Horrible Science: Let's play solid, liquid or gas

What are solids, liquids and gases?

A happy presenter and excited contestant stand in a tv studio playing solid, liquid or gas.

Everything around us is made from matter, which has mass (weight) and takes up space (volume).

Matter can exist in different physical states. The three main states of matter are:

Solids, which keep their shape. Ice, rocks, and pencils are solids.
Liquids, which flow and take the shape of their container. Water, milk, and lava (hot molten rock) are liquids.
Gases, which spread out to fill the space they’re in. Air, steam and helium in balloons are gases.

Watch: Let's play solid, liquid or gas

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See how Alice guesses whether objects are solid, liquid, or gas. Get ready to play along!

Why can some things be tricky to classify?

Some materials don’t fit neatly into just one state. For example:

Jelly is an example of a semi-solid. It can wobble like a liquid but still hold its shape like a solid.
Clouds may look like gas, but they’re made of tiny droplets of liquid water floating in the air.
Oobleck, made from corn flour and water, can behave like a solid when you squeeze it, but flows like a liquid when you let it sit.
Foam is made of gas trapped inside a liquid, whipped cream is an example of this. Foam is soft and fluffy but still has a definite shape.

These examples show that not everything fits neatly into solid, liquid, or gas. Some materials can act like more than one state at the same time, wobbling, flowing, or trapping air in surprising ways.

Scientists call these tricky materials ‘non-Newtonian’ or ‘complex’ because they don’t behave like the simple solids, liquids, or gases we usually see.

Horrible Science fact

Lightning might look like fire, but it’s not. It’s an example of plasma, the fourth state of matter. Plasma is an extremely hot, glowing substance made from gas that becomes so hot it can carry electricity.

When electrical charges in clouds suddenly release as a spark, the air heats up so much that it turns into plasma. Plasma also appears in very hot flames, stars and neon signs.