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Solids, liquids and gases

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Solids, Liquids & Gases

Materials exist as solids, liquids and gases, and as a mixture of these states. They may be natural or man made and they have different textures and properties.

The properties of solids, liquids and gases

Some solids are hard and strong, others are flexible. Most solids will melt when heated and liquids evaporate to form a gas.

Cartoon animations explain in simple terms why different materials have different properties and how they change on heating and cooling. Other animations cover separating solids from liquids and show what happens to a solid when it dissolves in a liquid.

Use the links below to see short video clips illustrating the different states of matter.


A solid keeps its shape unless a force is put on it.

They changed their shape if you

squash them,

twist them,

or cut them.

Solids do not change shape on their own.

They do not have to be hard.

They can be soft,


or even fluffy.

Words used to describe solids are called properties.

Knowing the properties of materials can help you decide which ones to use.

Changing solids to liquids.

When you heat some solids, they melt and become liquid.

Different materials melt at different temperatures.

This is called the melting point.

The melting point of water is 0 degrees celsius.

This is when ice (solid water) becomes a liquid.

At room temperature, water is a liquid.

Butter is a solid at room temperature.

If you heat butter, it will allow to become a liquid.

Gold is a solid room temperature if you heat it to 1064 degrees celsius it will melt and become liquid gold.


Gases will spread out to fill a container.

Or just keep spreading around.

Gases have weight because they are affected by gravity.

Solids to liquids to gas.

In a solid, the particles are packed tightly and together and vibrate slowly.

As the solid heats up the particles vibrate more and take up more space.

The solid no longer keeps its shape and becomes a liquid.

If the liquid is heated more, the particles vibrate so much that they begin to escape from the liquid.

Single particles are so small you cannot see them and they spread out as a gas.

More about dissolving.

Dissolving is separating into particles too small to see.

This is called a solution.

If a solid has dissolved it can be got back by evaporating the liquid.

Not all solids dissolve this mixture is called a suspension.


Liquids take the shape of the container that they are in.

Liquids are pulled by gravity down

to the bottom of a container.

when you move a liquid into different containers the shape changes,

but the volume does not.


When you mix solids with liquids, some will sink, and some will float.

Some solids will get smaller and smaller

until you can't see them anymore.

That is because the solids are dissolving to make a new liquid called a solution

Dissolving is when the solid separates into particles too small to see.

Solids, liquids and gases.

A solid keeps its shape unless a force changes it.

Liquids take the shape of the container that they are in.

Gases have no fixed shape or volume.

Changing states of water.

When the water is boiling we see bubbles but these are not bubbles of air they are bubbles of water that have changed state to a gas.

This happens at approximately 100 degrees celsius.

You need to give the water energy, heat, to turn it into a gas.

If you change the amount of heat it can change how fast the water changes state into a gas.

Reversible and non-reversible changes.

Some changes are reversible.

Once you have changed something you can change
it back.

Like melting ice to liquid then refreezing
it again.

Some changes are non-reversible.

Once you have changed something you can not
change it back, like cooking an egg.

Or mixing flour and milk.

Or burning a match.