Class-7 Dalal Air and Atmosphere ICSE New Simplified Chemistry Solutions

Class-7 Dalal Air and Atmosphere ICSE New Simplified Chemistry Solutions Dr Viraf J Dalal Middle School Allied Publishers Solutions. Chapter-7. We Provide Step by Step Solutions of Exercise/Lesson -7  Elements Compound and Mixtures with Objective Type Questions, Fill in the blanks and Give reason , Match the following of Dr Viraf J Dalal Middle School Chemistry Allied Publishers. Visit official Website CISCE for detail information about ICSE Board Class-7.

Class-7 Dalal Air and Atmosphere ICSE New Simplified Chemistry Solutions Chapter-7


EXERCISE-7

Question-1. 

State the meaning of the terms —

(a) Air

(b) Atmosphere

Answer-1:

(a) Air – Air is a  matter which occupies space, has mass, exerts pressure and is highly compressible

(b) Atmosphere – The envelop of air surround the earth’s layer which extends about 300 kms above earth’s surface.

Question 2.
Name the important scientists and their studies which led to the discovery of the components of air.
Answer-2:
Discoverer of components of air:

  1. John Mayow – Air has two components i.e. active and inactive
  2. Lavoiser – Active component of air is oxygen and inactive component of air is nitrogen.
  3. Other scientists discovered noble gases and carbon dioxide.

Question 3.   
Explain Lavoisier’s experiment which provided evidence to the discovery of components in air.
Answer-3:
Take mercury oxide In an apparatus and heated it on the retort, where oxygen gets collected in a bell jar.ICSE Solutions for Class 6 History and Civics - Air and Atmosphere

We observed that a red layer was formed in the heated mercury surface and the level of mercury rose by ⅕.It was then concluded that the active part of air is removed by mercury on heating was named ‘oxygen’.

Question 4.
Tabulate the various components of air, including the components with variable composition.
Answer-4:

Components of Air % by volume
Chief components
Nitrogen and Oxygen
78% – 79% 21%
Other components
Carbon dioxide Water vapour
0.02% – 0.03% variable
Rare gases
Argon, helium, radon, krypton, xenon, neon
Less than 1%
Impurities
Carbon monoxide, sulphur dioxide, oxides of nitrogen, hydrogen sulphide, dust particles.
Variable

component of air Variation place to place:

  1. At high altitudes— The amount of oxygen is less and voice versa
  2. In deep seas — The amount of oxygen is less and voice versa-
  3. In industrial areas — The amount of impurities is more

Question 5.
Compare the three main components of air e. nitrogen, oxygen and carbon dioxide with reference to their density and solubility, nature and reactivity.
Answer-5:

Nitrogen (N) Oxygen (O) Carbon Dioxide (CO2)
Density It is as heavy as air. It is slightly heavier than air. It is ½ heavier than air.
Solubility It is less soluble. It is slightly soluble. It is soluble in water.
Nature Neutral Neutral Slightly acidic
Combustibility Non-combustible Non-combustible Non-combustible
Reactivity Unreactive Very reactive Reactive

.Question 6.

 Of the total volume of air – 4/5th is nitrogen. State the utility or consequence of this ratio.

Question 7.
State how nitrogen is utilised by plants for their growth. Give a reason why nitrogen is used in flushing food packages.
Answer-7:
The consequence of having ⅘ nitrogen and ⅕ oxygen will lead to no balance of air and no photosynthesis, and earth cannot support this kind of life.

Question 8.
Oxygen of the air is utilised for ‘combustion’ and for ‘respiration’. Compare the two with a suitable examples.
Answer:

Burning of candle involves addition of oxygen to carbon & hydrogen which forms carbon dioxide , water vapour and energy in the form of heat and light.

Respiration involves inhaling oxygen to carbon & hydrogen present in food material which forms carbon dioxide , water vapor and energy in the form of heat.

Question 9.            

State the utility of carbon dioxide for manufacture of food by plants. State its role in warming the earth’s environment and in excess resulting in global warming.
Answer-9:

Green plants manufacture their own food by absorbing carbon dioxide in the air and make food in the presence of chlorophyll and sunlight called photosynthesis,.

Earth gets heated up because of infrared, visible ray & ultra violet rays. Carbon dioxide in the air allows UV rays to pass through but prevents the infrared rays from being radiated out of earth’s surface. It results in warming the earth’s environment called greenhouse effect,

Question 10.
State the utility of –
(a) Water vapour
(b) Rare or inert gases present in the air.
Answer-10:

Use of water vapour:

  1. For controlling evaporation.
  2. For determining climatic condition.
  3. For froth of plant and animal

Use of Rare or inert gases

  1.  industries – ranging from electronics
  2.  glass fibre through lighting to automotive
  3.  aerospace.

Question 11.
Give the environment effect of three polluting gases with a reason why nitrogen is not considered a polluting gas.
Answer-11:
Environment effect of three different polluting gases

  1. Sulphur dioxide –  respiratory problems
  2. Nitrogen dioxide – acid rainfall
  3. Carbon Dioxide – Global warming.

Question 12.
Describe simple experiments to show the presence of –
(a) oxygen and nitrogen component in air using a bell jar
(b) carbon dioxide in air using a test tube with outlets containing lime water.
(c) water vapour in air using a glass tumbler and ice.
Answer-12:
(a)
Oxygen and nitrogen in air:
Apparatus—
 A through, a bell jar, a cork and a crucible and a piece of white phosphorus.
ICSE Solutions for Class 6 History and Civics - Air and Atmosphere-3
Procedure –

  1. The trough is filled with water and a bell jar divided into 5 equal parts, ‘1 to 5’ is placed over it.
  2. A crucible containing white phosphorus is placed on a cork which is made to float on water.
  3. The level of the water inside and out ride are adjusted to one level.
  4. The phosphorus is then ignited by means of a heated wire.

Observation—

  1. The phosphorus burns in the active component of air [oxygen] forming – dense white fumes of phosphorus pentoxide [P2O5]. Phosphorus + Oxygen →Phosphorus pentoxide
  2. The level of the water in the bell jar rises by l/5th.

Conclusion—

  1. Oxygen— The active component of air e. 1/5th pf air is used up in burning.
  2. Nitrogen— The inactive component of air e. 4/ 5 of air is not used up in burning. Hence air contains oxygen which supports combustion and nitrogen which does not support.

(b)
Carbon dioxide in air:

Apparatus— A test tube containing lime water with two outlets ‘A’ and ‘B’.
Procedure—Air is sucked slowly from the outlet ‘B’ as shown above.
Observation— The lime water in the test tube turns milky.
Conclusion— Air which is sucked in from end ‘A’, passes through the lime water and contains carbon dioxide which turns lime water milky [This is a test for carbon dioxide gas].
ICSE Solutions for Class 6 History and Civics - Air and Atmosphere-4
(c)
Water vapour in air:
Apparatus- 
A clean dry beaker ,cube of ice
ICSE Solutions for Class 6 History and Civics - Air and Atmosphere-5
Procedure—

  1. Take a clean glass beaker dried from outside and place pieces of ice in it.
  2. Keep the beaker with the ice, aside for sometime.

Observation—

Tiny droplets of water appear on the outer surface of the beaker, which can be proved by using a dry blue cobalt chloride paper. It turns blue paper to pink in the presence of water.

Conclusion—

water vapour-condenses on the cooler surface of the beaker, proving that air contains water vapour.

Question 13.              
State four different properties of a compound and a mixture. With reference to the stated properties give reasons why air is considered a mixture and not a compound.
Answer-13:
Four Properties of compounds:

  1. They has a fixed composition.
  2. their properties is deferent from constituent component
  3. They has definite properties.
  4. They cannot be separated by physical methods.

Four Properties of mixture:

  1. Mixture has a variable composition.
  2. their properties is same as constituent component
  3. It has no definite properties.
  4. they can be separated by physical methods.

Question -14.
Explain the term ‘air pollution’, with reference to air quality. State the sources of a few main pollutants.
Answer-14:
Unwanted change in air which is harmful for man kind directly or indirectly called air pollution.

Natural sources of air pollution

a. Decay of animal and vegetable matter –

b. Volcanic eruption –

c. Lightning discharge – oxides of nitrogen

Man made sources of air pollution 

a. Burning of fuels –

b. Chemical industries –

c. Iron and steel industries –

Question- 15.
Identify the acidic oxides responsible for acid rain. State how their presence results in formation of acid rain. Give a reason why acid rain damages heritage buildings.
Answer-15:
 [SO2] and  [SO3]

Sulphur dioxide + water vapour → Sulphurous acid [H2SO3] Sulphur trioxide + water vapour→ Sulphuric acid [H2SO4]

 [NO] and  [NO2]
Nitric oxide + oxygen → nitrogen dioxide [NO2]

Nitrogen dioxide + water →  Nitric acid [HNO3]

why acid rain damages heritage buildings
Acid rain corrodes metallic surfaces & weakens building materials such as statues, marble, limestone [CaCO3] etc. It causes damage to heritage structures such as the Taj Mahal,

Question 16.
In the laboratory preparation of oxygen from hydrogen peroxide – answer the following:
(a) Draw a neat labelled diagram for the method used in the above preparation.
(b) Name the catalyst used in the preparation and state it’s function.
(c) State the word equation for the reaction involving the above preparation of oxygen.
(d) State the method of collection of the oxygen gas giving reasons.
Answer-16:
(a)
ICSE Solutions for Class 6 History and Civics - Air and Atmosphere-7
(b)

Catalyst  is manganese dioxide. .
(c)
Hydrogen peroxide → Water + oxygen
(d)
by downward displacement of water.The reasons are:
(1) Oxygen is very slightly soluble in water
(2) Oxygen is almost as heavy as air.

Question- 17.
Give word equations for the reactions of –
(a) Non-metals – (1) sulphur (2) carbon (3) phosphorus and
(b) Metals – (1) sodium (2) calcium (3) magnesium with oxygen.
Answer-17:
(a) Non-Metals

  1. Sulphur + Oxygen → sulphur dioxide
  2. Carbon + Oxygen → Carbon dioxide
  3. Phosphorus + Oxygen → Phosphorus pentoxide

(b) Metals

  1. Sodium + Oxygen → Sodium oxide
  2. Calcium + Oxygen → Calcium oxide
  3. Magnesium + Oxygen → Magnesium oxide

Question -18.                          
Distinguish between –
(a) Combustion and Respiration
(b) Combustion & Rusting with suitable word equations only ?
Answer:
(a)  Distinguish between Combustion and Respiration

Combustion Respiration
It involves oxidation of carbon and hydrogen in hydrocarbons. It involves using oxygen to oxidize food substances mainly glucose in body cells of living organisms and release carbon dioxide energy in the form of heat.
It is a rapid process at high temperatures. It is a slow process at body temperature.


(b) Distinguish between Combustion and Rusting

Combustion Rusting
It takes place in a variety of materials. It is confined only to iron.
Moisture is not required. Moisture is essential.
Oxides are formed of carbon and hydrogen Oxide of iron is formed.
Heat is evolved at a rapid rate and rises in temperature. Heat is evolved at a slow rate and causes a slight rise in temperature.

Question 19.

Give the main experimental points only to demonstrate that – (a) magnesium (b) candle-gains weight on burning.
Answer:
(a)  to show that magnesium gains weight on burning.

A small piece of magnesium is kept in a crucible with lid. It weighs 50g

Now, the crucible is heated and the lid is opened for while such that ashes do not come out.

Now when we weigh the crucible, it weighs 50.82 grams, this shows something is added to magnesium. It is the weight of oxygen which is added to magnesium

2Mg + O2 → 2MgO
Hence magnesium gains weight on burning.

(b) to show that Candle gains weight on burning
ICSE Solutions for Class 6 History and Civics - Air and Atmosphere-17

Apparatus – Unlit candle ‘A’ . U Tube ‘B’ containing anhydrous CaCl2 , Conical flask ‘C’ containing concentrated KOH solution

The whole apparatus is weighed first. Total wt = a gms.

Then, the candle ‘A’ is lit, and the products are allowed to absorb in tube ‘B’ and flask ‘C’

The candle is burnt for some time now and it is reweighed now.

There is an increase in the weight of apparatus.

It can be concluded that candle gains weight due to mass of oxygen in the air which is combined with the carbon and hydrogen of candle.

Water vapour and carbon dioxide are produced.

Question 20.               
Give reasons for the following:
(a) patients suffering from lung problems are kept in an oxygen tent.
(b) oxygens finds utility in welding & cutting of metals.
Answer:
(a) A Patients who is suffering from lung problems are kept in an oxygen tent due to artificial supply of oxygen.
(b)  because of Oxy-acetylene flame provides temperature around 3000° C and oxy-hydrogen flame provides temperature around 2800°C. hence Oxygen finds utility in welding and cutting of metals


Objective Type Questions

Class-7 Dalal Air and Atmosphere ICSE New Simplified Chemistry Solutions Chapter-7

Question-1. 

Match the statements in List I with the correct answer from List II.

List I List II
1. The constituent of air which is around 0.02% A: Nitrogen
2. The constituent of air which is inert or unreactive B: Oxygen
3. The constituent of air which is non-combustible, but supports combustion C: Sulphur dioxide
4. A pollutant in air responsible for acid rain D: Carbon dioxide
5. The main rare gas present in air E: Argon


Answer-1:

List I List II
1. The constituent of air which is around 0.02% D: Carbon dioxide
2. The constituent of air which is inert or unreactive A: Nitrogen
3. The constituent of air which is non-combustible, but supports combustion B: Oxygen
4. A pollutant in air responsible for acid rain C: Sulphur dioxide
5. The main rare gas present in air E: Argon

 

Question-2. 

Give reasons for the following:

  1. Acid rain has caused damage to heritage structures such as the Taj Mahal.
  2. In the laboratory preparation of oxygen from potassium chlorate – manganese dioxide is added to the reactant.
  3. Oxygen gas does not affect moist blue litmus paper, but carbon dioxide turns it slightly pink.
  4. Oxidation of sulphur results in a product which turns moist blue litmus red.
  5. Combustion and respiration show similarity.

 Answer-2

  1. Acid rain damages heritage buildings because it corrodes metallic surfaces and weakens building materials like statues, marbles, limestone. Taj Mahal is predominantly made of lime stone and it reacts with acids present in acid rain.
  2. Manganese dioxide alters the rate of reaction – KClO3 decomposes at a lower temperature.
  3. Oxygen is neutral and hence it does not change or react on blue litmus paper, but carbon dioxide is acidic, hence it changes blue litmus slightly pink.
  4. Oxidation of sulphur results in formation of sulphur dioxide is non-metallic acidic oxide, and hence moist blue litmus turns red.
  5. Combustion and respiration both involve oxidation of carbon and hydrogen to produce carbon dioxide and heat energy.

Question-3. 

Name the following:

  1. The product formed on oxidation of phosphorus.
  2. The acid formed when the above product of oxidation of phosphorus, reacts with water.
  3. The chemical name of rust.
  4. The pollutants which combines with water vapor to give sulphuric acid – a product of acid rain.
  5. The gas required for both combustion and rusting.

Answer-3

  1. Phosphorus pentoxide
  2. Phosphorus acid
  3. Hydrated iron (III) oxide (Fe203-xH2O)
  4. Sulphur trioxide
  5. Oxygen

Question-4.

 Select the correct answer from the choice in bracket to complete each sentence.

  1. Nitrogen of the air is utilized by plants for formation of ________.
  2. The gas evolved as a product of combustion as well as respiration is ______.
  3. A candle burs a jar of oxygen, but gets extinguished in ________.
  4. Air has variable composition and hence there is ________ oxygen at lower altitudes than at higher altitudes.
  5. Rusting is a chemical reaction which involves _______ oxidation.

Answer-4

  1. Nitrogen of the air is utilized by plants for formation of proteins.
  2. The gas evolved as a product of combustion as well as respiration is carbondioxide.
  3. A candle burns in ajar of oxygen, but gets extinguished in nitrogen.
  4. Air has variable composition and hence there is less oxygen at lower altitudes than at higher altitudes.
  5. Rusting is a chemical reaction which involves slow oxidation.

Question-5. 

Draw a neat labelled diagram for each of the following experiments.

  1. To determine the component of air used up in burning, by using phosphorus and a bell jar.
  2. To study the presence of carbon dioxide.
  3. To prove that oxygen is non-combustible, but supports combustion.
  4. To prepare oxygen in the laboratory from hydrogen peroxide and a catalyst.
  5. To demonstrate the burning of sulphur in a jar of oxygen

Answer-5

Please refer to your text book to see the figure of above question

(1)

ICSE Solutions for Class 6 History and Civics - Air and Atmosphere-20

(2)
ICSE Solutions for Class 6 History and Civics - Air and Atmosphere-21

(3)

ICSE Solutions for Class 6 History and Civics - Air and Atmosphere-22

(4)

ICSE Solutions for Class 6 History and Civics - Air and Atmosphere-23

(5)

ICSE Solutions for Class 6 History and Civics - Air and Atmosphere-24

.– : End of Air and Atmosphere Class-7 Dalal Simplified Solutions :–


Return to –  Dalal Simplified Chemistry for ICSE Class-7 Solutions

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