Class-6 Science, Chapter-15 Air Around Us Aditional exercises with solutions in line with NCERT book / CBSE Syllabus


Chapter 15
Air Around us
=========================================================
Exercises from textbook
Additional Exercises
Tables from Textbook
Activities/Projects

Additional Exercises


Choose the correct answer:

1-    When do you notice the presence of air?
a.    Leaves of trees rustle
b.    Clothes hanging on cloth-line sway
c.    Pages of an open book flutter
d.    All the above (√)
2-    Moving air makes it possible to
a.    Fly kite
b.    Separate sand and saw dust by winnowing
c.    Both a and b (√)
d.    None of the above
3-    Our earth is surrounded by a thin layer of air called
a.    core
b.    Atmosphere (√)
c.    Ecosystem
d.    Crust
4-    The component of air which takes up nearly four-fifth of the space that air fills
a.    Nitrogen (√)
b.    Oxygen
c.    Argon
d.    Smoke and dust
5-    Plants use this gas for respiration.
a.    Carbon dioxide
b.    Agron
c.    Oxygen(√)
d.    Nitrogen
6-    Plants produce this gas in photosynthesis.
a.    Oxygen (√)
b.    Carbon dioxide
c.    Nitrogen
d.    Smoke

Science Class-7
Fill in the blanks with suitable words:
1-    Air has no colour and one can see through it.
2-    Air is a mixture of many gases.
3-    When air comes in contact with a cool surface, it condenses and drops of water appear on the cooled surface.
4-    The presence of water vapour in air is important for the water cycle in nature.
5-    Plants and animals consume oxygen for respiration and produce carbon dioxide.

State whether the following statements are True or False:
1-    Air is a mixture of many gases.                                                                             True
2-    Dust particles are always present in air.                                                               True
3-    The presence of dust particles in air varies from time to time and place to place.True
4-    Plants consume carbon dioxide for respiration.                                                    False
5-    Air is present in water and soil.                                                                             True

Match these column:
A
B
The envelop of air that surrounds the earth.
Oxygen
The gas, which supports burning and is necessary for living organisms.
Dissolved air
Aquatic animals use it in water for respiration.
Space
Air in motion is called
Atmosphere
Air occupies
Wind

Ans-
A
B
The envelop of air that surrounds the earth.
Atmosphere
The gas, which supports burning and is necessary for living organisms.
Oxygen
Aquatic animals use it in water for respiration.
Dissolved air
Air in motion is called
Wind
Air occupies
Space



Give one word for the following:
1-    Thin layer of earth around us
Ans- Atmosphere
2-    Formation of droplets of water on the cooled surface
Ans- Condensation
3-    The major part of air which does not support burning
Ans- Nitrogen
4-    The atmospheric gas that supports burning
Ans- Oxygen

Answer these questions:

Q. Why do mountaineers carry oxygen cylinders with them, while climbing high mountains?
Ans- Mountaineers carry oxygen cylinders with them, while climbing high mountains because atmospheric oxygen decreases at higher altitudes because of decrease in atmospheric pressure.

Q. Why do you see long chimneys in factories?
Ans- Long chimneys in factories take the harmful smoke and gases away from our noses and protect humans from the harmful effects of the smoke and gases.

Q. Why should you not breathe through mouth?
Ans- We should not breathe through mouth because harmful dust particles may enter your body if we do so. Our nose has fine hairs and mucus to prevent the entry of dust particles.

Q. How do the organisms that live inside the soil respire?
Ans- The organisms that live inside the soil respire using the air present in the porous soil.

Q. How will you demonstrate that plants roots respire using the air present in soil?
Ans- When the water is poured on the lump of soil, it displaces the air, which is seen in the form of bubbles. The plant roots which are inside the soil, respire in this air.

Q. Why do earthworms come out of the soil only during heavy rains?
Ans- Earthworms make holes in deep soil. This makes spaces available for air to move in and out of the soil. When it rains heavily, water fills up all the spaces occupied by the air in the soil. In this situation earthworms have to come out for respiration.

Q. Draw a diagram of windmill and write its three uses?
Ans- The wind makes the windmill rotate.

Following are uses of windmill:
1-    To draw water from tubewells
2-    To run flour mills.
3-     To generate electricity

Exercises from Textbook

1.    What is the composition of air?
Ans- Dry air is contains Nitrogen (78%), Oxygen (21%), Argon (1%), Carbon-dioxide (0.03%), water vapours, dust, smoke and some other gases.

2.    Which gas in the atmosphere is essential for respiration?
Ans- Oxygen gas in the atmosphere is essential for respiration.

3.    How will you prove that air supports burning?
Ans- To prove that air supports burning, we will perform an experiment. We will arrange the setup as shown in the figure.

The candle blows out after sometime and the water level rises in the glass.
The rise in water level indicates that the air present in glass was used up by the candle. Hence air supports burning.

4.    How will you show that air is dissolved in water?
Ans- We will perform an activity to show that air is dissolved in water.
We will slowly heat some water in a glass vessel. Well before the water begins to boil, wee observe tiny bubbles on the inner surface of vessel. These bubbles come from the air dissolved in water.


5.    Why does a lump of cotton wool shrinks in water?
Ans- A lump of cotton wool contains air in the gap between fibers. When it is immersed in water, this air is replaced by water. Cotton wool becomes heavier and shrinks.

6.    The layer of air around the earth is known as atmosphere.

7.    The component of air used by green plants to make their food is carbon dioxide.

8.    List five activities that are possible due to the presence of air.
Ans- Following are the five activities that are possible due to the presence of air:
1-    Air helps in the movement of sailing yachts
2-    Movements of gliders, parachutes and gliders is possible because of air
3-    Birds, bats and insects can fly due to the presence of air.
4-    Air helps in dispersal of seeds
5-    Air helps in dispersal of pollens of several plants.

9.    How do plants and animals help each other in the exchange of gases in the atmosphere?
Ans-

 Plants make their own food and produce oxygen. Both plants and animals use oxygen for respiration and release carbon dioxide. But plants produce more oxygen than that they consume. The balance of oxygen and carbon dioxide in the atmosphere is maintained through respiration in plants and animals and by the photosynthesis in plants.
Suggested Projects and Activities

1-    List three activities in which you can save water. For each activity describe how would you do it.
2-    Collect pictures relating to floods or drought from old magazines or news pares. Paste them in your notebook and write about the problems that people would have faced.
3-    Prepare a poster on ways of saving water and display it on your school notice board.
4-    Write a few slogans of your own on the topic ‘Save Water’.



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