States of Matter

The Gaseous State

Out of all the states of matter, the gaseous state is considered one of the simplest. A slight increase in the physical conditions of temperature or pressure can be easily observed. The study of a gas has had profound impacts on the development of various theories in nature. Let us see!

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What are Gaseous Substances?

A look at the periodic table shows us that there are 11 elements in the table that exist in the gaseous state at room temperature. These elements are Hydrogen, Helium, Nitrogen, Oxygen, Fluorine,  Chlorine, Neon, Argon, Krypton, Xenon, and Radon.

Elements that exist in gaseous state

Characteristics of a Gas

The gaseous state is the easiest to study. Any change in temperature results in evident changes in other quantities like volume and pressure. The properties can be explained easily on the basis of the Kinetic theory of gases. Therefore these facts make gases the easiest state to study. Let us see what else makes gases so special!

Highly Compressible

Gases are highly compressible. As the molecules in gaseous elements are scattered at a large distance as compared to the other two states (solid and liquid), these are highly compressible. The large intermolecular distance in the gaseous state decreases with increasing pressure. Therefore this not only decreases their volume but also brings the molecules closer to each other, thus reducing the gaps between them and making gases highly compressible.

Low Density

When compared to liquids and solids gases show very low density. As the intermolecular forces between the molecules are negligible, this state poses a very low density. But the density increases with decreasing temperature and increasing pressure.

Equal Pressure in All Directions

Have you ever seen colours fly in the air! The molecules in a gaseous element show similar behaviour. The molecules in a gaseous element scatter by forces in all direction due to the negligible force of attraction between them. Therefore the molecules exert pressure in all directions.

Source: en.wikipedia

No Shape

The shape of LPG is like the shape of the gas tank that stores it! Gases have no shape of their own. They take the shape of the container. The molecules in gaseous elements exert pressure on the walls of the container and take the shape of the container in which contains this gas.

Volume of the Container

Measuring the volume of a gas means measuring the volume of the container. Their volume is the volume of the container. Since gas scatters as soon as left loose, measuring the volume is impossible.

Mix Evenly

They mix evenly without the help of any mechanical change. The gaseous elements are more susceptible to reactions and admixtures. The huge gap between molecules gives the molecules of other elements an ease to mix with each other. This property of gases makes them highly reactive chemical elements.

Intermolecular Forces

The intermolecular force between molecules of gaseous elements is negligible. Hence these forces between the molecules in gas makes it the most compressible state of matter. The various characteristics associated with a gas also depend on the physical conditions faced by that gas. Hence in physical conditions like temperature, pressure or density may have a contradicting effect on a gases behaviour. At unchanged conditions, a gas follows an Ideal behaviour but as the conditions start changing, gases deviate from their due behaviour.

Solved Examples For You

Q: Which method do we use to separate a mixture of gases having different molecular weights?

A) Atymolysis        B) Metathesis       C) Ostwald and Walker method        D) Reverse Osmosis

Solution: A) Atmolysis is the process of separation of gases or vapours of different molecular weights by passing them through porous membranes.

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