Sorting Materials Into Groups
We consider the following basic facts for understanding, to arrive at grouping materials:
- All things are made of one or more materials.
- Same things can be made from different types of materials.
- It may be man-made or naturally occurring.
- Materials occupy space.
- Materials have mass.
- Materials can be classified on the basis of physical state; as solid, liquid and gas.
Solid Liquid Gas
Solid materials have definite shape and volume. Examples: metals, wood, stones, ice, plastics, glass, etc.
Liquid has indefinite shape but definite volume. Liquids take up the shape of the solid container they are placed in. Examples: water, oil, milk etc.
Gas has indefinite shape and indefinite volume. Examples: Oxygen, nitrogen, carbon dioxide, etc.
Criteria for Sorting Materials:
- Appearance: Different materials look different from each other. The appearance depends on colour, hardness, texture and lustre.
- Hardness: Hardness is another property of materials. Some materials are very hard while some are very soft.
- Hard: Materials which are difficult to compress are called hard, e.g. diamond, stone, wood, steel, etc. Diamond is the hardest natural substance.
- Soft: Materials which can be compressed easily are called soft, e.g. chalk, cotton, rubber, etc.
Solubility or insolubility:
Soluble: Materials which easily dissolve in water are called soluble, e.g. salt, sugar, alum, etc.
Insoluble: Materials which do not dissolve in water are called insoluble, e.g. sand, chalk, iron, etc.
Water is considered as a universal solvent, so solubility in water is taken as the standard in most of the definitions; related to solubility.
The material which allows light to pass through it is called transparent material, 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.
Metals: Materials which are hard, have such luster and are good conductors of heat and electricity are called metals, e.g. iron, copper, gold, etc.
Non-metal: 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.