Need to group materials 
In everyday life, we often group materials for our convenience. At home we usually store things in such a manner that similar objects are placed together. Such an arrangement helps us to locate them easily. Similarly, a grocer usually keeps all type of biscuits at one corner of his shop all soaps at another while grains and pulses are stored at some other place. 

There is another reason why we find such grouping useful. Dividing materials in groups makes it convenient to study their properties and also observe any patterns in these properties.


1.    Hard : Materials which cannot be pressed easily are called hard e.g., stone.
2.    Insoluble : Materials which do not dissolve in water are called insoluble.
3.    Lustre : Some materials have a special shine on them which is called lustre.
4.    Material : The matter of which an object is made, is called material. For example, glass, steel, 
wood, etc.
5.    Metals : Materials which have certain properties like lustre, malleability, ductility and are sonorous, good conductors of heat and electricity, are called metals.
6.    Opaque : Materials which do not allow light to pass through them are called opaque.
7.    Rough : Some materials have uneven surface and feel rough on touching.
8.    Soluble :Materials which dssolve in water are called soluble.
9.    Translucent : Materials which partially allow light to pass through them are called translucent.
10.    Transparent : Materials which allow light to pass through them are called transparent.