Gases - Facts to Remember

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.

Gaseous Elements

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.

Compound Gases

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.

Useful Gases

  • 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.

Gaseous Pollutants

  • 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.

Greenhouses Gases

  1. Carbon dioxide: CO2 is the most prominent of the greenhouse gases generated through burning of fossil fuels and biological processes. Part of it is absorbed by the trees during photosynthesis.
  2. Methane (CH4): Methane is produced due to decomposition of organic matter. It is also known as Marsh Gas. Other sources include production of natural gas and coal.
  3. Water vapour: Increased warming causes more evaporation of water vapour, which traps more heat and amplifies global warming.
  4. Nitrous oxide (N2O): The gas is naturally produced from microbial activity in soils and water. Humans produce nitrous oxide from combustion of fossil fuels, biomass burning etc.
  5. Other greenhouse gases chlorofluorocarbons and hydrochlorofluorocarbons which are emitted in smaller quantities but are potently more harmful.

Gases used as Fuels

  • Natural gas is mainly methane with small quantities of ethane and propane.
  • Gobar gas is a mixture of methane, CO2 and traces of other gases.
  • Liquified Petroleum Gas (LPG) is a mixture of Butane, Propane and Ethane. (A strong smelling substance Ethyl Mercaptan or Ethanethiol is added to LPG to make it easier to detect leakages.

Quiz on Gases

Select the Correct Answer

1. LPG does not contain

2. Acid rain is caused by

3. Heaviest gas is

4. Which is not a noble gas?

5. Methane gas is

6. Percentage of oxygen in atmosphere

7. Dry ice is frozen

8. Which is also known as Laughing Gas

9. Gas used in artificial ripening of fruits

10. Also known as Marsh Gas