Gas is one of the 3 fundamental states of matter viz solid, liquid and gas. Elements or compounds which exists in such a state are known as gases. Solids have definite shape and volume, liquids have definite volume but no particular shape and gases neither have definite shape nor volume.
There are 11 gaseous elements in the periodic table, namely, Hydrogen, Nitrogen, Oxygen, Flourine, Chlorine, Helium, Neon, Argon, Krypton, Xenon and Radon. Helium, Neon, Argon, Krypton, Xenon and Radon are known as inert or noble gases because of their low reactivity. Flourine and Chlorine are 2 gases from the group of 6 elements known as halogens.
There are many compound gases meaning gases formed due the combination of 2 or more elements. The most common of them are carbon dioxide, carbon monoxide, hydrogen sulfide, sulphur dioxide, hydrogen sulfide, ammonia, methane, ethane, ethelyne, acetylene, propane, butane, nitric oxide, nitrous oxide, nitrogen dioxide.
Some random facts about gases
- The most abundant gas in earth's atmosphere is Nitrogen, which comprises about 78% of the atmosphere.
- The percentage of oxygen in earth's atmosphere is about 21%
- The lightest gas is Hydrogen.
- The heaviest gas is Radon.
- Ozone (O3) is an allotrope of oxygen. Ozone layer in the stratosphere absorbs most of sun's ultraviolet radiation protecting the inhabitants from its harmful effects.
- Acetylene is used in gas welding and also artificial ripening of fruits.
- Argon is used in incandescent electric bulbs
- Nitrous Oxide, also known as Laughing Gas, is used as an anaesthetic in dental surgery.
- Helium is mixed with oxygen meant for breathing to prevent a state of intoxication caused by pure oxygen.
- Mercury vapour is used in flourescent lamps (tube lights).
- Freon (Diflouro Dichloro Methane) is a gas used in refrigeration.
- Ammonia (NH3) gas is used in tear gas shells used commonly to disperse unruly crowds
- Carbon dioxide in its solid form is known as Dry Ice. Dry ice is used for refrigeration and in fire extinguishers.
- Carbon monoxide: A major air pollutant emanating from burning of fossil fuels. The percentage presence of which is checked in vehicle pollution test.
- Nitric oxide and Nitrogen dioxide: Combinedly known as nitrogen oxides, they are released to the air from the exhaust of motor vehicles, the burning of coal, oil, or natural gas. Nitrogen oxide is responsible for the formation of brown air in traffic congested cities.
- Sulphur dioxide: Emitted from coal fired plants and also from processes such as petroleum refining etc. It is one of the two gases responsible for acid rain, the other being nitrogen dioxide.
- Hydrogen Sulfide (H2S): It is produced from microbial breakdown of organic matter in the absence of oxygen such as in swamps and sewers. It is characterised by its strong smell of rotten eggs.