States of Matter


Matter exists in three different states solid, liquid and gas. These states of matter arise due to the variation in the extent of intermolecular forces and intermolecular space.

The Solid State

In this state of matter, the substances have definite mass, volume, and shape. Wood, table, pen, and book are examples of solid states of matter. The intermolecular space in between the constituent particles of solid state is small, but the intermolecular forces are strong. Thus, the constituent particles such as atoms, molecules or ions cannot move but can only oscillate about their mean position. This is the reason why solids are incompressible and rigid i.e., have definite shape and size. Because of the presence of strong intermolecular forces, these are highly dense and generally have high melting point.

Classification of Solids

These can be classified into two groups

  1. Crystalline Solids. They consist of a large number of crystals. In a crystal, the arrangement of particles is regular e.g., sodium chloride, diamond, quartz (crystalline), graphite, etc.
  2. Amorphous Solids They consist of particles of irregular shape. The arrangement of particles in amorphous solid is disordered, e.g., glass, rubber, and plastics, amorphous solids are also called pseudo solids or supercooled liquids.

The Liquid State

In this state, the substances have no fixed shape but have a fixed volume. They take up the shape of the container in which they are kept, e.g., water, oil, milk, etc. The upper surface of the liquid is always planar whatever be the shape of the container. Liquids flow and change their shape, so they are not rigid and are called fluids ( the substance which can flow).

In liquids, intermolecular forces are no longer strong enough to hold the particles together, that’s why they are less densely compressed. However, the forces are still sufficient so that particles cannot escape each other’s environment, so they have sufficient mobility and fixed volume.

The Gaseous State

In this state, matter has no fixed shape and volume. They only occupy the shape and size of the container in which they are kept e.g., air, H2, O2, N2, etc. In the gaseous state, the intermolecular forces are very weak, so the intermolecular spaces between the molecules are very large. This is the reason that gases are highly compressible as compared to solids and liquids. Gases also flow in the container as compared to solids and liquids. Gases also flow in the container in which they are kept so they are also called fluids.

Further, gases expand more as compared to liquids and solids when heated due to the weaker intermolecular forces as compared to liquids and solids

Plasma State

It consists of super energetic and super excited particles. These particles are in the form of ionized gases. The fluorescent tube (filled with helium or any other gas) and neon sign bulbs (filled with neon) consist of plasma. The sun and the stars glow because of the presence of plasma in them. The plasma is created in stars because of very high temperature.

Bose-Einstein Condensate (BEC)

This state of matter is named after the name of scientists Satyends Nath bose (India) and Albert Einstein. The BEC is formed by cooling a gas of extremely low density, about one hundred thousandths the density of normal air, to super low temperatures. In 2001, Eric A Cornell, Wolfgang Ketterle and Carl E Wieman of USA received nobel prize in Physics of achieving (Bose-Einstein Condensate)


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