Solids, liquids and gases
Everything  in the world belongs to one of these three main forms.

Have you ever wondered what everything in the world is made from? The answer to that question is matter. Matter is anything that takes up space and has mass. There are millions of different things in the world, but there are just three different forms of matter. Those are solids, liquids and gases. Everything in the world belongs to one of these three main forms. You can probably think of hundreds of different solids and liquids. Solids like stone and wood are hard and stay the same shape. Liquids like water and petrol can flow from place to place. But gases are different.

Do you know that the air around you is a mixture of gases ? 

Like most gases, you cannot see or smell the ones in the air, and it is very difficult to make them stay in one place.You can place a solid or liquid in a cup or beaker, and it will stay there.But gases must be kept in closed containers or they will escape.

How do we use gases?

There are many different kinds of gas. Some are very useful. Oxygen is an important gas. It is found in the air. It helps human and animals to stay alive, and fires to burn.  

Some gases come from under the ground. They are used as fuels, and are burned for heating and cooking. One kind of gas helps balloons to float-up in the air. Other gases help divers to breathe deep down in the sea.

gases are also used in factories to make other useful substances, such as plastics, bleach and medicines. They are used to make fertilizers, explosives and dyes.