Gas is a state of matter with no fixed shape and no fixed volume. The other states of matter are solid, liquid, and plasma. Gases have varied properties from other states of matter. A pure gas may be made up of individual atoms(like Nitrogen, Oxygen, etc.) or a mixture of different atoms(like Carbon Dioxide, Sulfur Dioxide, etc.). Common examples of gases are Oxygen, Carbon Dioxide, Ammonia gas, Air(which is a mixture of gases), etc. Gases can be classified into various types based on the number of atoms, reactivity, compression process, origin, toxicity, etc. In this article, we discuss the 12 types of gases.
Types of Gas
- Monoatomic gases
- Polyatomic gases
- Elemental gas
- Gas containing different elements
- Inert gas
- Toxic gas
- Natural gas
- Biogas
- LPG
- CNG
- Real gas
- Ideal gas
Let us discuss each type of gas in detail:
Monoatomic gases
Monatomic gases as the name suggests are a combination of two words “mono” and “atomic” meaning a gas consisting of a single atom. The thermodynamic behavior of a monatomic gas is different from a polyatomic gas as monoatomic gases do not have rotational and vibrational power components at ordinary temperatures.
Examples of monoatomic gases:
- Helium
- Neon
- Argon
- Krypton
- Xenon
- Radon
- Oganesson
Polyatomic gases
Polyatomic gases as the name suggest mean gases that have two or more atoms. Examples include Hydrogen(H2), Oxygen(O2), Nitrogen(N2), Sulfur Trioxide(SO3), Carbon Dioxide(CO2), etc. These gases are more reactive than monoatomic gases which are mostly inert. Polyatomic gases can be further classified into different types based on the number of atoms like Diatomic, Triatomic, Tetratomic, etc.
Examples of diatomic gases:
- Hydrogen (H2)
- Nitrogen (N2)
- Oxygen (O2)
- Fluorine (F2)
- Chlorine (Cl2)
- Iodine (I2)
Examples of triatomic gases
- Ozone (O3)
- Carbon Dioxide (CO2)
- Water vapor or steam (H2O)
Examples of tetra atomic gases :
- Sulfur trioxide (SO3)
- Ammonia gas (NH3)
Inert gases
An inert gas is a gas that does not undergo chemical reactions that easily, in other words, it is an extremely stable gas. Most of the inert gases are nobles gases from Group 18 of the periodic table(A chart of all the elements). Inert gases are used generally to avoid unwanted chemical reactions. They are colorless, odorless, tasteless, and non-flammable gases. But given the term inert gas, they are not always inert, they can be made to react under special conditions.
Examples of inert gas
- Helium
- Neon
- Argon
- Krypton
- Xenon
- Radon
Toxic gases
Toxic gases as the name suggests are gases that are toxic to human beings. These gases must be stored under continuous ventilation either in a fume hood or ventilated gas cabinet. The toxicity of the gases can be assessed by looking at the LC50 (median lethal dose) value. These gases are harmful to all living beings in general. Inhalation of toxic gases can affect the central nervous system, cause severe illness, or even death. Toxic gases must be labeled properly and handled at proper concentration and with proper care.
Examples of toxic gases
- Ammonia
- Arsine
- Boron Trichloride
- Boron Trifluoride
- 1,3-Butadiene
- Carbon Monoxide
- Chlorine gas
- Hydrogen Fluoride
- Sulfur Dioxide
- Vinyl Chloride
Ideal gas
An ideal gas is a type of gas that follows the ideal gas equation. An ideal gas can be described in terms of three parameters: the volume that it occupies, the pressure(Force per unit area) that it exerts, and its temperature. The biggest advantage that we get by treating real gases as an ideal gas is that we have a simple equation of state with only a single constant.
Real gas
A real gas is a non-ideal gas meaning it does not follow the ideal gas law. The term ‘real gas’ is usually used to comprehend the behavior of the gases with respect to compressibility effects, variable specific heat capacity, non-equilibrium thermodynamic effects, van der Waals forces, etc. For most cases, the ideal gas approximation may work to some extent.
Elemental gas
Certain elements are stable as gases like Nitrogen(N2), Oxygen(O2), and Ozone Ozone, (O3). With a change in temperature or pressure, the stability of the gases may vary.
Gas containing different elements
Most gases contain atoms from different elements like Carbon Dioxide (CO2), Water vapor(H2O), Sulfur Oxides(SOx), Nitrogen Oxides(NOx), etc.
Natural gas
Natural gas also known as fossil fuels is a mixture of hydrocarbon gases (consisting mostly of alkanes and methane with other minor percentages of gases) that is formed beneath the Earth’s surface. It is colorless and odorless and is a highly flammable gas. It is used widely in the manufacture of plastics and is necessary for a wide array of other chemical products, including fertilizers and dyes.
Biogas
Biogas is a renewable fuel produced by the breakdown of organic matter(any matter containing hydrocarbons) such as human or animal waste. It is a mixture of gases, primarily consisting of methane, carbon dioxide, and hydrogen sulfide. It can be used as a vehicle fuel, for cooking, and for electricity generation. It is a renewable power source.
LPG
The full form of LPG is Liquefied petroleum gas. It is a flammable mixture of hydrocarbon gases and is the liquefied state of petroleum gases. LPG is used as fuel gas for cooking purposes and as fuel for vehicles. It is also nowadays widely used as an aerosol propellant to replace the harmful chlorofluorocarbons to reduce the damage to the ozone layer.
CNG
The full form of CNG is Compressed natural gas (CNG). It is mainly composed of methane (CH4), compressed to less than 1% of the volume. It is an eco-friendly alternative to gasoline and the CNG engines of vehicles functions similarly to gasoline engine. It is stored and distributed in complex containers usually in cylindrical or spherical shapes. CNG is non-toxic and does not contaminate groundwater, and hence is considered a safer fuel alternative.
How is a real gas different from an ideal gas?
A real gas is a gas that we see around us. All gases in nature are typically non-ideal, that is why we have the name real gases. An ideal gas is an imaginary theory to define how gases behave in an ideal scenario. An ideal gas has no definite volume but in reality, gases do have volumes. Real gas particles undergo non-elastic collisions, but in ideal gases the collision of particles is elastic.
Is vapor a type of gas?
The terms vapor and gas might be confusing for anyone. In physics, vapor can be defined as a substance that is in the gas phase at a specific temperature but is normally in a different state of matter. For example, water is generally in a liquid state, but when at a temperature of 273 K, it undergoes a state of temperature into a gaseous state and we call it water vapor.
CNG and LPG are types of gases?
CNG is a gas and it remains in the gaseous state even while it is compressed. LPG on the other hand is liquified at high pressure but is gaseous at normal pressure and temperature.
