relative humidity?
Ans: The amount of water vapour or moisture present in the atmosphere is called humidity. Humidity varies from place-to-place and time-to-time. There are two types of humidity-absolute humidity and relative humidity.
Difference between absolute humidity and relative humidity:
The amount of water vapour in atmosphere is called absolute humidity, whereas the percentage of water vapour is known as relative humidity.
Q.7. Name and explain different types of winds.
Ans: Different types of winds are Permanent winds, Seasonal winds and Local winds.
1. Permanent winds: The trade winds, westerlies and easterlies are the permanent winds. These blow constantly throughout the year in a particular direction.
2. Seasonal winds: These winds change their direction in different seasons. For example, monsoons in India.
3. Local winds: These blow only during a particular period of the day or year in a small area. For example, land and sea breeze.
Q.8. What is greenhouse effect? Which gas is responsible for greenhouse effect?
Ans: The carbon-dioxide and water vapours in the lower layers of the atmosphere absorb the heat radiated from the earth’s surface and keep the atmosphere warm even during the night. This is known as “the greenhouse effect.” Carbon Dioxide is responsible for the greenhouse effect.
Q.9. What is the significance of Oxygen?
Ans: Oxygen is the second most plentiful gas in the air. It is important because of the following reasons:
(a) Humans and animals take oxygen from the air as they breathe.
(b) Green plants produce oxygen during photosynthesis.
(c) Oxygen is essential for fire. It causes rusting of iron and some other metals.
Q.10. What is the importance of Nitrogen for plants?
Ans: Plants need nitrogen for their survival. They cannot take nitrogen directly from the air. Bacteria, that live in the soil and roots of some plants, take nitrogen from the air and change its form so that plants can use it.
Q.11. What are the factors responsible for variations in atmospheric pressure?
Ans: The variations in the atmospheric pressure is due to the following factors:
(a) Density of the air.
(b) Temperature of the air.
(c) Height of a place above the sea level.
Q.12. Why are poles covered with snow?
Ans: The amount of insolation decreases from the equator towards the poles. That is why poles are covered with snow.
Q.13. Why is rainfall important?
Ans: Rainfall is important because of the following reasons:
(a) It is essential for the survival of plants and animals.
(b) It bring fresh water to the earth’s surface.
(c) If rainfall is less, water scarcity and drought occur. On the other hand if it is more, floods take place.
Long Answer Type Questions
Q.1. Explain different layers of atmosphere.
Ans: Different layers of atmosphere are explained under following heads:
1. Troposphere: (i) It is the most important layer of the atmosphere having average, of about height 13 km.
(ii) Almost all the weather phenomena like rainfall, fog and hailstorm occur in this layer.
2. Stratosphere: (i) This layer is almost free from clouds and associated weather phenomenon, making conditions most ideal for flying aeroplanes.
(ii) It extends up to a height of 50 km.
3. Mesosphere: (i) It extends up to the height of 80 km.
(ii) Meteorites burn up in this layer on entering from the space.
4. Thermosphere: (i) In thermosphere temperature rises very rapidly with increasing height.
(ii) It helps in radio transmission. In fact, radio waves transmitted from the earth are reflected back to the earth by this layer.
5. Exosphere: (i) Its the uppermost layer of the atmosphere.
(ii) Light gases like helium and hydrogen float into the space from here.
Q.2. Name and explain the different types of rainfall.
Ans: The different types of rainfall are given below:
(i) Orographic Rainfall: When moisture-laden wind blowing from sea strikes against a mountain, it is forced to rise up. The rising air cools and condensation takes place resulting in rain. This type of rainfall is called relief rainfall or orographic rainfall as it occurs due to the presence of mountain which forces the air to rise up.
(ii) Convectional Rainfall: This occurs when earth’s surface heats the air over it. Therefore, it goes on rising in the form of currents. These convectional currents while rising, pick up moisture and after they reach a considerably high altitude. The moisture cool down and condense to form clouds. Condensed drops of water then fall on the earth’s surface as convectional rainfall.
(iii) Cyclonic Rainfall: In a cyclone, the wind from high pressure areas on the outside spirally rushes towards the low pressure centre making a depression. The air in this depression is forced to rise up as its outward movements are checked by the in-blowing wind. The rising air condenses sufficient amount of water vapour and drops as rain. This is called Cyclonic Rainfall.
Q.3. Describe the impact of atmosphere on the earth.
Ans: Impact of atmosphere:
1. Atmosphere is responsible for the weather and climate phenomena occurring on the earth.
2. All the circulatory movements between lithosphere and hydrosphere pass through the atmosphere.
3. Atmospheric layers act as a shield and protect the earth against the ultraviolet radiations (UV rays), space debris and provides a greenhouse effect for controlling temperature.
4. It protects water from escaping into space through the process of hydrological cycle.
5. It moderates the impact of solar radiation on the earth.
Q.4. Differentiate between weather and climate.
Q.5. What were the reasons responsible for the damage caused by the super cyclone which occured in Odisha on 17-18 October 1999?
What was the extent of destruction caused by the super cyclone of Odisha?
Ans: The damages caused by the super cyclone were mainly due to three factors:
(a) Wind velocity: The winds of upto 260 km per hour lasted for over 36 hours. These high velocity winds uprooted trees and damaged the kutcha houses.
(b) Rain: Heavy rain occurred under the influence of the cyclone for 3 days continuously which led to flooding in the major rivers of Odisha.
(c) Tidal surge: The cyclonic winds caused tidal waves that swept 20 km inland and brought massive destruction to the coastal areas.
Q.6. “Temperature in cities is higher than that of villages.” Explain.
Ans: The concrete and metals in buildings and the asphalt of roads get heated up during the day. This heat is released during the night. Also, the crowded high rise buildings of the cities trap the warm air and thus raise the temperature of the cities.
Q.7. List two factors which affect the difference in temperature at various places on earth.
Ans: Factors which affect the difference in temperature at various places on earth are:
(a) Closeness to the Equator or the poles: The places close to the equator receive more heat energy as compared to the poles.
(b) Altitude: Temperature decreases with the increase in altitude. Thats why hill stations are colder than plain lands.
Higher Order Thinking Skill
Q.1. What precautionary measures need to be taken against cyclones?
Ans: Some precautionary measures need to be taken against cyclones.
(i) Planting trees of belts along the coastline, to act as a buffer zone.
(ii) Building stilted houses.
(iii) Proper roof should be constructed so that the winds cannot blow the roofs off.
(iv) People should also move to safer areas soon after a cyclone warning is heard.
Q.2. What are the different kinds of pollutants found in the atmosphere?
Ans: Different kinds of pollutants found in the atmosphere are:
Solid Pollutants: It consist of dust and bacteria.
Gaseous Pollutants: In consist of carbon monoxide and smoke.
Q.3. How does the balance of carbon dioxide in the atmosphere gets disturbed?
Ans: The amount of carbon dioxide released by humans or animals seems to be equal to the amount used by the plants which make a perfect balance. However, the balance is upset by burning of fossil fuels such as coal and oil. They add billions of tons of carbon dioxide into the atmosphere each year. As result, the increased volume of carbon dioxide is affecting the earth’s weather and climate.
Value Based Questions
Q.1. How does nature balance our life?
Ans: Nature balance our life. Plants use carbon dioxide to make their food. They release oxygen which is used by human being or animals and essential for their survival. It seems to be equal to the amount used by plants which makes a perfect balance.
Q.2. Give reason why do astronauts wear special protective suits when they go to moon? If they do not wear such suit what will happen?
Ans: On the moon there is no air. Hence due to lack of air there is no pressure.
Astronauts have to wear special suits filled with air when go to the moon. If they do not do so, the center pressure exerted by the body of the astronauts would make the blood vessel burst.
OBJECTIVE TYPE QUESTIONS
I. Fill in the blanks:
1. The blanket of air surrounding the earth is called _______.
2. The upper limit of the troposphere is called the ________.
II. Tick the correct (✔) and cross (x) the wrong statements;
1. Atmosphere is a layer of gases surrounding the earth.
2. Carbon dioxide is a gas which has atoms of both carbon and oxygen.
3. Troposphere is the uppermost layer of the atmosphere.
4. In the mesosphere the temperature of air increases with increase in height.
III. Match the following:
|Column I||Column II|
|(A) Thermometer||(iv) Measures the temperature|
|(B) Barometer||(iii) Shows the direction of wind|
|(C) Rain Gauge||(i) Measures the atmospheric pressure|
|(D) Wind vane||(ii) Measures the amount of rainfall|
Multiple Choice Questions
Choose the correct option:
1. The amount of solar energy received by the earth is called _______.
(b) Terrestrial Radiation.
(c) Solar Radiation.
Ans: (c) Solar Radiation.
2. The degree of hotness or coldness of air is known as its _______.
(a) Atmospheric pressure.
Ans: (c) Temperature.
3. Which phenomenon does not occur when air is heated?
(a) It expands.
(b) It comes down.
(c) It becomes lighter.
(d) It goes up.
Ans: (b) It comes down.
4. The name of instrument used to measure temperature is ________.
(a) Rain gauge.
(b) Wind vane.
Ans: (d) Thermometer.
5. The temperature at which air get saturated is called ________.
Ans: (c) Dewpoint.