We know that matter is substance which has weight and occupies space. All things that have weight and takes up space are called matter.
All living things such as animals, birds and plants, and non living things such as a bat, a pencil, a piece of wood, water or air are matter. So, all the things are made of matter.
The amount of space matter takes up is called its volume. Matter has weight and takes up space because it is made up of tiny particles. These particles are much smaller than a grain of sand and they are so small that we cannot see them. Millions and millions of these tiny particles together form a table or an animal or a human being. These very tiny particles are called molecules. Molecules are not visible to our naked eyes. Molecules of different kinds of matter have different size shape and weight. For example, the molecules of apple are different from that of sugar.
Molecules of different substances are different from each other. All molecules of a particular substance keep on moving constantly. Vacant spaces lies between the molecules. The space between the molecules of a matter is called inter-molecular space.