Solids, liquids and gases
How can ice, water and steam all be the very same stuff?
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Explain
Ice is solid, and water is runny.
Steam floats away.
Most things can be a solid, a liquid or a gas. These are called states of matter.
In solids, particles are held tightly and only shake. In liquids, they slide past each other. In gases, they fly about freely.
Heating gives particles more energy, so ice can turn to water, and water to steam.
Temperature measures the average kinetic energy of particles.
Solids keep their shape and volume. Liquids keep their volume but flow. Gases fill any space, and can be compressed.
Water is unusual: it expands when it freezes, which is why ice floats.
- Solid: particles held tight
- Liquid: particles slide
- Gas: particles fly apart
Want the full story?
The sim shows particles far apart for clarity. Real liquids are nearly as closely packed as solids. Particles in a gas move in straight lines until they hit something. Other states exist too, such as plasma in stars.
Try it at home
You need ice cubes, a plate, a pan lid.
You need: ice cubes, a plate, a pan lid.
Watch an ice cube melt on a plate.
- Put an ice cube on a plate.
- Watch it turn into water.
- Leave the plate on a sunny windowsill until the water is gone.
What's happening: the ice takes in heat and melts. Then water particles escape into the air as a gas.
Physics is life
Your body
You breathe gas and drink liquid.
Daily life
Ice cubes melt in a drink.
Nature
Rain falls from clouds.
Space
Stars are super hot gas.
Quick check
Question 1 of 3
Words to know
Solid: Matter with a fixed shape, like a rock.