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Gas: The simplest of all States of Matter

What is Gas?

Gas is the state of matter in which the particles are far apart, fast-moving and not organised in any particular way.

  • Gases are substances that exist in the gaseous state, which is one of the three fundamental states of matter. 
  • Gases are highly compressible and feature very large intermolecular distances.
  • The gaseous state features very small attractive forces between the gas particles, which are separated from each other by relatively greater distances when compared to liquids and solids.
  •  It is important to note that substances that exist in the gaseous state do not have any definite volume or any definite shape. 
  • They tend to occupy the entire volume of the container they are placed in.
  •  Furthermore, gases are highly compressible and are known to exert some finite pressure on the walls of their containers.

Table of Contents

Introduction to the Gaseous State

The matter is everywhere: we are made of matter, the pencils you’ve used are made of matter, the water you drink is made of matter, and the air we breathe is also a form of matter (gas). If the matter didn’t exist, nothing would. If we matter ourselves, how would we exist if matter did not? Without air, how would we breathe? This dependence of humans on air makes the gaseous state of matter, extremely important to us.

Three States of Matter

Three States of Matter – Solid, Liquid & Gas

The atmosphere is a mixture of gases such as oxygen, carbon dioxide, nitrogen, ozone, water vapour, etc. The gaseous state is the simplest of all states of matter, but only 11 gases in the periodic table behave as gases under standard temperature and pressure conditions ( STP i.e. 1 atm and 273K). These are Helium, Neon, Argon, Krypton, Xenon, Radon, Hydrogen, Nitrogen, Oxygen, Fluorine and Chlorine. These gases are called pure gases.

The difference in the intermolecular distances between the particles of solids, liquids, and gases is illustrated below. It can be observed that solids feature very tightly packed particles whereas liquids feature slightly greater intermolecular distances. Of the three states, the gaseous state can be observed to have the largest intermolecular distances. 

The primary difference between solids, liquids, and gases is that:

  • Solids (substances that exist in the solid-state) have definite shapes and occupy fixed volumes. 
  • Liquids (substances that exist in the liquid state) do not have definite shapes, but they occupy fixed volumes. They occupy the shape of their containers and are slightly compressible.
  • Gases (substances that exist in the gaseous state) do not have any definite shapes and do not occupy fixed volumes. Gaseous substances occupy the shape of their container and are highly compressible.

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Physical Characteristics of Gases

  • Gases have a lower density and are highly compressible as compared to solids and liquids.
  • They exert an equal amount of pressure in all directions.
  • The space between gas particles is a lot, and they have high kinetic energy.
  • The intermolecular forces between these gas particles are negligible.
  • These particles move at high speeds in all directions and hit each other, thus causing the gas to spread throughout the container they are kept in, evenly. This also causes them to exert pressure on the walls of the container.
  • So, gases take the volume and shape of the container.


While a real gas has negligible inter-molecular forces of attraction, an ideal gas has zero inter-molecular forces of attraction because the molecules of an ideal gas move so fast, and they are so far away from each other that they do not interact at all. There is no ideal gas that exists naturally. However, gases behave most ideally at high temperatures and low pressure conditions. The behaviour of gases is governed by certain laws.

Frequently Asked Questions – FAQs

What is meant by the gaseous state?

Gas is a state of affairs that does not have a fixed shape and a fixed size. Gasses have lower densities than other material conditions, such as solids and liquids. Among particles, there is a lot of empty space, which has a lot of kinetic energy.

Is the cloud a gas?

Water vapour and dry air are the invisible component of clouds you can’t see. Most of the atmosphere is pure air with which the transparent water vapour is combined and the very small drops of water and ice crystals are suspended in. A cloud is a gas, water, and solid mixture.

What are gasses used for?

It uses the most natural gas as an oil. Around 30 percent of the nation-wide energy consumed was derived from natural gas in 2012. It was used to generate electricity, energy, fuel, heat water, bake food, power industrial furnaces and even run air conditioners.

What gases are in the air we breathe?

In addition to oxygen, the air we breathe is made up of many other things! Only about 21 percent of air is made up of oxygen. Approximately 78 percent of the air you breathe is a gas called nitrogen. Other gases such as argon, carbon dioxide, and methane also have tiny amounts.

Why Carbon dioxide is a gas?

Since their chemical compositions are different, the reason carbon dioxide is a gas and silicon dioxide is solid. Carbon dioxide is a circular structure with two carbon-oxygen double bonds. It is a small, non-polar molecule with only weak molecular bonds. So it is a gas.

To know more about gases and Boyle’s Law, Charles’ Law, Gay Lussac’s Law, and Avagadro Law, visit our YouTube channel or download BYJU’S – The Learning App.

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