KS2 Science · States of matter · Year 4
Solids, liquids and gases
The three states of matter and how materials change between them.
About 20 minutes
Step 1 · Wonder why it matters
Hook
Where did the puddle go?
After the rain there are puddles everywhere. A few hours later, they have vanished. The water did not soak away on the playground — so where did it go?
The answer is that it changed state: from a liquid into a gas.
Step 2 · See it
Picture
See the particles
Everything is made of tiny particles. How they are arranged decides whether a material is a solid, liquid or gas.
| Solid | Liquid | Gas | |
|---|---|---|---|
| Particles | Packed in rows, touching | Touching, but jumbled | Far apart |
| Movement | Vibrate on the spot | Slide past each other | Zoom in all directions |
| Shape | Keeps its shape | Takes the shape of its container | Fills any container |
| Example | Ice | Water | Steam (water vapour) |
Step 3 · Understand how it works
Logic
Changing state
Heating gives particles more energy, so they move more. Cooling takes energy away.
Melting: solid → liquid when heated. Ice melts at 0 °C.
Freezing: liquid → solid when cooled. Water freezes at 0 °C.
Evaporating: liquid → gas. Water boils at 100 °C, but it also evaporates slowly at lower temperatures — that is what happened to the puddle.
Condensing: gas → liquid when cooled, like water droplets forming on a cold window.
- Solid
- melts →
- Liquid
- evaporates →
- Gas
- Melting
- A solid turning into a liquid.
- Evaporation
- A liquid turning into a gas.
- Condensation
- A gas turning into a liquid.
- Freezing
- A liquid turning into a solid.
Step 4 · Have a go
Do
Investigate
You need two ice cubes, two saucers and a grown-up.
- 1Put one ice cube on a saucer in a warm, sunny spot and one in a cool, shady spot.
- 2Predict which will melt first, and write down why.
- 3Check every 5 minutes and note what you see.
- 4Breathe on a cold mirror. What forms? Which change of state is that?
Step 5 · Remember it
Recall
Quick quiz
Name the change of state.
0 of 4 answered
1.Which state keeps its own shape?
2.What is it called when a liquid turns into a gas?
3.At what temperature does water freeze?
4.Droplets form on a cold can of drink. This is…
Step 6 · Link it to your world
Reflect
Think about it
Changes of state are happening all around you.
Find one change of state in your kitchen. Which change is it, and what causes it?
Saved to your notebook on this device only.
Finished all six steps?
Mark it complete to collect 3 stars. That's the last lesson in this course for now.