7.Chapter4.Geo.Air Around Us

                              Chapter 4.Geography 
      
Chapter 4.Geography.
Air Around Us

Keywords:-

1. Global Warming : The gradual increase in the overall temperature of the earth’s atmosphere.

2. Humidity : Amount of water vapors in the atmosphere.

3. Monsoons : Seasonal reversal of the wind direction according to the change in season.

4. Photosynthesis : Plants absorb carbon dioxide in the presence of sunlight and turn that energy into food.

Something To Do:-

A. Tick the correct option.

1. In normal lapse rate, temperature decreases at the rate of 1 degree Celsius with every-

Ans :-  165m asend.

2. Which layer is safe for flying aircrafts?

Ans :-  Stratosphere.

3. The role of ion-particles in the ionosphere is to-

Ans :-  Enable wireless communication.

4. Which one of the following is the main cause of global warming?

Ans :-  Air pollution.

5. Smog causes-

Ans :-  Breathing problems.

B. Fill in the blanks.

1. Atmosphere  mainly composed of three major gases-nitrogen, oxygen and carbon dioxide.

2. Gases like argon, helium, methane, etc., are present in small amounts in the air.

3. All weather phenomena occur in the troposphere.

4. Atmospheric conditions over a long period of time and a larger area is called climate.

5. The normal air pressure at sea level is 1013 millibar.

C. Match the following:

1. Mono-oxide gas  Most harmful gas present in the atmosphere.

2. Weather  Atmospheric conditions for a specific place covering a short period of time.

3. Barometer  An instrument to measure atmospheric pressure.

4. Atmospheric Pressure  Weight or pressure exerted by the air.

5. Rainfall  The falling of water drops on the earth’s surface.

D. Answer the following questions in brief.

1. Name the layers of the atmosphere.
Ans :- The layer of atmosphere are Troposphere, Stratosphere, Mesosphere,Thermosphere.

2. How do plants absorb nitrogen?

Ans :-  Plants absorbs nitrogen through roots from the soil.

3. What is the importance of water vapours in the atmosphere?

Ans :-  The importance of water vapours in the atmosphere is to get condensed to form clouds.

4. Name the different variables of atmosphere.

Ans :-  The different variables of atmosphere are temperature, humidity and rainfall.

5. What type of climate does India have?

Ans:-  India have monsoonal climate.

E. Answer the following questions.

1. What is the importance of carbon dioxide and oxygen for living beings?

Ans:-  Carbon dioxide is an important gas in maintaining the life cycle of over the earth. The carbon dioxide gas absorbs heat of the sun and warms up the lower atmosphere of the earth’s surface. The green plants draw this carbon dioxide from the atmosphere and utilize it during the process of photosynthesis.
Oxygen is important for all living organisms whether human beings or animals inhale oxygen from the surroundings air to stay alive. Thus, oxygen is known as a life supporting gas.

2.Name three major sources of pollutants in the air. Also state the ill-effects off these air pollutants.

Ans :-  The atmosphere continuously receives man-made substances of both solid and gadeous nature largely due to multiple human activity. For example, plying automobiles in cities releases gaseous pollutants like carbon-mono-oxide, sulpher dioxide and lead particles causing air pollution which in turn, is a cause of several diseases. Volcanic eruptions in some countries also add solid and gaseous substances in large quantity to the atmosphere. Sometimes, forest fires add pollutants and cause further damage to the atmosphere.

3. What is the importance of ozone gas? Why is global warming a threat to life on the earth?

Ans:-  A special form of oxygen called ozone is found in the stratosphere. This ozone layer is very important as it acts as a filter and absorbs harmful ultraviolet sun rays from reaching the earth’s surface. This layer, therefore, acts as a shield over the earth’s surface. In the absence of the ozone gas in the atmosphere, life would have been impossible on the surface of the earth.
Since, the carbon dioxide has a property to absorb heat, it increases temperature of the atmosphere, which, in turn, increases the temperature over the earth’s surface. This is the cause of global warming, which is threatening the life support system of this planet.

4. How is rainfall caused? Explain it with the help of a diagram.

Ans:-  As the hot air raises, it reaches high in the atmosphere it cools down due to the presence of low temperature there. Thus, the water present in the form of water vapours condenses into tiny droplets of water or crystals of ice. In due course of time, these tiny particles join together and form clouds. Due to further cooling. These tiny condensed droplets join and form larger droplets. In the course of time, these droplets became so heavy that the air cannot hold them. Hence, they fall down as rainfall or snowfall, depending upon the region.

5. Write the difference between weather and climate.

Ans:-  Weather refers to the state of atmosphere that includes its temperature, pressure and humidity for a specific place and for a short period of time. Weather may change in different places of thee same city or locality.
On the other hand, climate refer to the state of atmospheric condition that includes temperature, rainfall, pressure over a long period of time and covers a larger area, e.g. the climate of India is monsoonal.

Inside Questions:-

1. What is Atmosphere?

Ans:-  The earth is surrounded by a thick layer of air which is a mixture of several transparent gases is called atmosphere.

2. What is the effect of ultraviolet rays of the Sun?

Ans:-  The ultraviolet rays of the Sun cause skin cancer and different kinds of allergies.

3. What is Smog?

Ans:-  Smog is a type intense air pollution.

4. Define Millibar.

Ans:- The unit of air pressure is known as millibar.

5. Define Barometer.

Ans:-  The pressure or weight of air is measured by means of an instrument called barometer.

6. Define Wind.

Ans:-  The natural movement of air from high pressure to a low pressure is called wind.

7. What is Rain Gauge?

Ans:-  The rainfall can be measured with the help of an instrument called rain gauge. The unit of measuring rainfall is centimeter or millimeter.

8. Define:-

1. Troposphere.

 Ans:-  The lowest region of the atmosphere, extending from the earth’s surface to a height of about 6-10 km is called troposphere.

2. Stratosphere.

Ans:-  The layer of the earth’s atmosphere above the troposphere, extending to about 50 km above the earth’s surface is called stratosphere.

3. Mesosphere.

Ans:-  The region of the earth’s atmosphere above the stratosphere and below the thermosphere, between about 50 and 80 km in altitude is called mesosphere.

4. Thermosphere.

Ans:-  The region of earth’s atmosphere above the mesosphere is called thermosphere.

9. What is Normal Lapse Rate?

Ans:-  In the troposphere, on an average, the temperature decreases at a rate of 1 degree Celcius with every 165 m ascend.

10. What is Tropopause?

Ans:-  The tropopause is the boundry in the earth’s atmosphere between the troposphere and the stratosphere.

11. Which gas is known as life supporting gas?

Ans:-  Oxygen.