Sorting materials into group :- All objects around us are made of one or more materials. These materials may be glass, metal, plastics, wood, cotton, paper, mud or soil.
Some materials are shiny in appearance while others are not. Some are rough, some smooth. Similarly, some materials are hard, whereas some others are soft.
Properties of materials :-
- Appearance:- Materials usually look different from each other. Such as wood looks very different from iron and iron appears different from copper or aluminium.
- Lustre:- Materials that have lustre are usually metals. Iron, copper, aluminium and gold are examples of metals.
- Hardness:- When you press different materials with your hands, some of them may be hard to compress while others can be easily compressed. Materials which can be compressed or scratched easily are called soft while some other materials which are difficult to compress are called hard. For example:– cotton or sponge is soft while iron is hard.
- Soluble:-Those substances which have completely disappeared or dissolved in water. We say that these substances are soluble in water.
- Insoluble:- Those substances which do not mix with water and do not disappear even after we stir for a long time. These substances are insoluble in water.
- Objects may float or sink in water:- For example:- Leaves float on water but stones sink in water.
- Transparency:- Those substances or materials, through which things can be seen, are called transparent . For example:- Glass, water, air etc.
- Opaque:- On the other hand, there are some materials through which you are not able to see. These materials are called Opaque. For example:- wooden box , Metal Container etc.
- Translucent:- The materials through which objects can be seen, but not clearly, are known as translucent.
Materials are grouped together on the basis of similarities and differences in their properties.
Things are grouped together for convenience and to study their properties.