States of Matter
Everything around us is made of matter. Matter can exist in three different states — solid, liquid, and gas. Let's explore each one!
What Is Matter?
Matter is anything that takes up space and has mass. Your desk, the water in your drink bottle, and even the air you breathe are all matter. Scientists group matter into three main states.
Solid
Keeps its shape
Liquid
Flows and pours
Gas
Spreads to fill space
Solids
A solid has a fixed shape and a fixed volume. It does not flow or spread out. The particles in a solid are packed tightly together.
Properties of Solids
- ✓ Keeps its own shape
- ✓ Does not flow
- ✓ Cannot be easily compressed
- ✓ Has a fixed volume
Examples of Solids
Think About It!
If you put a rock into a square box and then a round bowl, what happens to its shape? A solid keeps its own shape — it does NOT change shape to fit its container.
Liquids
A liquid has a fixed volume but takes the shape of its container. Liquids can flow and pour. The particles in a liquid are close together but can slide past each other.
Properties of Liquids
- ✓ Takes the shape of its container
- ✓ Has a fixed volume
- ✓ Can flow and be poured
- ✓ Has a flat surface (called a meniscus)
Examples of Liquids
Key Idea
Pour water from a square container into a round glass — the water changes shape but the amount of water stays the same. Volume stays fixed; shape changes.
Gases
A gas has no fixed shape and no fixed volume. Gases spread out to fill any container they are in. The particles in a gas move quickly and are far apart.
Properties of Gases
- ✓ No fixed shape
- ✓ No fixed volume
- ✓ Spreads out to fill its container
- ✓ Can be compressed (squashed)
Examples of Gases
Did You Know?
You cannot see most gases! Air is all around you but is invisible. Steam from a kettle is water turning into a gas called water vapour.
Changing States
Matter can change from one state to another when it is heated or cooled. These changes happen to the same material — no new substance is created.
SOLID
e.g. Ice
Heat up →
⇄
← Cool down
LIQUID
e.g. Water
Heat up →
⇄
← Cool down
GAS
e.g. Steam
Melting and Boiling (heating)
- Melting: solid becomes a liquid (ice melts to water)
- Evaporation/Boiling: liquid becomes a gas (water boils to steam)
Freezing and Condensing (cooling)
- Freezing: liquid becomes a solid (water freezes to ice)
- Condensation: gas becomes a liquid (steam cools to water droplets)
Key Vocabulary
Matter
Anything that takes up space and has mass. Solids, liquids, and gases are all matter.
Solid
A state of matter with a fixed shape and fixed volume. Particles are packed tightly together.
Liquid
A state of matter that flows and takes the shape of its container, but keeps a fixed volume.
Gas
A state of matter with no fixed shape or volume. Gas particles spread out to fill their container.
Melting
When a solid is heated and changes into a liquid (e.g. ice melting into water).
Evaporation
When a liquid is heated and changes into a gas (e.g. water turning to steam).
Knowledge Check
Choose the correct answer for each question. Click "Check Answer" to see if you are right!
Question 1
Which of these is a solid?
Question 2
What happens to water when it is heated enough?
Question 3
You pour water from a square container into a round glass. What changes?
Question 4
When water in a puddle disappears on a warm day, what has happened?
Question 5
Which statement about gases is correct?
Key Concepts Summary
- ●Matter is anything that takes up space and has mass.
- ●Solids have a fixed shape and fixed volume — particles are tightly packed.
- ●Liquids take the shape of their container but keep a fixed volume — particles slide past each other.
- ●Gases spread to fill any container — particles move quickly and are far apart.
- ●Matter changes state when heated (melting, evaporation) or cooled (freezing, condensation).