Anything that occupies space and has weight and can be felt by our senses is called matter.
Three states of matter
Materials are of three types – solids, liquids and gases.
A solid has a definite shape and volume. It retains its shape wherever it is placed e.g., stone, wood, iron, pen book, leather etc.
A liquid has a definite volume but no definite shape. It takes the shape of the container in which it is put. All liquids are flow e.g., water, milk, oil, petrol etc.
A gas has neither definite volume nor definite shape. It also takes the shape of the container e.g., air, cooking gas, oxygen, nitrogen etc.
Air is mixture of a number of gases. Nitrogen is the major portion of the air.
Solids have definite shapes whereas liquids and gases have no definite shape. Liquids and gases can spread or flow whereas solids cannot flow.
A liquid can fill a part of the container while a gas always fills entire space inside the container.
The three states of matter are inter changeable
The same matter can exist in three different forms. Three states in which water exists are ice which is a solid, water which is a liquid and steam which is gas. The three states are interchangeable. Ice changes into water on heating. Water changes into vapor or steam when heated further. The reverse is also true. If we cool steam it changes into water and water when cooled sufficiently in a refrigerator, changes into ice. Candle wax, butter and certain other oils exist in two states.
Use of materials
Solids are used for the construction of buildings, furniture and vessels. Liquids are used as drink, petrol as fuel, oil for cooking. Air is used in inflating bicycle and car tyers, football bladders etc. cooking gas is used a fuel.