Class 7 Geography Chapter 4 Air Important Questions and Answers
CBSE Class 7 Geography Chapter 4 Air Important Questions and answers cover all the major concepts of the chapter. Solving answers of these important questions help students to revise the Chapter most competently. We prepared these questions as per the latest NCERT book and CBSE syllabus. Practising class 7 important questions before the exam will ensure excellent marks in the exam.
Air Class 7 Geography Important Questions
Very Short Answer Type Question
1: Which among the following sphere suitable for flying aeroplanes.
2: In thermosphere temperature rises very rapidly with increasing height. (T/F)
3: The air pressure is highest at sea level and decreased with height. (T/F)
4: Exosphere is the uppermost layer of the earth.(T/F)
5: The degree of hotness and coldness of the air is known as __________
6. How does carbon dioxide create green house effect? [V. Imp.]
Answer: Carbon dioxide creates greenhouse effect by trapping the heat radiated from the earth.
7. What is the significance of greenhouse gas?
Answer: Without the greenhouse gas the earth would have been too cold to line in.
8. What happens when air is heated?
Answer: When air is heated, it expands, becomes lighter and goes up.
9. What is the nature of cold air?
Answer: It has tendency to go down.
10. Why do green plants use carbon dioxide? [Imp.]
Answer: Green plants use carbon dioxide to make their food and release oxygen.
11. What is an important feature of Stratosphere?
Answer: Stratosphere contains a layer of ozone gas.
12. How is ozone important for us? [Imp.]
Answer: It protects us from the harmful effect of the sunrays.
13. What is temperature?
Answer: The degree of hotness and coldness of the air is known as temperature.
14. What is insolation?
Answer: Insolation is the incoming solar energy intercepted by the earth.
15. Why is there no air pressure on the moon?
Answer: There is no air on the moon and therefore no air pressure.
16. Where is air pressure highest?
Answer: Air pressure is highest at the sea level.
17. How does air move?
Answer: Air moves from high pressure areas to low pressure areas.
18. What is the hot and dry wind of northern planes of India called?
Answer: It is called loo.
19. What is called humidity? [V. Imp.]
Answer: Moisture in the air at any time is called humidity.
20. Why do we feel uncomfortable on a humid day?
Answer: It is because sweat from our body does not evaporate easily.
21. How is flooding of low lying areas caused? [V. Imp.]
Answer: When trees on hill sides are cut, rainwater flows down the bare mountains. This causes flooding of low lying areas.
22. How is a wind named?
Answer: A wind is named after the direction from which it blows.
Short Answer Type Questions
1: Explain the term dynamic environment.
Answer: The physical and biological elements in the environment are dynamic in nature changes take place slowly and suddenly in the nature of landforms. The circulation air and water brings about changes in the climatic conditions in different seasons.
2: Atmosphere plays a dynamic role how?
Answer: Among the four major elements of environment, the atmosphere is most dynamic as changes take place in it not only from one season to another but also over shorter periods of few hours.
3: What is air circulation?
Answer: When air is heated it becomes lighter and goes up. Cold air is denser and heavy that is why it tends to sink down. When hot air rises, cold air from surrounding area rushes there to fill the gap. This is how air circulation takes place.
4: Define insolation.
Answer: Insolation is the incoming solar energy intercepted by the earth. The amount of insolation decreases from the equator towards poles.
5: Name the instrument which measures temperature?
Answer: Temperature is measured with the help of thermometer. Outdoor temperature is measured with the help of mercury thermometer.
6: What do you mean by maximum and minimum temperature?
Answer: Maximum temperature is the highest temperature of the day recorded about 2.00 pm.
7: Define low and high pressure.
Answer: In areas where temperature is high the air gets heated and rises. This creates a low pressure area.In the area having low temperature the air is cold. It is therefore heavy. Heavy air sinks and creates a high pressure.
8: What is meteorology?
Answer: The scientific study of weather is called meteorology.
9: Which layer is free from water vapour and dust particle?
Answer: The stratosphere is free from water vapour and dust particle.
10: Define wind.
Answer: Moving air is called wind. Wind always blows from high pressure to low pressure.
11: Name the different layers of atmosphere?
Answer: The different layer of atmosphere are-troposphere, stratosphere, mesosphere, thermosphere, exosphere.
12: Which layer makes weather phenomena possible?
Answer: Troposphere layer makes weather phenomena possible.
13: Which layer makes radio communication possible?
Answer: Ionosphere layer makes radio communication possible.
14: Which layer protects us from meteors and obsolete satellite from outer space?
Answer: The ionosphere or the thermosphere protects us from meteors and obsolete satellite from outer space.
15: What is moisture?
Answer: This term refers to degree of moisture present in the air .There is a definite limit to the quantity of moisture that can be held by the air at a specific temperature.
16: Define dew point?
Answer: The temperature at which the air becomes fully saturated is known as dew point.
17: What do you mean by absolute humidity?
Answer: The total amount of water vapour that is contained in the air at a given temperature is known as absolute humidity.
18: Define the term relative humidity.
Answer: The ratio between actual amount of water vapour present in the air at a given temperature and the maximum amount of water vapour that the atmosphere can retain at that temperature is known as relative humidity.
19: What is importance of rainfall?
Answer: Rainfall is very important for the survival of plants and animals. It brings fresh water to the earth’s surface. If rainfall is less the it may cause drought on the other hand if it is more floods will takes place.
Long Answer Type Questions
1: Describe the composition of atmosphere.
Answer: The atmosphere consists of mixture of gases having a relatively uniform composition in the lower layer. An average sample of pure dry air consist of nitrogen (78 %), oxygen (21%) and argon (0.9 %), other gases such as carbon dioxide, hydrogen helium and ozone are present in minute quantities. The lower layer of atmosphere also contains water vapour in variable quantities.
2. Give an account of the composition of the atmosphere. [V. Imp.]
Answer: Our atmosphere is composed of mainly two gases—nitrogen (78%) and oxygen (21%). Other gases like carbon dioxide, helium, ozone, orgon and hydrogen are found in lesser quantities. Apart from these gases, tiny dust particles are also present in the air.
3. How do Bacteria help plants use nitrogen? [V. Imp.]
Answer: Nitrogen is essential for the survival of plant. But plants 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.
4. How does nature balance our life? What is the result if this balance is disturbed?[V. Imp.]
Answer: Green plants use carbon dioxide to make their food and release oxygen. Humans or animals release carbon dioxide. 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. But this balance is disturbed by burning of fuels, which add billions of tons of carbon dioxide in the atmosphere. As a result, the increased volume of carbon dioxide is affecting the earth’s weather and climate.
5. Why is temperature in cities much higher than that of villages?
Answer: In cities we find high rise buildings. The concrete and metals in these buildings and the asphalt of roads get heated up during the day. This heat is released during the night.
Another reason is that the crowded high rise buildings of the cities trap the warm air and thus raise the temperature of the cities.
6. Write a short note on the distribution of air pressure in atmosphere. [Imp.]
Answer: Air pressure is the pressure exerted by the weight of air on the earth’s surface. As we go up the layers of atmosphere, the pressure falls rapidly. The air pressure is highest at the sea level and decreases with height. Horizontally the distribution of air pressure is influenced by temperature of air at a given place. In areas where temperature is high the air gets heated and rises. This creates a low pressure area. In areas having lower temperature, the air is cold, hence, it is heavy. Heavy air sinks and creates a high pressure area.
7. Why do astronauts wear special protective suits when they go to the moon?
Answer: Astronauts wear special protective space suits filled with air when they go to the moon. If they did not wear these space suits, the counter pressure exerted by the body of the astronauts would make the blood vessels burst. The astronauts would bleed.
8. How is rainfall important for us? What happens when there is excess rain? [V. Imp.]
Answer: Rainfall is very important for the survival of plants and animals. It brings fresh water to the earth’s surface. If rainfall is less, there is water scarcity which sometime causes drought like situation. If there is excess rain, floods take place which make the life of the affected people miserable.
9. Give an account of the different layers of the atmosphere. [V. Imp.]
Answer: Our atmosphere has five different layers. They are:
- Troposphere: This is the most important layer of the atmosphere with average height of 13 km from the earth. It is in this layer that we find the air that we breathe. Almost all the weather phenomena such as rainfall, fog and hailstorm occur here.
- Stratosphere: This layer extends up to a height of 50 km. It presents the most ideal conditions for flying aeroplanes. It contains a layer of ozone gas which protects us from the harmful effect of the sunrays.
- Mesosphere: This layer extends up to the height of 80 km. Meteorites bum up in this layer on entering from the space.
- Thermosphere: In this layer temperature rises very rapidly with increasing height. Ionosphere is a part of this layer. It extends between 80—400 km. This layer helps in radio transmission. Radio waves transmitted from the earth are reflected back to the earth by this layer.
- Exosphere: It is the uppermost layer where there is very thin air. Light gases such as helium and hydrogen float into the space from here.
10. What is wind? Mention its different types.
Answer: Wind is the movement of air from high pressure area to low pressure areas. It is divided into three types:
- Permanent winds
- Seasonal winds
- 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 winds blow only during a particular period of the day or year in a small area. For example: land and sea breeze. Loo is a local wind which hot and dry and blow in the northern plains of India during summers.