Q 1 – What do you understand by atmosphere?
Ans. The atmosphere is composed of gases, water vapour and dust particles. The proportion of gases changes in the higher layers of the atmosphere in such a way that oxygen will be almost in negligible quantity at the height of 120 km. Similarly, carbon dioxide and water vapour are found only up to 90 km from the surface of the earth.
Q 2 – What are the elements of weather and climate?
Ans. Weather is conditions of temperature, humidity, pressure, etc at a given point of time while climate is condition of these elements for a longer period of time. Following are the important elements of weather and climate: Temperature: It affects weather as well as climate.
- Pressure: Pressure keeps on decreasing with increase in height.
- Wind: The flow of wind also affects weather and climate.
- Humidity: Clouds and rain are important factors of climate
Q 3 – Describe the composition of atmosphere.
Ans. The atmosphere is composed of gases, water vapour and dust particles. Nitrogen constitutes 78.8%, oxygen contributes 20.94% and argon contributes 0.93% in atmosphere. Other gases include carbon dioxide, helium, ozone, methane, hydrogen, krypton, xenon and neon, etc. Nitrogen and oxygen together constitute 99% of the atmosphere. Neon, krypton, xenon are scarce gases. The proportion of gases changes in the higher layers of the atmosphere in such a way that oxygen will be almost in negligible quantity at the height of 120 km. Similarly, carbon dioxide and water vapour are found only up to 90 km from the surface of the earth.
Q 4 – Why is troposphere the most important of all the layers of the atmosphere?
Ans. The troposphere is the lowermost layer of the atmosphere. Its average height is 13 km and extends roughly to a height of 8 km near the poles and about 18 km at the equator. It is most important layer of the atmosphere because:
- Thickness of the troposphere is greatest at the equator because heat is transported to great heights by strong convectional currents.
- This layer contains dust particles and water vapour.
- All changes in climate and weather take place in this layer.
- The temperature in this layer decreases at the rate of 1°C for every 165m of height.
- All biological activities take place in this layer.
Q 5 – Draw a suitable diagram for the structure of the atmosphere and label it and describe it.
Ans. The atmosphere consists of different layers with varying density and temperature. Density is highest near the surface of the earth and decreases with increasing altitude. The atmosphere is divided into five different layers depending upon the temperature condition.
They are: troposphere, stratosphere, mesosphere, thermosphere and exosphere
1. Troposphere: The troposphere is the lowermost layer of the atmosphere. Its average height is 13 km and extends roughly to a height of 8 km near the poles and about 18 km at the equator. Thickness of the troposphere is greatest at the equator because heat is transported to great heights by strong convectional currents. This layer contains dust particles and water vapour. All changes in climate and weather take place in this layer. The temperature in this layer decreases at the rate of 1°C for every 165m of height.
2. Stratosphere: The stratosphere is found above the tropopause and extends up to a height of 50 km. One important feature of the stratosphere is that it contains the ozone layer. This layer absorbs ultra-violet radiation and shields life on the earth from intense, harmful form of energy.
3. Mesosphere: The mesosphere lies above the stratosphere, which extends up to a height of 80 km. In this layer, temperature starts decreasing with the increase in altitude and reaches up to minus 100°C at the height of 80 km.
4. Ionosphere; The ionosphere is located between 80 and 400 km above the mesopause. It contains electrically charged particles known as ions, and hence, it is known as ionosphere. Radio waves transmitted from the earth are reflected back to the earth by this layer.
Temperature here starts increasing with height.
5. Exosphere: The uppermost layer of the atmosphere above the thermosphere is known as the exosphere. This is the highest layer but very little is known about it.
Q 6 – By which elements is atmosphere made up of?
Ans. Atmosphere is made up of gases, water vapours and dust particles.
Q 7 – What percent of earth mass is constituted by air and it is confined to what height?
Ans. The air is an integral part of the earth’s mass and 99 percent of the total mass of the atmosphere is confined to the height of 32 km from the earth’s surface.
Q 8 – How does the composition of air keep changing in upper layers of the earth?
Ans. The proportion of gases changes in the higher layers of the atmosphere in such a way that oxygen will be almost in negligible quantity at the height of 120 km. Similarly, carbon dioxide and water vapour are found only up to 90 km from the surface of the earth.
Q 9 – Ozone is an important constituent of atmosphere How?
Ans. Ozone is another important component of the atmosphere. It is found between 10 and 50 km above the earth’s surface and acts as a filter. It absorbs the ultra-violet rays radiating from the sun. It prevents them from reaching the surface of the earth
Q 10 – What do you mean by tropopause?
Ans. The zone separating the troposphere from stratosphere is known as the tropopause.
Q 11 – What is an important feature of stratosphere?
Ans. The stratosphere is found above the tropopause and extends up to a height of 50 km. One important feature of the stratosphere is that it contains the ozone layer. This layer absorbs ultra-violet radiation and shields life on the earth from intense, harmful form of energy.
Q 12 – What is an important feature of troposphere?
Ans. The troposphere is the lowermost layer of the atmosphere. Its average height is 13 km and extends roughly to a height of 8 km near the poles and about 18 km at the equator. Thickness of the troposphere is greatest at the equator because heat is transported to great heights by strong convectional currents. This layer contains dust particles and water vapour. All changes in climate and weather take place in this layer. The temperature in this layer decreases at the rate of 1 C for every 165m of height.
Q 13 – Name the gases found in atmosphere.
Ans. The atmosphere is composed of gases, water vapour and dust particles. Nitrogen constitutes 78.8%, oxygen contributes 20.94% and argon contributes 0.93% in atmosphere. Other gases include carbon dioxide, helium, ozone, methane, hydrogen, krypton, xenon and neon, etc.
Q 14 – Explain important features of ionosphere.
Ans. The ionosphere is located between 80 and 400 km above the mesopause. It contains electrically charged particles known as ions, and hence, it is known as ionosphere. Radio waves transmitted from the earth are reflected back to the earth by this layer. Temperature here starts increasing with height
Q 15 – Write a short note on water vapours.
Ans. Water vapour:
- The amount of water vapour decreases with the altitudes. In warm and wet tropics, it accounts for 4% of the air by volume whereas in dry and cold areas of deserts and polar regions, it may be less then 1% of the air.
- It also decreases from the equator towards the poles.
- It absorbs parts of the insolation received from the sun and preserves the earth’s radiated heat and thus acts as a blanket by allowing the earth neither to become too hot nor too cold.
Q 16 – Explain about dust particles.
Ans. Dust particles:
- Dust particles are concentrated in the lower layers of the atmosphere but sometimes conventional currents take them to the higher height.
- Dust particles includes sea salts, fine soil, smoke, ashes, pollens, dust, disintegrated particles of meteors.
- Dust particles and salt particles act as a hygroscopic nuclei around which water condenses into water vapour to produce clouds.
- Dust particles produce optical phenomenon which makes the sky look beautiful at dawn and dusk.
- Sky looks blue due to the presence of dust particles and water vapour which are scattered in the atmosphere.
Q 17 – Write about elements of weather and climate in detail.
Ans. The main elements of atmosphere which are subject to change and which influence human life on earth are temperature, pressure, winds, humidity, clouds and precipitation. These elements act and react on each other. These elements determine the direction and speed of wind, amount of sunlight received, cloud formation and amount of rainfall. These in turn affect weather and climate. These factors behave differently in different places. All these elements are affected by a number of factors in turn. For example, temperature is affected by latitude and height; humidity is affected by distance from the sun and pressure is affected by height from sea level.
Q 18 – Write about the structure of atmosphere in detail.
Ans. Structure of Atmosphere: The layers of atmosphere differ from one another with respect to density and temperature. On the basis of chemical composition the atmosphere is mainly divided into.
- Homosphere
- Hetrosphere
1. Homosphere:
- It extends upto 90 km.
- It is uniform in chemical composition.
- It consists of three layers
- Troposphere
- Tropopause:
- Stratosphere
- Mesosphere
Troposphere:
- Lower most layer of atmosphere
- Average height is 13 km although it is roughly 8 km.
- The thickness of troposphere is greater at equation due to upward transportations of heat by conventional currents. This layer consists of dust particles and water vapours.
- The temperature decrease with height in this layer at a rate ldegree for every 165 m. this is known as Normal Lapse Rate.
- It is layer is important for all biological activities besides that all climatic and weather conditions takes place in this layer.
Tropopause:
- The upper limit of troposphere separating it from stratosphere is called tropopause. It is very unstable at a thin layer and very thin layers of 1.5 km thickness.
- The temperature of tropopause is -80degree centigrade censius at equator and -40 degree centigrade at poles.
- The jet planes at the other activities occur in this layer.
Stratosphere:
- It extends upto 50km.
- It is thicker at poles then at equator.
- The temperature is almost constant in its lower portion upto 20 km and their it gradually increases upto 50 km due to the presence of Ozone which absorbs UV rays.
- The temperature rises in the upper limits of the stratosphere as there are no clouds, no conventional currents, no dust particles and the air moves in the horizontal direction. The upper’ limit of stratosphere is called stratosphere which has concentration of Ozone gas.
Mesosphere:
- It extends from 50* to 90 km.
- Temperature decreases with height in this layer and false upto minus 100 degree centigrade at a height of 80-90 km. this is due to the clouds in high latitudes.
- The upper limit of Mesosphere is called as Mesopause.
2. Hetrosphere:
- It has heterogeneous chemical.
- It consist of two layers
- Ionosphere
- Exosphere
Ionosphere
- It extends from 80 to 400 km above the mesopause.
- It contains electrically charged particles known as ions
Exosphere
- It is the uppermost layer of the atmosphere above the thermosphere.
Q 19 – What would happen if there is no ozone in the atmosphere?
Ans. It is the special variety of oxygen gas which is found in small quantity in atmosphere between 10 to 15 km above the earth surface. It acts as a filter and absorbs UV radiation from the sun and prevents them from reaching the earth surface. If ozone is not there, then UV rays will reach the surface of the earth. There will be extreme skin problems, instances of cancer and in all probabilities life would not have been possible on the earth.
Q 20 – What is the role of dust particles in atmosphere?
Ans. The atmosphere has sufficient capacity to keep small solid particles which may originate from different sources and includes sea salts, fine soil, smoke soot, ash, polan, dust and disintegrated particles of meteors. Dust and solid particles act as hygroscopic nuclei around which water vapour condenses to produce clouds.
Q 21 – How is the atmosphere held to the earth?
Ans. The atmosphere is held to the earth by the force of gravity.
Q 22 – What is heterosphere?
Ans. The layer of the atmosphere 90 km above the surface of the earth where the composition begins to change with a progressive increase in the lighter gases, is called heterosphere.
Q 23 – Which are the major constituents of clean dry air of atmosphere?
Ans. Oxygen and nitrogen are the major constituents of clean dry air of the atmosphere.
Q 24 – Which gas of the atmosphere does not take part in a chemical reaction?
Ans. Argon’ does not take part in a chemical reaction.
Q 25 – What are aerosols?
Ans. Aerosols are huge amounts of s0lid and liquid particles present in the atmosphere.
Q 26 – Which gas despite its small percentage is crucial in atmospheric processes?
Ans. Carbon dioxide is an important gas in the atmospheric processes
Q 27 – What is the atmosphere?
Ans. The atmosphere is a gaseous envelope extending thousands of kilo meters above the earth’s surface.
Q 28 – What energises the atmosphere?
Ans. The atmosphere is energised by the sun.
Q 29 – Where does much of life exist on the earth?
Ans. Much of life exists at the bottom of the atmosphere where it meets the lithosphere and the hydrosphere.
Q 30 – Name two broad layers of the atmosphere.
Ans. Homosphere and heterosphere are two broad layers of the atmosphere.
Q 31 – Name the three thermal layers of the homosphere.
Ans. Troposphere, stratosphere and mesosphere.
Q 32 – What is wind?
Ans. The horizontal motion of the air is known as wind.
Q 33 – Mention some forms of precipitation.
Ans. Rain, hail, sleet or snow are some forms of precipitation.
Q 34 – Which gas acts as a filter and protects us from ultraviolet rays?
Ans. Ozone gas protects us from the ultraviolet rays and acts as a filter
Q 35 – Which layer transmits the radio waves?
Ans. Ionosphere.
Q 36 – Name the gas which is found in the upper part of the atmosphere.
Ans. Hydrogen.
Q 37 – What are the two causes of depletion of the ozone layer?
Ans. Use of carbons and deforestation are the two causes of depletion of the ozone layer.
Q 38 – Name the gas which is most essential for life.
Ans. Oxygen.
Q 39 – What are the principal elements of weather and climate?
Ans. Temperature, pressure, wind, moisture and precipitation are the principal elements of weather and climate.
Q 40 – Why do the jet aircraft fly through the lower stratosphere?
Ans. Because it provides the easiest flying conditions. It is the layer of calm and clean air. There is no water vapour and clouds are present.
Q 41 – What are the constituents of dust particles?
Ans. Smoke-soot, ash, pollen are the main constituents of dust particles.
Q 42 – What is the weather?
Ans. The cumulative effect of wind, temperature, pressure, clouds, humidity and precipitation is called weather.
Q 43 – What is the role of elements of weather?
Ans. They influence temperature and precipitation.
Q 44 – Why are the vapour and dust particles important variables of weather and climate?
Ans. The water vapour and dust particles are important variables of weather and climate because they are the source of all forms of condensation and principal absorbers of heat received from the sun or radiated from the earth. Besides, they affect the stability of the atmosphere.
Q 45 – What is meant by a normal lapse rate?
Ans. The temperature decreases with altitude because the atmosphere is heated more by the heat radiated from the earth’s surface. Wanner air lying under the cooler air goes up or turns downward. In this layer, the temperature decreases vertically at a rate of 0.65°C per 100 metres. It is called the normal lapse rate.
Q 46 – What is homosphere?
Ans. The atmospheric layer up to an altitude of 90 km. above the surface of the earth is generally called homosphere. It is uniform in term of these major gases – nitrogen, oxygen and argon. In addition, it also contains some rare gases like neon, krypton and xenon.
Q 47 – Name the gases and other materials which compose the atmosphere.
Ans. Nitrogen, oxygen and argon are the most important gases of the atmosphere. In addition, it contains gases like carbon dioxide, neon, helium, ozone, hydrogen, methane, krypton and xenon. Besides, there are also present huge amounts of solid and liquid particles collectively called aerosols.
Q 48 – Discuss the properties of nitrogen gas.
Ans. Nitrogen is the most abundant gas of the atmosphere. By volume, it constitutes 78.8% of the total gases present in the atmosphere. Nitrogen does not easily enter into chemical union with other substances but gets fixed into the soil. It serves mainly as diluent or dissolver. It regulates combustion.
Q 49 – What is the importance of carbon dioxide on the earth?
Ans. By volume carbon dioxide constitutes 0.03% of the total gases of the earth’s atmosphere. Although it forms a small portion, it is an important gas in the atmospheric processes. It can absorb the heat and thus allows the lower atmosphere to be warmed up by heat radiation coming from the sun and from the earth’s surface. Green plants in the process of photosynthesis utilise carbon dioxide from the atmosphere.
Q 50 – Explain the difference between weather and climate.
Ans. The weather of any place is the sum total of its temperature, pressure, winds, moisture and precipitation conditions for a short period of time. Climate, on the other hand, is the composite weather conditions over a considerable period of time.
Q 51 – Identify the climatic controls.
Ans. The various climatic controls are given below :
- Latitude or sun.
- Distribution of land and water
- The great semi-permanent high and low-pressure belts
- Winds
- Altitude
- Mountain barriers
- Ocean currents
- Storms of various kinds
Q 52 – What is the importance of the atmosphere for the earth?
Ans. The earth is the only known planet to have life. The atmosphere, which is unlike that of any other planet, encircles and protects the earth. Changes in the composition of the atmosphere are closely associated with the evolution of the earth. One of the most important transition was the increase in oxygen when photosynthetic plants evolved.
The atmosphere is a mixture of gases, the largest proportion of which is nitrogen. However, the most important is oxygen, without which life could not be sustained. The very survival of life processes is associated with the atmosphere.
The influence of the atmosphere on humans particularly is not only direct but also indirect through natural vegetation, soil and topography.
Q 53 – What is tropopause?
Ans. The tropopause is the plane which separates the troposphere and stratosphere. It is the boundary between these two layers. It is a thin transitional zone between two layers.
Q 54 – Explain three major features of the troposphere.
Ans. It is 16 km thick at the equator and 10 km thick at the poles.
- The temperature decreases with the altitude at the rate of l°C per 165 meters.
- Biological activities take place in this layer.
Q 55 – What are the main characteristics of the lowermost layer of the atmosphere?
Ans. The lowermost layer is the troposphere.
- Its average height is 16-18 km.
- All biological activities occur in this layer.
- All the atmospheric processes take place in this layer.
- It is 16 km thick at the equator and 10 km thick at the poles.
Q 56 – What is the difference between condensation and precipitation?
Ans. Condensation is the physical process of the transition of a substance from the vapour to the liquid state, e.g., as a result of cooling or increase of pressure. It occurs in the atmosphere when the air is saturated or when it is cool. Thus, the change of state of the moisture from invisible water vapour to visible liquid (water) or solid (ice or snow ) state is known n as condensation. It is opposite of evaporation.
Precipitation, on the other hand, means ‘throwing down of moisture’. Continuous condensation in the body of the air helps the water droplets to grow in size so that the resistance of the air fails to keep them suspended. In such cases, only an ascending air current can keep them floating in the air. In the absence of such a current, the products of condensation begin to fall on the earth’s surface. The process whereby the water vapour first condenses in the air and then falls on to the earth is called precipitation.
Q 57 – Discuss the principal elements of weather and climate and the major climatic controls.
Ans. The principal elements of weather and climate are temperature precipitation, moisture, pressure and winds. These are called elements because they are the ingredients out of which various weather and climate types are compounded. The temperature and precipitation are the main basic elements to which pressure, winds and other elements are related.
Temperature expresses the intensity of heat. Practically all the heat energy on the earth is the result of insulation or the increasing solar radiation. Unequal distribution of temperature over the earth’s surface causes differences in atmospheric pressure, which causes winds.
Higher the temperature, the greater is the capacity’ of air to hold moisture on cooling. The air is not able to retain all the moisture it gathers while warm. This leads to condensation and precipitation.
Thus, the temperature is the basic element on which other elements of climate depend.
The climatic controls are :
Latitude (or sun), distribution of land and water, the great semi¬permanent high and low-pressure belts, winds, altitude, mountain barriers, ocean currents and storms of various kinds.
Q 58 – Define the atmosphere. Explain its importance to human life.
Ans. The atmosphere is a mixture of air and various gases which envelopes the earth all around. It represents the gaseous realm of the earth. It is held to the earth by the force of gravity.
Importance of atmosphere:
- It contains gases like oxygen (essential for breathing) for man and animals and carbon dioxide for plants.
- By trapping the heat, it acts as a greenhouse. It keeps the earth
warm. - One of its layer, the ionosphere, reflects radio waves back to the earth and makes radio communication possible.
- It protects us from the deadly cosmic rays and meteors which are continuously showered on the earth from outer space.
- All the weather phenomenon take place in the atmosphere. Presence of water vapour in the atmosphere brings many changes such as condensation and precipitation. These processes influence the human life, plants and animals.
- It absorbs ultraviolet rays.
- It acts as an air conditioner by moderating the extremes of heat ‘ and cold.
- It is a storehouse of water vapour.
Q 59 – Discuss the proportion of the constituent gases of the atmosphere.
Ans. The atmosphere is a mixture of various gases. It includes :
Nitrogen (N,), Oxygen (O,), Argon (Ar), Carbon dioxide (CO,), Neon (Ne), Helium (He), Ozone (O,), Hydrogen (H), Methane (CH4), Krypton (Kr) and Xenon (Xe).
Nitrogen (N2): It is a colourless, odourless gas, the main constituent (i.e. 78.8% by volume) of the atmosphere. It is an essential constituent of living organisms. It is an important element for plants.
Oxygen (O,): Constitutes 20.94% of the total volume of the atmosphere. It is the second most abundant gas. It is essential to plant and animal life.
Argon (Ar): It constitutes one per cent volume of the total atmosphere. It is an inert gas, does not take part in any chemical reaction.
Carbon dioxide: It constitutes a very small amount (0.03%). It is an important gas in the atmospheric process. It can absorb heat and thus allows the lower atmosphere to be warmed up by heat radiation from the sun and from the earth’s surface. Green plants in the process of photosynthesis utilise carbon dioxide from the atmosphere.
Neon (Ne): Neon is an inert gaseous element occurring in’ trivial quantities (0.0018%) in the atmosphere
Helium (He): It exists primarily in the sun’s atmosphere. It is an inert element of the atmosphere.
Ozone (03): It is an allotropic form of oxygen (02). Its main concentration lies between 20 to 25 km. from the earth’s surface.
Hydrogen (H): It is the lightest element. It is gaseous and inflammable. It is used in many chemical processes.
