Question

NCERT VI Social Sciences

Answer the following questions.

(a) Name the constituents of air and give their proportion in air.
(b) Of what use is carbon dioxide to plants?
(c) What is meant by nitrogen fixation? How does it happen?
(d) Which measures are necessary for arresting pollution?
(e) What ill-effects of pollution are being seen?
(f) What function does an observatory perform?

Answer 1

(i) Nitrogen-78.08% Oxygen-20.95% Argon-0.93% Carbon dioxide-0.038% Krypton-0.0001% Helium-0.0005% Hydrogen-0.00005% Neon-0.0018% Xenon-0.000009% (ii)Carbon dioxide is used by the plants to make their food by the process of photosynthesis whereby the green plants make their own food with the help of water, sunlight and carbon dioxide and give out oxygen which is used for the process of respiration by animals. (iii)Nitrogen fixation is a chemical process in which atmospheric nitrogen is assimilated into organic compounds in living organisms and in nitrogen cycle. (iv)Plants designed 10 years or before or by lowly equipped designs are sure cases for detailed study. For prevention generous use of scrubbers & filters will be necessary. It is said that a routine check will reduce 10%, a minor modification will reduce 15-20% and a thorough overhauling of the system will reduce more than 30% of power consumption and pollution creation. (v)Acidification Eutrophication Ground-level ozone Particulate matter (vi)An observatory is a location used for observing terrestrial or celestial events. Astronomy, climatology/meteorology, geology, oceanography and volcanology are examples of disciplines for which observatories have been constructed.

Answer 2

(a) By volume, dry air contains 78.09% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide, and small amounts of other gases. Air also contains a variable amount of water vapor, on average around 1% at sea level, and 0.4% over the entire atmosphere.

(b) In a process called “photosynthesis,” plants use the energy in sunlight to convert CO2 and water to sugar and oxygen. The plants use the sugar for food—food that we use, too, when we eat plants or animals that have eaten plants — and they release the oxygen into the atmosphere.

(c) The chemical processes by which atmospheric nitrogen is assimilated into organic compounds, especially by certain microorganisms as part of the nitrogen cycle.Nitrogen fixation is a process by which nitrogen in the Earth's atmosphere is converted into ammonia (NH3) or related nitrogenous compounds. ... It also occurs naturally in the air by means of NOx production by lightning.

(d) The important point is to use less plastic and write on both sides of paper. Use old newspaper to cover the books and notebooks.

(e) Human Health: The decrease in quality of air leads to several respiratory problems including asthma or lung cancer. Chest pain, congestion, throat inflammation, cardiovascular disease, respiratory disease are some of diseases that can be causes by air pollution.

(f) An observatory is a location used for observing terrestrial or celestial events. Astronomy, climatology/meteorology, geophysical, oceanography and volcanology are examples of disciplines for which observatories have been constructed.

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