Olympiad Test: Air Around Us - Class 6 MCQ

Oxygen is necessary for combustion, respiration and oxidation.

The density of air decreases with an increase in altitude.

Water contains dissolved air. Note: Sol ability of gases decreases on increase of temperature.

Plants play an important role in the oxygen cycle, as they release oxygen during the process of photosynthesis. Thus, they help in balancing the oxygen content in the atmosphere.

The density of air decreases with altitude, so the oxygen needed for breathing also decreases and becomes difficult to breathe. Hence, mountaineers carry oxygen cylinders.

A wind vane is used to find the direction of the wind.
An anemometer is an instrument that measures wind speed and wind pressure
A barometer is a tool used to measure atmospheric pressure,

Carbon dioxide traps the reflected rays of the sun that fall on the earth's surface. This results in the increase of the earth's temperature, which is referred as global warming.

The percentage of water vapour present in the air is called humidity.

Plants require nitrogen for their growth and for the formation of proteins.

High levels of carbon dioxide in the atmosphere cause the harmful greenhouse effect.

The percentage of nitrogen in the air is 78%.

If we breathe air through our mouth, the dust particles present in the air may enter the lungs and cause harm. But if the nose is used for breathing, the hair present in the nose filters the air and prevents the dust particles from entering the lungs.

When a straw is used for drinking, air is expelled out from the straw due to which there is a decrease in the air pressure inside the straw. Therefore, the liquid in the container enters the straw, rises up and comes out from the straw. So, we are able to drink the juice/liquid. When we stop using the straw the process stops.

Humidity varies from time to time and from place to place. It is not fixed because it depends on the temperature of that place at that particular time.

Carbon dioxide in air turns lime water milky.

The correct ascending order of gases as per their composition in air is: hydrogen < oxygen < nitrogen. 

Air is useful in many ways, like in the generation of electricity, the dispersal of seeds and in bird's flight.

Hydrogen is a combustible gas. It burns with a pale blue flame.

Air is transparent, a bad conductor of electricity and heat and also its composition varies from place to place.

The correct combination is a - 4, b - 3, c - 2, d - 1
(i) Aquatic animals-Dissolved oxygen
(ii) Mountaineers-Oxygen cylinders
(iii) Factories-Soot and dust
(iv) Wind-Sail boat