Which of the following processes need oxygen?
Oxygen is necessary for combustion, respiration and oxidation.
Which of the following statements is true regarding the earth's atmosphere?
The density of air decreases with an increase in altitude.
When we heat water, we find bubbles coming from it. This shows that
Water contains dissolved air. Note: Sol ability of gases decreases on increase of temperature.
Which of the following plays a very important role in the oxygen cycle?
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.
Mountaineers carry oxygen cylinders with them because
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.
Which of the following can show the direction of the wind?
A wind vane is used to find the direction of the wind.
Which of the constituents of air on increasing, causes global warming?
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 air is called
The percentage of water vapour present in the air is called humidity.
Plants require nitrogen for
Plants require nitrogen for their growth and for the formation of proteins.
Which of the following gases cause the harmful greenhouse effect?
High levels of carbon dioxide in the atmosphere cause the harmful greenhouse effect.
The percentage of nitrogen in air is
The percentage of nitrogen in the air is 78%.
Breathing of air through our mouth is not hygienic because
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.
Which of the following enables us to drink a liquid through a straw?
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.
The humidity of a place
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.
Lime water turns milky when exposed to air. This shows that air contains
Carbon dioxide in air turns lime water milky.
The correct ascending order of gases as per their composition in air is
The correct ascending order of gases as per their composition in air is hydrogen and other gases (1%), oxygen (21%) and nitrogen (78%).
Air is useful for
Air is useful in many ways, like in the generation of electricity, the dispersal of seeds and in bird's flight.
Which of the following is combustible?
Hydrogen is a combustible gas. It burns with a pale blue flame.
Which of the following statements is true regarding the properties of air?
Air is transparent, a bad conductor of electricity and heat and also its composition varies from place to place.
Match the following terms in Column-l with those in Column-II correctly.
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