Class 6 Science

Sorting Materials into Groups

Sorting materials into groups on different criteria make our life easier. We can find an object in no time if objects are kept in proper group.

Solid Liquid & Gas

solid liquid and gas

Fig:States of Matter


Solid has definite shape and definite volume. Examples: Stones, wood, plastic, common salt, steel, ice, glass, etc.


Liquid has indefinite shape but definite volume. Examples: Water, milk, oil, etc.


Gas has indefinite shape and indefinite volume. Examples: Oxygen, nitrogen, carbon dioxide, etc.

Other Criteria For Sorting Materials:


Different materials look different from each other. The appearance depends on colour, hardness, texture, and lustre.


Hardness is another property of materials. Some materials are very hard while some are very soft.

  1. Hard: Material which are difficult to compress are called hard, e.g. diamond, stone, wood, steel, etc. Diamond is the hardest natural substance.
  2. Soft: Materials which can be compressed easily are called soft, e.g. chalk, cotton, rubber, etc.

Solubility or insolubility

  1. Soluble: Material which easily dissolves in water is called soluble, e.g. salt, sugar, alum, etc.
  2. Insoluble: Material which does not dissolve in water is called insoluble, e.g. sand, chalk, iron, etc.

Note: Since water is considered as universal solvent, so solubility in water is taken as standard in most of the definitions; related to solubility.


transparent translucent opaque



The material which allows light to pass through it is called transparent, e.g. acrylic sheet, glass, water, air, etc.


The material which does not allow light to pass through it is called opaque, e.g. wood, iron, asbestos, etc.


The material through which light can pass partially is called translucent, e.g. butter paper, thin curtain, etc.


Materials which are hard, have such luster and are good conductors of heat and electricity are called metals, e.g. iron, copper, gold, etc.


Materials which are brittle, which don’t have luster and are bad conductors of heat and electricity are called non-metals, e.g. coal, chalk, rubber, soil, etc.