# The States of Matter – Class 4

Everything around us is called matter. Matter is anything that has weight and takes up space. All the living things such as birds, animals and plants, and all the non-living things such as chairs, tables, balls, air and water are matter. All these things have their own weight and takes up space. Let’s learn more about the chapter – The States of Matter. This chapter is important for Class 4.

The amount of space matter takes up is called its volume.

Matter is made up of tiny particles. These particles are so small that you cannot see them with you eyes. Millions of these particles join together to form a bird or a chair. These tiny particles are called molecules. The molecules of different substances are different from each other.

### The States of Matter

Matter is found in three states – Solid, Liquid or Gas.

### Solids

Some example of solids are chair, table, ball and books. Solids have a definite shape and volume. If we pick up solids and place it somewhere else, their shape and the space they occupy do not change. In a solid, the molecules are packed close to each other (see the image given above).

### Liquids

Some examples of liquids are water, milk and juices. A liquid has a definite volume but no definite shape. Liquid takes the shape of the container in which it is kept. If we keep the liquid in a bottle, it will take the shape of a bottle. Or, if we keep the liquid in a bowl, it will take the shape of a bowl. Thus, in whatever the shape of the container we keep the liquid, it takes the shape of the container but the volume of the liquid does not change.

In a liquid, molecules are not packed as close together as they are in a solid (see the image given above). These molecules can move around more freely. Due to this free movement of molecules, liquid can flow.

### Gases

Air is a gas. In a gas, the molecules are far away from each other (see the image given above) due to which these molecules move around freely in the space available to them. A gas does not have a definite shape. Molecules of a gas can be squeezed into a small container or spread out in a big container.

A gas does not have a definite volume. When we blow air into a balloon it occupies a smaller volume. When air is let out of the balloon, it spreads all over the room to occupy a larger volume.

### Change of State

On heating, a solid becomes a liquid. On further heating, a liquid becomes a gas. For example, Ice (a solid), on heating becomes water (a liquid). On further heating, water changes into a gas called water vapour.

On cooling, the opposite changes take place. When water vapour (a gas) is cooled, it changes into water (a liquid). When water is cooled further, it changes into ice (a solid).

Thus, matter can change its state from one form to another on heating or cooling.

### Solutions

When we add a teaspoon of sugar in a glass of water and stir it, we will notice that the sugar slowly disappears. In other words, we can say that the sugar has dissolved in water.  This water tastes sweet. This sweet water is called solution of sugar in water. The sugar is called the solute. The water that dissolves the solute is called the solvent.

Solids that dissolves completely in water are called soluble substances. For example, sugar and salt are soluble substances.

Solids that do not dissolve in water are called insoluble substances. For example, sand is an insoluble substance.