States Of Matter — 3–5 Science | Scholars & Parents

What Is This?

Matter is anything that has mass and takes up space — which includes virtually everything in the physical world. Matter exists in three common states (and a fourth, plasma, encountered less often in everyday life): solid, liquid, and gas. The state of matter depends on how the particles that make up the substance are arranged and how much energy they have.

Why Does It Matter?

Understanding states of matter explains an enormous range of everyday phenomena — why ice melts into water, why water boils into steam, why metals can be melted and shaped, why balloons expand when heated, and how cooking, refrigeration, and countless industrial processes work. It also introduces the particle model of matter — the idea that all matter is made of tiny particles whose behavior explains the properties we observe.

The Three States of Matter

Solid

Properties:

Has a definite shape — it keeps its shape regardless of the container
Has a definite volume — it takes up a fixed amount of space
Particles are packed closely together in a fixed, ordered arrangement
Particles vibrate in place but cannot move past each other

Examples: Ice, rock, wood, metal, a pencil

Liquid

Properties:

Has no definite shape — it takes the shape of its container
Has a definite volume — the total amount of liquid stays the same even as its shape changes
Particles are close together but can flow and slide past each other
More loosely arranged than solids

Examples: Water, milk, juice, mercury, lava

Gas

Properties:

Has no definite shape — it takes the shape of its container
Has no definite volume — it expands to fill whatever container it is placed in
Particles are far apart and move rapidly in all directions
Can be compressed (squeezed into a smaller space)

Examples: Air, water vapor, oxygen, carbon dioxide, helium

Comparing the Three States

Property	Solid	Liquid	Gas
Definite shape	Yes	No	No
Definite volume	Yes	Yes	No
Particle arrangement	Tightly packed, ordered	Close, can flow	Far apart, random
Can be compressed	No	Barely	Yes

Changes of State

Matter can change from one state to another when energy (usually in the form of heat) is added or removed. These changes of state are physical changes — the chemical identity of the substance stays the same; only its physical form changes.

Adding Heat (Energy Added)

Melting: Solid → Liquid (e.g., ice melting into water)
Evaporation/Boiling: Liquid → Gas (e.g., water heating into steam)
Sublimation: Solid → Gas directly, without becoming liquid (e.g., dry ice/solid CO₂ turning directly into carbon dioxide gas)

Removing Heat (Energy Removed)

Freezing: Liquid → Solid (e.g., water freezing into ice)
Condensation: Gas → Liquid (e.g., water vapor in air cooling into water droplets on a cold glass)
Deposition: Gas → Solid directly (e.g., frost forming directly from water vapor on a cold surface)

Key Temperatures for Water

Water is the most familiar example of a substance that exists naturally in all three states:

Freezing/Melting point: 0°C (32°F) — water freezes to ice below this temperature; ice melts above it
Boiling/Condensation point: 100°C (212°F) at sea level — water boils into steam above this temperature

Physical vs. Chemical Changes

A physical change alters the form or appearance of matter but does not change its chemical identity:

Ice melting into water is a physical change — it is still H₂O
Cutting paper is a physical change — the paper is still paper

A chemical change produces an entirely new substance with different properties:

Burning paper is a chemical change — it produces ash, carbon dioxide, and water, which are different substances

Changes of state are always physical changes — the substance does not become something chemically different.

A Fourth State: Plasma

Plasma is sometimes called the fourth state of matter. It forms when gas particles are given so much energy that electrons separate from their atoms, creating a mix of charged particles. Plasma is the most common state of matter in the universe — stars, including the Sun, are made almost entirely of plasma. It also appears in lightning bolts, neon signs, and plasma TVs.

Common Mistakes

Mistake 1: Thinking liquids have no definite volume

Liquids have no definite shape (they take the shape of their container) but they DO have a definite volume — pour 500 mL of water from a tall cylinder into a wide bowl, and it is still 500 mL.

Mistake 2: Thinking changes of state are chemical changes

When water boils or ice melts, the substance is still water (H₂O) — only its physical state changes. Chemical changes produce new substances; physical changes like state changes do not.

Mistake 3: Thinking air has no matter

Air is a mixture of gases — it has mass and takes up space, making it matter. This can be demonstrated by inflating a balloon (it gets heavier) or compressing air in a bicycle pump.

Key Takeaways

Matter exists in three common states: solid (definite shape and volume), liquid (definite volume, no definite shape), gas (no definite shape or volume)
The state depends on particle arrangement and energy — closely packed/ordered in solids, flowing in liquids, widely spread in gases
Adding heat: melting (solid→liquid), evaporation/boiling (liquid→gas), sublimation (solid→gas)
Removing heat: freezing (liquid→solid), condensation (gas→liquid), deposition (gas→solid)
Changes of state are physical changes — the chemical identity of the substance does not change
Water freezes at 0°C and boils at 100°C (at sea level)

Practice and Resources

Ready to practise? Try our Grade 3-5 States of Matter Worksheet with state identification, change-of-state sequencing, and property comparison activities. Test yourself with the Grade 3-5 Science Practice Test.