Air and Air Pollution Questions in English

(N/A) $(i)$ In the atmosphere,oxygen is found in the elemental form to the extent of $21 \%$.
$(ii)$ In combined form,it occurs as $CO_{2}$ both in the earth's crust as well as in the air.
$(iii)$ In the crust,it is found as the oxides of most metals and silicon,and also as carbonate,sulphate,nitrate,and other minerals.
$(iv)$ It is also an essential component of most biological molecules like carbohydrates,proteins,nucleic acids,and fats (or lipids).

(B) Greenhouse gases are gases in the Earth's atmosphere that trap heat. They allow sunlight to pass through the atmosphere but prevent the heat that the sunlight brings from leaving the atmosphere.
Common greenhouse gases include carbon dioxide $(CO_{2})$,methane $(CH_{4})$,nitrous oxide $(N_{2}O)$,and water vapor.
Oxygen $(O_{2})$ is not a greenhouse gas because it does not absorb infrared radiation emitted from the Earth's surface.
Therefore,the correct option is $B$.

(B) The Earth's atmosphere is primarily heated through a process involving solar radiation and terrestrial radiation.
$1$. The sun emits short-wave radiation that passes through the atmosphere and reaches the Earth's surface.
$2$. The Earth's surface (land and water bodies) absorbs this energy and gets heated.
$3$. The heated surface then re-radiates this energy back into the atmosphere in the form of long-wave infrared radiation.
$4$. Greenhouse gases in the atmosphere trap this re-radiated heat,thereby warming the atmosphere.
Therefore,the atmosphere is mainly heated by the energy re-radiated by land and water.

(C) The atmosphere acts as a blanket for the Earth. It traps heat during the day through the greenhouse effect and prevents it from escaping rapidly into space at night.
If there were no atmosphere,the Earth would receive intense solar radiation during the day,causing the temperature to rise significantly.
Conversely,at night,all the heat would radiate back into space,causing the temperature to drop drastically.
Therefore,the temperature would increase during the day and decrease during the night.

(B) Carbon dioxide $(CO_2)$ is a greenhouse gas. An increase in its concentration leads to the trapping of more heat,resulting in global warming ($A$ and $C$).
$CO_2$ is a raw material for photosynthesis,so an increase in its concentration can enhance the rate of photosynthesis in many plants $(D)$.
However,an increase in $CO_2$ does not directly cause an abundance of desert plants. Desert plants are adapted to arid conditions,and their distribution is primarily limited by water availability,not by the concentration of $CO_2$ in the atmosphere. Therefore,option $B$ is the correct answer.

(B) During cold weather,the temperature is low,which causes water vapor in the air to condense around dust particles or smoke particles (such as unburnt carbon particles or hydrocarbons) released from combustion processes.
This mixture of smoke and fog is known as smog.
The suspended particles scatter light,which significantly reduces visibility in the atmosphere.

(D) The air we breathe contains approximately $78\%$ nitrogen and $21\%$ oxygen.
While oxygen is essential for cellular respiration and is absorbed into the blood through the alveoli in the lungs,nitrogen is an inert gas in the context of human metabolism.
Because nitrogen does not participate in any metabolic reactions within the body,it is not absorbed by the blood or cells.
Therefore,the nitrogen that enters the lungs during inhalation simply remains in the air passages and is expelled from the body along with $CO_2$ during the process of exhalation.

(A) The term $Smog$ is derived from the combination of two words: $Smoke$ and $Fog$.
It is a type of intense air pollution that reduces visibility.
$Smoke$ consists of particulate matter,while $Fog$ consists of water droplets suspended in the air.
When these two combine,especially in urban areas with high levels of pollutants,they form $Smog$.

(TRUE) The statement is True.
While oxygen is essential for aerobic respiration in most living organisms,there are specific groups of microorganisms known as obligate anaerobes (such as certain bacteria like $Clostridium$ species) for which elemental oxygen is toxic and can be lethal.

(TRUE) True.
Carbon dioxide $(CO_2)$ is a primary greenhouse gas that traps heat in the Earth's atmosphere,contributing to the greenhouse effect and global warming.

(B) The statement is False.
Explanation:
$1$. Photosynthesis is a process where plants use $CO_2$ and water to produce glucose and oxygen,thereby reducing the amount of $CO_2$ in the atmosphere.
$2$. The process described in the statement,where fuels are burnt to provide energy,is known as combustion or respiration,not photosynthesis.
$3$. Combustion of fossil fuels releases $CO_2$ into the atmosphere,which is the opposite of the function of photosynthesis.

(A) The statement is True.
The uneven heating of the Earth's surface by solar radiation creates temperature differences in the atmosphere.
Warm air is less dense and rises,creating low-pressure areas,while cooler air is denser and sinks,creating high-pressure areas.
Air moves from high-pressure regions to low-pressure regions to balance these differences,resulting in wind and various atmospheric phenomena such as storms,rainfall,and seasonal changes.

(FALSE) False. The heating of air causes water to evaporate,turning liquid water into water vapour. Condensation occurs when air cools down,causing water vapour to turn back into tiny liquid water droplets.