���˿���

What do steam, a bicycle, and a cup of tea all have in common? They are all made of matter.

Now imagine a mountain, a lake and air.These three things are the three states in which matter occurs: solids, liquids, and gases.

Mountains are made from rock. Rock is an example of a solid. A lake is made up of water. This is an example of a liquid. The air we breathe is a gas.

Solids

A solid, such as a table, has a definite shape that is difficult to change.

This is because the particles of a solid have very firm bonds, which means solids are usually difficult to break.

Most solids are hard. Some examples of hard solids include mountains, tables, books, and balls.

Solids such as rubber have a shape that can be changed.

Liquids

So what do liquids have in common with each other? Well, for a start, liquids can flow. They do not have fixed shapes.

A liquid's shape changes to fit its container. However, they do have a fixed volume.

Next time you have a drink, look carefully inside your glass. The liquid you are drinking has taken on the shape of the glass.

However, if you spilt that drink, the shape of the liquid changes. And if you pour any remaining liquid into a different container, the shape of the liquid changes. But the volume remains the same.

Water is the most common liquid and is essential for life. It is found in oceans, rivers, lakes, and even in the air as water vapour.

Gases

Now let's think about gases. A gas quickly fills any space it is put into because its particles move fast.

This means that a gas takes the shape of its container. For example, we fill balloons up with the gas helium.

Gases do not have fixed shapes, and they move easily. We are not able to see most.

For example, we walk through the air when we're walking about during our day. Mostly we cannot see this air or even feel the air.

Using states of matter

The three states of matter (solids, liquids and gases) are all around us and are used in many different ways.

A bicycle is a great way to see three states of matter existing together in one place. Many parts of a bicycle are made of solids. A bicycle frame is solid, as are the wheels.

Your bicycle tyres are filled with air, a gas. And the oil on your bicycle chain is an excellent example of a liquid.

Changes of state

Matter can change from one state to another, for example, a liquid into a solid or a gas into a liquid. How can we change liquids into solids? We need either a change in temperature or pressure.

Let's use water as it as a perfect example. How does water turn into ice? Through freezing, when the temperature becomes really cold.

And how does ice turn into water? When the temperature is hot enough, ice melts.

Water is unusual as it can be found in all three states of matter.

In solid form, water is ice; in liquid form, water and, as a gas, steam. In all three different states, water is essential to everything on Earth.