Gas

Gas is one of the four main phases of matter (after solid and liquid, followed by plasma).

Gas in engineering

Refer to

• • Various hydrocarbon gases used for heating, lighting, and energy transmission:
  • Natural gas
  • Liquefied Petroleum Gas (LPG), also called "cooking gas", including propane and butane
  • Synthetic gases under the general name syngas; names include coal gas, water gas, illuminating gas, wood gas, producer gas, holzgas, air gas, blue gas, manufactured gas, town gas, and hygas.
• Gasoline (petrol), especially in North America
• Gas metal arc welding

Reference to water

As energy in the form of heat is added, a solid (e.g. ice) will first melt to become a liquid (e.g. water), which will then boil or evaporate to become a gas (e.g. water vapor).

Reference to dry ice

In some circumstances, a solid (e.g. "dry ice") can directly turn into a gas: this is called sublimation. If the gas is further heated, its atoms or molecules can become (wholly or partially) ionized, turning the gas into a plasma.

Reference to fluids

Like liquids and plasmas, gases are fluids: they have the ability to flow and do not tend to return to their former configuration after deformation, although they do have viscosity. Unlike liquids, however, unconstrained gases do not occupy a fixed volume, but expand to fill whatever space they can occupy.

See also

• Gas laws
• Town Gas
• Natural Gas