SORTING MATERIALS INTO GROUPS:
• 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 many criteria.
• Materials can be classified on the basis of physical state; as solid, liquid and gas.
Solid: Solid Has Definite Shape And Definite Volume.
Examples: Stones, Wood, Plastic, Common Salt, Steel, Ice, Glass, Etc.
Liquid: Liquid Has Indefinite Shape But Definite Volume.
Examples: Water, Milk, Oil, Etc.
Gas: Gas Has Indefinite Shape And Indefinite Volume.
Examples: Oxygen, Nitrogen, Carbon Dioxide, Etc.
Other 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- Material 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: Material which easily dissolves in water is called soluble, e.g. salt, sugar, alum, etc.
Insoluble: Material which does not dissolve in water is called insoluble, e.g. sand, chalk, iron, etc.
Since water is considered as universal solvent, so solubility in water is taken as standard in most of the definitions; related to solubility.
Transparency: The material which allows light to pass through it is called transparent, e.g. acrylic sheet, glass, water, air, etc.
Opaque: The material which does not allow light to pass through it is called opaque, e.g. wood, iron, asbestos, etc.
Translucent: 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.
Properties of Materials:
Objects are categorised on the basis of their shapes, the materials they are made up of, and the properties of these materials.
Most metals have this property. Other materials like wood or plastic, are non-lustrous.
Metals like iron may react with the moisture in the air, which makes them lose their lustre and look dull.