Nitrogen and Other Gases
Nitrogen occurs in both free state and in combined state in nature. In free state, nitrogen constitutes about 78% of the air. In combined state, it occurs as a constituent of minerals such as nitre. Nitrogen is made up of a molecule consisting of two atoms of nitrogen. It is a colourless, odourless and tasteless gas. Nitrogen is neither combustible nor a supporter of combustion. It is highly stable and inert gas. Metals on burning in presence of nitrogen form metal nitrides. Nitrogen is important to plants and animals. Plants cannot use free nitrogen. Therefore, it is essential to convert free atmospheric nitrogen into compounds so that plants and animals can use easily. Transformation of atmospheric nitrogen into the form that plants can readily use, is termed as nitrogen fixation. The nitrogen fixation can be biological or non- biological. The cyclic process of fixing atmospheric nitrogen into essential nitrogenous compounds, used by plants, animals and humans and its return to atmosphere constitutes nitrogen cycle. Nitrogen has many uses like it is used in food packaging to keep the food fresh for a long time. Nitrogen is used in the manufacture of fertilisers. Rare gases are also called inert gases or noble gases because they are highly stable and unreactive. E.g., helium, neon, argon etc. There are many uses of various rare gases. Deep sea divers use a helium oxygen mixture for breathing. Argon is filled in electric bulbs to prevent the reaction of air with the metal of bulb filament on being heated up. Radon is used in the treatment of cancer because it is radioactive in nature. Along with gases certain amount of water vapours are always present in air. Humidity is the amount of water vapour present in the air. The presence of water vapours in the air is maintained by water cycle. The process by which water continually changes its form and circulates between oceans, atmosphere and land is termed as water cycle. Various phases of water cycle are evaporation, condensation, precipitation and collection. Precipitation occurs when evaporated water condenses and falls back to the earth in the form of rain, hail, sleet or snow.
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