Classification of Matter

Matter can be classified into different categories depending upon their physical or chemical nature.

Matter exists in three states - Solids, Liquids and Gases

A solid

• has a definite characteristic shape

• tends to resist deformation of its shape

• is relatively non compressible

For example, diamond

Solids can be classified as:

• Crystalline

• Amorphous

In a crystalline substance the solid is characterised by a very definite, well-defined external geometric shape such as cube, octahedron or tetrahedron.

Internally, particles are orderly arranged in a three-dimensional pattern.

For example: common salt and copper sulphate

Amorphous (without structure) solids do not exhibit clear-cut external geometrical shapes. Their internal particle arrangements are less regular and do not have defined melting point with a tendency to deform more easily.

For example: Glass and plastic. Glass is so presented/cited for it does not resist deformation very well. It softens rather than melts when heated and sags and flows on heating over a long period of time.

A liquid

• has a definite volume

• no characteristic shape

• takes the shape of the container

• is fluid - is able to flow and change shape without separation

• is essentially non compressible

For example: water and milk

Liquids take shape of their container

A gas

• has no definite volume or shape

• is fluid

• is very compressible. It takes the volume and shape of the vessel in which it is kept.

For example: Hydrogen and carbon dioxide

All the three states of matter are inter-convertible.

For example: water

When water is cooled to 0^oC, it transforms into ice (solid). On heating, at 100^oC, it begins to boil and gets converted into vapor (gas). On cooling, water vapor gradually converts back into water (liquid).

Fourth and fifth states of matter (Additional information)

The fourth state called plasma refers to the super heated gaseous state. This is a mixture of electrons and positively charged ions with unusual properties. It is found at extremely high temperatures such as interiors of the sun or stars. Astronomers reveal that 99% of all matter in the universe is present in the plasma state.

The fifth state refers to super cooled solid. Atoms lose their separate identity and get condensed. They behave like a single super atom. This study is based upon Bose-Einstein condensation concept developed in 1924.