Q39. Write four properties of the air.
Properties of the air
Air is invisible.
Air occupies space.
Air is transparent.
Air has no color.
Q40. During an incident of fire, one is advised to wrap a woolen
blanket over a burning object. Explain why?
During an incident of fire, one is advised to wrap a woolen blanket over a
burning object because air gaps in woolen blanket act as an insulating medium
which cuts the supply of oxygen to the object that is burning thereby prevent
it from further burning.
Q41. How will you show that air is dissolved in water?
Take some water in a glass vessel or beaker. Heat it slowly on a tripod stand. Well
before the water begins to boil, we see tiny bubbles at the inner surface of
These bubbles come from the air dissolved in water. This proves that air is
dissolved in water.
Q42. How do organisms living under the soil get air for
The organisms which are living under the soil such as in the roots of a plant
respire by taking oxygen present in the soil. Some organisms make deep burrows
and holes in the soil through which the air reaches them for respiration.
Q43. Why do living things need air to survive?
Living things cannot survive without air. We breathe in oxygen and breathe out
Carbon Dioxide. Through a process called photosynthesis,
plants extract carbon dioxide from the air and use it to produce energy. They
release oxygen in the air in this process. Thus air is important for all living
Q44. What is wind energy? Write its two advantages.
Wind energy is a form of renewable energy produced through machines that uses
movement of wind as their power source.
Wind is a free and infinite resource.
Wind is a clean energy source.
Q45. Prove that 'Air
contains dust and smoke’.
Close all the doors and windows with curtains pulled down to make the room
dark. Now, open the door or a window facing the sun, just a little, in such a
way that it allows sunlight to enter the room only through a slit. We see some
tiny shining particles moving in the beam of sunlight. This shows that air also
contains dust particles.
Q46. What are the major constituents of air and their
The major constituents of air and their percentages are:
dioxide - 0.04%
also contains other gases, water vapor and dust particle.
Q47. What are the activities which can be possible only in the
presence of air?
Activities which can be possible only in the presence of air are:
Generation of electricity by windmills
Sailing of ship
Q48. How balance of oxygen and carbon dioxide in the atmosphere
During photosynthesis plant uses carbon dioxide and releases oxygen. Plants
also consume oxygen for respiration, but they produce more of it than they consume.
Oxygen in air is used by living organism present in air, water or soil during
respiration. This shows the interdependence of plants and animals and thus the
balance of oxygen and carbon dioxide in the atmosphere is maintained.
Q49. Draw a diagram showing composition of air in atmosphere.
Q50. How do you prove air occupies space?
following activity proves that air occupies space.
an empty glass bottle. Turn it, upside down. Now, dip the open mouth of the
bottle into the bucket filled with water. Water does not enter the bottle. Now
tilt the bottle slightly. Now water enters the bottle and we see bubbles coming
out of the bottle.
bottle was not empty at all. In fact, it was filled completely with air even
when we turned it upside down. That is why water does not enter the bottle when
it is in an inverted position, as there was no space for air to escape. When
the bottle was tilted, the air was able to come out in the form of bubbles, and
water filled up the empty space that the air has occupied.
activity shows that air occupies space.
Q51. How will you demonstrate that air mainly contains oxygen
We can show that air mainly contains oxygen and nitrogen from the following
two small candles of the same size in the middle of two shallow containers.
Now, fill the containers with some water. Light the candles and then cover each
one of them with an inverted glass. When most of this oxygen is used up by the
burning candle, it can no longer burn and blows out. Also, some of the space
occupied by the oxygen inside the glass becomes empty and the water rises up to
fill or occupy this space.
major part of air is still present in the glass bottle even after the candle
blew out. This indicates the presence of some component in the air, which does
not support burning. The major part of air (which does not support burning
candle) is nitrogen. It takes up nearly four-fifth of the space that air fills.