Air and Atmosphere ICSE Class-6th Concise Selina Chemistry

Air and Atmosphere ICSE Class-6th Concise Selina Chemistry Solutions Chapter-6. We Provide Step by Step Answer of Objective, True False , Fill in the blanks , Match the following , Short/Long Answer Type of Exercise-6 Air and Atmosphere. Visit  official Website  CISCE  for detail information about ICSE Board Class-6.


Air and Atmosphere ICSE Class-6th Concise Selina Chemistry Solutions Chapter-6


EXERCISE-I Air and Atmosphere ICSE Class-6th

Question 1.

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What is atmosphere ?
Answer:
The earth is surrounded by a thick layer of air called the atmosphere that extends upto a height of about 320 kilometres above the surface of the earth.

Question 2.

Why can’t we see air ?
Answer:
We can’t see air because it is colourless, odourless and transparent gaseous matter.

Question 3.

What is wind ?
Answer:
Fast moving air is called wind.

Question 4.

What would have happened if there would have been no atmosphere around the earth ?
Answer:
Without atmosphere life would not be possible as atmosphere protects us from harmful gases. We could not live without
air present in atmosphere. In absence of the atmopshere, the earth would get so cold at night that we would not be able to survive. No CO2 and N2 for plants without atmosphere.
P.Q. When water is heated, we see bubbles rising up. Why ?
Answer:
Water has a lot of air dissolved on it. This is what allows breathing to fishes and other aquatic beings. The solubility of gases decreases when the temperature is raised, and that is why the dissolved air bubbles out from the water.

Question 5.

Why is air called a mixture ? Give five facts in support of your answer.
Answer:
Air is a mixture because :

  1. Air has no formula, a mixture has no formula whereas compound has a formula.
  2. No energy changes are involved to form air from various gases.
  3. When air is formed out of its constituents no change in mass and no change in volume takes place.
  4. Properties of air vary from place to place and time to time. i.e. there is more CO2 in towns as compared to villages where more oxygen prevails as compared to towns.
  5. Components of air can be separated by simple physical methods.

Question 6.

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What are the main components of air ? Write down the composition of three main gases present in air by volume.
Answer:
Main components of air are :

Main components of air

Question 7.

What do you observe when

(a) Ice cold water is filled in a glass tumbler.
(b) A burning candle is covered with an inverted jar.
(c) Carbon dioxide gas is passed through lime water.
(d) A beam of light is allowed to enter in a closed dark room through a small hole.

Answer:

(a) We will observe that fine water droplets get deposited on the outer wall of the glass tumbler.
(b) The candle burn more brightly because candle gets oxygen support in burning.
(c) When CO2 gas is passed through lime water it forms calcium carbonate which is white precipitate (turbidity). This gives the milky white appearance to the solution.
(d) We will observe randomly moving dust particles in the beam of light. This confirms the presence of dust particles in the air.

Question 8.

Write the chemical name of –

(a) Lime water
(b) The white insoluble solid formed on reaction of carbon dioxide with lime water.

Answer:

(a) Calcium hydroxide Ca(OH)2
(b) Calcium carbonate – CaCO3

These droplets were present in air as moisture which got condensed on the cooler walls of glass tumbler. This shows the presence of water vapours in air.


EXERCISE-II Air and Atmosphere ICSE Class-6th

Question 1.

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Name two important processes supported by oxygen present in air.
Answer:
Two processes supported by oxygen present in air are :

  1. Combustion
  2. Respiration

Question 2.

Give two uses of the following components present in air:

(a) oxygen
(b) nitrogen
(c) carbon dioxide
(d) water vapour

Answer:

(a) Oxygen: For respiration and breathing no life is possible without oxygen.
Oxygen is the most vital component which is responsible for two most important processes,
(i) Respiration and
(ii) Combustion.
(b) Nitrogen : Present in air gets fixed up in the soil as nitrates used by plants for their growth and for the formation of protein an important nutrient for animals. It is used to make fertilizers and various nitrogenous products.

(c) Carbon dioxide : Carbon dioxide is used by plants to prepare their food by photosynthesis. Dry ice (solid carbon-dioxide) is used as a refrigerant. Carbon dioxide is used to prepare fizzy drinks like soda water.

(d) Water vapour : Water vapors present in air provide moisture for both plants and animals. It also helps in predicting climatic conditions of a particular area as its amount varies from place to place and time to time.

Question 3.

Define the following:

(a) Respiration
(b) Photosynthesis
(c) Combustion.

Answer:

(a) Respiration : Respiration is a chemical process that takes place in all living beings (slow in plants). In this process, oxygen present in inhaled air reacts with the digested food material in the body. This results in release of energy, carbon-dioxide and water.
Sugar + Oxygen → CO2 + Water + Energy.
(b) Photosynthesis : Process of producing food by green plants taking CO2 from air, water from soil by roots and in presence of sun light and chlorophyll is called photosynthesis.
(c) Combustion : Combustion also called burning “is burning of substance in oxygen of air completely producing heat and light is called combustion.”

Question 4.

What are fuels ? Give two examples of modern fuels.
Answer:
Fuels : The substances which burn in air to produce large amount of energy in the form of heat and light are called fuels.
Examples :

Question 5.

Give reasons :

(a) Aquatic animals and plants are able to survive in matter.
(b) A burning candle stops burning if covered with a glass tumbler.
(c) Mountaineers and divers carry oxygen cylinders with them.
(d) When water is heated, we see bubbles rising up.

Answer:

(a) Aquatic animals and plants use oxygen dissolved in water and survive.
(b) Oxygen is necessary for combustion when covered with a glass tumbler supply of oxygen stops.

(c) 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 (less dense) and breathing becomes difficult.
(d) These bubbles come from the air dissolved in water. The marine life uses air dissolved in water.

Question 6.

Name the processes which maintain the balance between oxygen and carbon dioxide in the air. How is it done?
Answer:
Respiration and combustion are the processes which maintain the balance between oxygen and CO2 in the air.

Respiration : 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.

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