We know solids, liquids and gases (i.e. all materials) occupy space. The books, schoolbag and car have a definite shape and occupy space. These objects are called solid materials. Solids have a definite shape.
Pick up any small stone, a brick, a piece of wood and a crumpled piece of paper. Place them on the table. Observe their shapes.
Now place them on the ground and again observe their shapes. Does that make any difference or changes about them?
No matter how frequently you change their places, they will not change shape.
Solid materials have definite shape.
Materials like plastic, iron, rubber, leather also have a definite shape.
Does all materials have a definite shape? No!
We have learnt that water which is a liquid and air which is a gas occupy space. Yet, they have no definite shape.
Let us find out more about the shapes of liquid and gaseous materials.
For example; take a tumbler full of water. What is the shape of the water in it? It has taken the shape of the tumbler. Pour the same water into the water bottle. It has now taken the shape of the water bottle.
Pour the same water into a mug and it takes the shape of the mug.
This shows that water has no definite shape. It takes the shape of the container it occupies. Like water, petrol, diesel and oil are other liquid materials. They also take the shape of the container into which they are poured.
Liquid materials take the shape of the container.
Similarly, air also takes the shape of its container.
Air in a football or a tyre takes the respective shapes of the football or the tyre.
Water has different forms.
Another very interesting fact about water which is a liquid, is that it can be turned to solid on cooling and to gas or vapour on heating.
Let us do an experiment on this. Take a bottle filled with water. Presently, the water is in a liquid form. Now, pour the same water in an ice-tray and keep it in the freezer. After about three hours. Remove the tray. What do we find?
The water is now in the form of ice. This is a solid form of water. Leave it out for a while, it changes into water again.
Put the same water in a pan and heat it till it boils. Does we find steam or vapour coming out and rising into the air? This vapour of water is its gaseous form.
If we continue to boil the water, it will soon evaporate into the air as vapour. Now, there is no liquid form left in the pan.
Like water, materials such as wax, coconut oil, ghee and even iron can be changed into other forms.
We use candles in our homes. Candle is solid wax. If we burn it, it melts and changes into liquid wax.
What happens to coconut oil during winter? It freezes and becomes solid. If we wish to use it, then we need to melt it by heating.
Have we seen moth balls? They are white marble sized balls kept in the cupboard to keep away insects. What happens to these balls after a few days? They turn into vapour and disappear.