Selina Concise Class 6 Chemistry Chapter 6 Air And Atmosphere Solution

Selina Concise Class 6 Chemistry Solution Chapter No. 6- ‘Air And Atmosphere’ For ICSE Board Students.

                         AIR AND ATMOSPHERE SOLUTION

EXERCISE-I

(1.) WHAT IS ATMOSPHERE?

ANS:- The earth is surrounded by a thick layer of air called the atmosphere that extends upto a height of about 320 kilometers above the surface of the earth .It is called atmosphere.

(2.) WHY CAN’T WE SEE AIR?

ANS:- We cannot see air because it is colourless, odourless, tasteless, transparent gaseous matter.

(3.) WHAT IS WIND?

ANS:- Fast moving air is called Wind.

(4.) WHAT WOULD HAVE HAPPENED IF THERE WOULD HAVE BEEN NO ATMOSPHERE AROUND EARTH?

ANS:- Without atmosphere life could not be possible as atmosphere protects us from harmful gases. We cannot live without air present in atmosphere. The earth would get get so cold at night that we would not be able to survive. We cannot live without atmosphere  around the earth.

(5.) WHY IS AIR CALLED A MIXTURE? GIVE FIVE FACTS IN SUPPORT OF YOUR ANSWER.

ANS:- Air is called mixture because- 1.) Air has no formula, a mixture has no formula whereas compound has a formula.

2.) When air is formed out of its constituents no change in mass and no change in volume takes place.

3.) No energy changes are involved to form air from various gases.

4.) Components of air can be separated by simple physical methods.

5.) Properties of air vary from place to place and time to time. There is more CO2 in towns as compared to villages where more oxygen prevails as compared to towns.

(6.) WHAT ARE THE MAIN COMPONENTS OF AIR? WRITE DOWN THE COMPOSITION OF THREE MAIN GASES PRESENT IN AIR BY VOLUME.

ANS:- Main components of air are- Nitrogen and Oxygen.

Three main gases composition in air by volume are-

Nitrogen-78%,  Oxygen- 21%,   Carbondioxide- 0.04%,  Inert gases- 0.9%

(7) WHAT DO YOU OBSERVE WHEN-

a) ICE COLD WATER IS FILLED IN A GLASS TUMBLER.

ANS:- When Ice cold water is filled in a glass tumbler we will observe that fine water droplets gets deposited on the outer wall  of the glass tumbler. These droplets have certainly not passed through the material of the class tumbler from inside.

b) A BURNING CANDLE IS COVERED WITH AN INVERTED JAR.

ANS:- We will observe that the candle burn more brightly for getting oxygen from air.

C) CARBON DI OXIDE GASS PASSED THROUGH LIME WATER.

ANS:- We will observe that CO2 reacts with water and form calcium carbonate and turns it milky.

d) A BEAM OF LIGHT IS ALLOWED TO ENTER IN A CLOSED DARK ROOM THROUGH A SMALL HOLE.

ANS:- Then we will observe randomly moving dust particles in the beam of light. This confirms the presence of dust particles in the air.

(8.) WRITE THE CHEMICAL NAME OF-

A) LIME WATER- Calcium hydroxide.

B) THE WHITE INSOLUBLE SOLID FORMED ON REACTION OF CABON DI OXIDE WITH LIME WATER.

ANS:- Calcium carbonate.

EXERCISE-II

(1.) NAME TWO IMPORTANT PROCESS SUPPORTED BY OXYGEN PRESENT IN AIR.

ANS:- The two processes are- 1.) Respiration. 2.) Combustion.

(2.) GIVE TWO USES OF THE FOLLOWING COMPONENTS PRESENT IN AIR:

A) OXYGEN:- It is important for respiration and breathing. And it is responsible two most important process that is Respiration and combustion.

B) NITROGEN:- It is present in the soil and used by plants for their growth and formation of protein an important nutrient for animals.It is used to make fertilizers.

c) CARBONDIOXIDE:- Carbondioxide is used by plants to prepare their food by photosynthesis. It is used to prepare fizzy drinks like soda water.

d) WATER VAPOUR:- Water vapour present in the air. It is help to predicting climatic conditions of a particular area. It is varied from place to place and time to time.

(3.)

a) RESPIRATION:- Respiration is a chemical process that takes place in all living beings. In this process oxygen present in air. This result in releaseof energy, carbondioxide and water.

b) PHOTOSYNTHESIS:- Photosynthesis is a process of food processing by green plants taking CO2 from air, water from soil by the roots and in the sunlight with the help of chlorophyll. That’s process is called Photosynthesis.

C) COMBUSTION:- Combustion is a process of burning of substance in oxygen of air completely producing heat and light is called combustion.

(4.) WHAT ARE FUELS? GIVE TWO EXAMPLES OF MODERN FUELS.

ANS:- The substance that are burn in air to produce large amount of energy in the form of heat and light are called fuels.

Examples- CNG,PETROL

(5.)

a) AQUATIC ANIMALS AND PLANTS ARE ABLE TO SURVIVE IN WATER.

ANS:-  Aquatic animals and plants use oxygen dissolved in water to survive. So they can.

b)A BURNING CANDLE STOPS BURNING IF COVERED WITH A GLASS OF WATER.

ANS:- Because for burning a candle oxugen is required. But when covered a glass of water oxygen supply stopped.

c) MOUNTAINEERS AND DIVERS CARRY OXYGEN CYLINDERS WITH THEM.

ANS:- For artificial respiration mountaineers carry oxygen cylinders as at high altitudes, the air is thin and breathing becomes difficult. Also divers carry oxygen cylinder for artificial respiration as there is less oxygen dissolved in water and breathing becomes difficult.

d)WHEN WATER IS HEATED WE SEE BUBBLES RISING UP.

ANS:- The bubbles come from the air dissolved in water. The marine life uses air dissolved water.

(6.) NAME THE PROCESS WHICH MAINTAIN THE BALANCE between OXYGEN AND CARBONDIOXIDE IN THE AIR. HOW IS IT DONE?

ANS:- Respiration and combustion are the process which maintain the balance between oxygen and CO2 in the air.

Respiration is a chemical process that takes place in all living beings. In this process oxygen present in the inhaled air reacts with the digested food material in the body. This results in the release of energy, carbon dioxide and water.

Combustion is a process in which a substance reacts chemically with oxygen and gets oxidized with the release of energy in the form of heat and light . During the process of burning, along with energy CO2 and water vapour are also produced.

(7.) SIMILARITIES AND TWO DIFFERENCES BETWEEN RESPIRATION AND BURNING.

ANS:- 1.) In burning  oxygen is needed to combine with carbon and hydrogen in compound.

2.) In burning CO2 and H2O are formed with release of energy. 

In respiration oxygen is needed to combine with C and H2 of food.

And CO2 , H2O are formed with release of energy.

DIFFERENCES-

  • In burning occurs at higher temperature and in respiration occurs body temperature.
  • Burning is fast process and Respiration is a slow process.

(8.) DEFINE RUSTING. WHAT ARE THE TWO NECEASSERY CONDITIONS FOR RUSTING OF IRON? GIVE THE CHEMICAL NAME OF RUST.

ANS:- Slow conversion of iron into its hydrated oxide in the presence of moisture and air is called rusting.

Two conditions for rusting of iron-  1. Presence of moisture.  2. Presence of air.

Chemical name of rust is hydrated iron oxide.

(9.) HOW  IS AIR USEFUL TO;

A) WATER BOATS:- Air helps movement of water boats.

B) AGRICULTURE:- Air speeds up drying up of agricultural products like grains,pulses fruits etc. Air helps in pollionation of flowers and dispersel of seeds.

c) WINDMILLS:- Windmils work where there is sufficient movement of air.

d) SCOOTER AND CARS:- Air filled tyres of cars move smoothly on road as there is less friction.

(10) STATE THE FULL FORM OF LPG AND CNG. HOW ARE THE TWO DIFFERENT IN THEIR COMPOSITION.

ANS:- Full form of LPG is Liquefied petroleum gas and CNG Compressed natural gas.

LPG is obtained from crude petroleum oil. It mainly contains gaseous compounds known as isobutene and butane.

CNG is produced along with crude oil. It mainly contains methane gas.

(11)

A) WHY IS NITROGEN IMPORTANT TO ALL LIVING BEINGS?

ANS:- Nitrogen constitutes 78% of air by volume. It is mopst important element for plants and human beings for their growth.

B) WHAT IS NITROGEN FIXATION?

ANS:- Nitrogen cannot be absorbed directly by plants. It is first fixed up in the soil as nitrites and nitrates and then absorbed by the plants.  This is called nitrogen fixation.

 EXERCISE-III

(1.) WHAT IS AIR POLLUTION?

ANS:- Mixing of unwanted and harmful substances in air is called Air Pollution.

(2.) MENTION FIVE CAUSES OF AIR POLLUTION.

ANS:- The causes are-

1.Cutting of forests.

2.Erruption of volcanoes.

  1. Increase in population.
  2. Burning of FOSSIL FUELS and Fibres.

(3.) NAME TWO AIR POLLUTANTS WHICH-

a) affect our health- 1. Smoke. Dust

b) cause acid rain- Sulphur dioxide. 2. Nitrogen Dioxide.

c) cause global warming:- Methane. Carbon Dioxide.

(4.) WHAT IS MEANT BY OZONE DEPLETION?

ANS:- Ozone is present in the upper layer of atmosphere called stratosphere. It protects the earth from harmful UV rays of the sun. Some air pollutants like CFC react with ozone present in the atmosphere. These  pollutants reduce the density of the air. The  UV rays from the sun reach directly on the earth which affect human health and also increase earth’s temperature.

(5.) STATE FOUR STEPS TO BE TAKLEN TO CONTROL AIR POLLUTION.

ANS:- Steps to be taken are-

(i) Industries should be located far away from the locality.

(ii) By using smokeless source of energy like solar energy and electrical energy.

(iii) Factories and power houses should be provided with tall chimneys so that smoke and gases go hiogh up into the air.

(iv) By growing more trees and plants in big cities and towns.

(6.) NAME THREE GREENHOUSE GASES.

ANS:- CO2, METHANE, CO, NO2

Extra Questions from this Chapter:

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