Important Questions: Air | Social Studies (SST) Class 7 PDF Download

• Permanent winds
• Seasonal winds
• Local winds

• The most prevalent gas, nitrogen, makes up around 78 per cent of the atmosphere.
• The next important element is oxygen, which makes up about 21% of the atmosphere’s total air mass.
• Carbon dioxide and argon make up 0.93 and 0.03 per cent, respectively.
• In addition, trace amounts of other elements, including helium, ozone, hydrogen, and tiny dust particles, are also present.

Q3: Using the “super cyclone” in Odisha as an example, describe the ferocity of a cyclone.
Ans: Cyclones from the Bay of Bengal are common in Odisha, which lies on the eastern seaboard of India.

• On October 17–18, 1999, and again on October 29, Odisha was affected by cyclones.
• The ‘depression’ that gave rise to the cyclone began in the Gulf of Thailand close to Port Blair.
• On October 25, it headed northwest before intensifying into a super cyclone and making landfall in Odisha.
• A 36-hour period of up to 260 km/hr winds was experienced.
• Trees, Kutcha homes, rooftops, industrial sheds, etc., were all uprooted or blown away.
• Communication and power cables were damaged.
• Major rivers were inundated by persistent rain. Twenty-eight coastal towns and 20 km of interior regions were destroyed, including the metropolis areas of Cuttack and Bhubaneshwar.
• Paddy crops, fruit and vegetable crops, and agricultural land rendered barren owing to salination were all damaged by 7–10 m high tidal surges.
• Thirteen million individuals were impacted. There was also a huge loss of animals.
• Mangrove forests in Paradeep and Konark, as well as teak, sal, and bamboo plantations, all perished.

Q4: Why does it rain? What occurs when rainfall is abundant?
Ans: The definition of rainfall is as follows:

• Rain is defined as precipitation that falls in liquid form on the earth’s surface.
• Condensed gases that ascend above the ground owing to the strong wind pressure and descend as liquid droplets on the earth’s surface are the causes of this phenomenon.
• Gravity is what causes rain to fall on earth.
• Groundwater is mostly sourced by rainfall.
• Floods happen when there is an excess of rainfall.

Q5: Why does the temperature in cities differ from that in rural areas?
Ans: Due to the following factors, cities tend to be warmer than rural areas:

• The natural habitat of people is in villages. Cities are larger, more contemporary versions of villages with denser populations. Cities are therefore extremely populated and have higher levels of pollution. Gases released by companies and automobiles are to blame for this pollution. These gases contribute to the cities’ increasing temperatures.
• The temperature of cities is higher than that of villages because of the asphalt on roads and the concrete and metal of buildings, which absorb heat during the day and release it at night.
• Additionally, the hot and warm air is constrained by the towering structures seen in cities, raising the temperature.

Q6: Describe the many types of atmospheric layers.
Ans: There are five components to the atmosphere:

• Troposphere: The first and foremost layer of the atmosphere is called the troposphere. The troposphere contains various gases in addition to the air we breathe. The troposphere rises to a typical altitude of around 13 km. This layer is where all weather-related phenomena occur.
• Stratosphere: After the troposphere is the stratosphere. The stratosphere is present up to a height of approximately 50 kilometres. The stratosphere is where aeroplanes fly since it is virtually completely free of clouds and meteorological occurrences. Additionally, this layer includes ozone gas, which shields the planet from the sun’s harmful radiation.
• Mesosphere: The mesosphere begins where the stratosphere terminates and reaches a height of 80 km. After entering the atmosphere, meteorites from space burn up here.
• Thermosphere: In this area of the atmosphere, the temperature rises more quickly as altitude rises. It helps with radio transmission since the ionosphere is present in this stratum. It stretches between 90 and 400 kilometres above sea level.
• Exosphere: The exosphere is the topmost and last layer of the atmosphere. It has air inside. Here, helium and hydrogen are typical.

Q7: Give a definition of wind and describe its many types.
Ans: The wind is the term used to describe the flow of air from high-pressure regions to low-pressure regions. There are three main categories of wind:

• Permanent winds: Wind that blows in the same direction all year long is referred to as permanent wind. Permanent winds include trade winds, easterlies, and westerlies.
• Seasonal winds: Seasonal winds are winds that alter their direction with the changing seasons. Monsoon season, for instance.
• Local Winds: Local winds are winds that are present for a brief time in a particular location. 

Q8: Write a brief essay about the atmospheric pressure distribution.
Ans: The weight of the air exerts air pressure on the earth’s surface. This air pressure is uneven and changes at different locations. Here is an explanation of how air pressure is distributed:

• As the atmosphere rises in altitude, the atmospheric pressure rapidly decreases. The air pressure is lowest at sea level and falls as one rises in altitude.
• The temperature of the air significantly influences the pressure of the air at a specific location. The air exerts less pressure, and the hotter it is. Due to this, the air temperature rises in areas with greater temperatures. This aids in establishing a region of low pressure. Similarly, increased air pressure is felt in locations with lower temperatures.

• 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.

Q11: What is the connection between pressure and temperature?
Ans: The local temperature affects the distribution of air pressure:

• High temperatures cause the air to warm up and ascend. A low-pressure region results from this.
• Cloudy sky and rain are correlated with low pressure.
• The air is cold and heavy in low-temperature places. Therefore it sinks. A high-pressure region results from this.
• Clear, bright skies are related to high pressure.
• Air always moves from locations of high pressure to those of low pressure.

Q12: What is the atmosphere?
Ans: The term “atmosphere” refers to the cloud of air that envelops the planet. The bulk of the atmosphere is made up of nitrogen and oxygen, with smaller amounts of other gases, including carbon dioxide, helium, ozone, etc. The environment on earth is necessary for the existence of every living thing.

Q13: Name three types of rainfall.
Ans: Here are the three categories of rainfall:

• Cyclonic rainfall
• Convectional rainfall
• Orographic rainfall

Q14: How does nature balance our life? What is the result if this balance is disturbed?[V. Imp.]
Ans: 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.

Q15: Write a short note on the distribution of air pressure in atmosphere. [Imp.]
Ans: 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. Horizonally 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.