What are the main states of matter covered in the IB MYP Science curriculum?

In the IB MYP Science curriculum, the main states of matter are solid, liquid, and gas. Each state has distinct properties: solids have a fixed shape and volume, liquids have a fixed volume but take the shape of their container, and gases fill the entire volume of their container.

How do the properties of matter change between different states?

The properties of matter change significantly between different states. In solids, particles are closely packed in a fixed arrangement, leading to a definite shape and volume. In liquids, particles are still close but can move past each other, allowing liquids to flow and take the shape of their container. In gases, particles are far apart and move freely, filling the entire volume of their container. These changes are due to variations in particle energy and movement.

What is the process of changing states of matter called, and how does it occur?

The process of changing states of matter is called a phase transition. Common phase transitions include melting (solid to liquid), freezing (liquid to solid), vaporization (liquid to gas), condensation (gas to liquid), sublimation (solid to gas), and deposition (gas to solid). These transitions occur due to changes in temperature and pressure, which affect the energy and movement of particles.

Why is understanding the properties of matter important in science?

Understanding the properties of matter is crucial in science because it helps explain how substances behave and interact in different environments. This knowledge is foundational for studying chemistry, physics, and biology, as it allows scientists to predict reactions, design materials, and understand natural phenomena. In the IB MYP curriculum, this understanding is essential for developing scientific inquiry and problem-solving skills.

How does temperature affect the states and properties of matter?

Temperature has a significant impact on the states and properties of matter. As temperature increases, particles gain energy and move more vigorously, which can cause a substance to change from solid to liquid (melting) or from liquid to gas (vaporization). Conversely, decreasing temperature reduces particle energy, leading to transitions from gas to liquid (condensation) or liquid to solid (freezing). These changes illustrate the dynamic nature of matter and its dependence on thermal energy.

Why is "Saying particles 'get bigger' or 'expand' when heated." a common mistake in States and Properties of Matter?

Why it happens: We see solids expand when warmed. How to avoid it: Individual particles don't change size. What changes is the SPACE between them — and how vigorously they vibrate or move.

Why is "Calling melting or boiling a chemical change." a common mistake in States and Properties of Matter?

Why it happens: It looks like the substance has changed completely. How to avoid it: State changes are PHYSICAL — the substance keeps its chemical identity. Ice, water and steam are all H₂O.

Why is "Thinking temperature keeps rising as ice melts." a common mistake in States and Properties of Matter?

Why it happens: Energy is being supplied. How to avoid it: During a state change the temperature stays constant — energy is being used to break bonds, not raise particle KE.

States of MatterIB MYP Sciences (Years 1-5)

States and Properties of Matter

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States and Properties of Matter — IB MYP Sciences: solids, liquids, gases and changes of state

All matter exists in one of three main states: solid, liquid or gas. This MYP Sciences note covers the particle model of each state, why their properties differ, the six possible state changes, and how heating and cooling drive them.

What you’ll learn

Mapped to the IB MYP Sciences subject guide (2026 onwards).

MYP Sciences A — Use the particle model to explain the properties of each state.
MYP Sciences A — Name and describe each of the six state changes.
MYP Sciences A — Distinguish between melting/freezing and evaporation/boiling.
MYP Sciences C — Read a heating curve and identify state changes.
MYP Sciences D — Apply the particle model to everyday phenomena (rain, frost, condensation on a glass).

The three states of matter

Solid: fixed. Liquid: flows. Gas: fills any container.

Matter exists in three common states. The differences come down to particle arrangement and energy.

State	Arrangement	Movement	Shape	Volume
Solid	Regular, tightly packed	Vibrate in place	Fixed	Fixed
Liquid	Close together but disorderly	Slide past each other	Takes container shape	Fixed
Gas	Far apart, random	Move freely at high speed	Fills container	Fills container

Particle arrangements: solids close + ordered, liquids close + jumbled, gases far apart.

Solid: fixed shape and volume.
Liquid: fixed volume, takes container shape.
Gas: fills any container completely.

Six state changes

Six possible transitions between the three states.

Between the three states there are SIX possible transitions:

Solid → Liquid: melting (e.g. ice → water at 0 °C).
Liquid → Solid: freezing (e.g. water → ice at 0 °C).
Liquid → Gas: evaporating (slow, at surface, any temperature) OR boiling (rapid, throughout liquid, at boiling point).
Gas → Liquid: condensing (e.g. steam → water on a cold surface).
Solid → Gas: subliming (e.g. dry ice, iodine).
Gas → Solid: depositing (e.g. frost on a cold window).

Each state change happens at a specific transition temperature (melting point, boiling point). The energy supplied during a state change goes into BREAKING bonds between particles, NOT into raising temperature — which is why heating curves show plateaus.

State changes are physical changes — the substance keeps its chemical identity, just changing how its particles are arranged.

6 changes between 3 states (each pair has 2 directions).
Evaporation = slow, surface only. Boiling = rapid, throughout, at boiling point.
State changes are PHYSICAL, not chemical.

Explaining the properties

The particle model explains every property of each state.

Why does each state behave as it does? Particles!

Solids are rigid because particles are locked in place by strong bonds — they only vibrate.
Liquids flow because particles can slide past each other but are still close.
Gases fill containers because particles move freely at high speed in all directions.
Solids and liquids are incompressible (or nearly so) because particles are already touching — nowhere to compress to.
Gases compress easily because there's lots of space between particles.
Diffusion (one fluid spreading through another) happens in liquids and gases because particles move. It happens FASTER in gases because particles move faster and have more space.
Heating gives particles more kinetic energy. In solids they vibrate more violently; in liquids and gases they move faster. Enough heating breaks the bonds → state change.

Solids rigid: strong bonds, particles locked.
Liquids flow: particles slide past each other.
Gases compress: lots of empty space.
Diffusion fastest in gases (particles move fastest, most space).

How it’s examined

Criterion A tests the particle model and the 6 state changes. Criterion C presents a heating curve and asks you to identify each plateau and slope. Criterion D often asks you to apply the particle model to everyday examples (puddles drying, ice cubes melting, fog forming).

Sources: IB MYP Sciences guide (IBO, official subject guide). Last reviewed 2026-05-25.

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Step-by-step worked examples — States and Properties of Matter

Step-by-step solutions to past-paper-style questions on states and properties of matter, written exactly the way a tutor would explain them at the board.

1Name the state change
Getting started• state changes
Question
Name the state change in each: (a) ice cube melts in a drink, (b) steam fogs up a mirror, (c) dry ice (solid CO₂) turns directly to gas, (d) frost forms on a window.
Step-by-step solution
1. Step 1
  (a) Solid → liquid = MELTING.
2. Step 2
  (b) Gas → liquid = CONDENSING.
3. Step 3
  (c) Solid → gas = SUBLIMING.
4. Step 4
  (d) Gas → solid (water vapour to ice) = DEPOSITING.
Answer
(a) melting, (b) condensing, (c) subliming, (d) depositing.
2Evaporation vs boiling
Building confidence• evaporation
Question
Compare evaporation and boiling — give two clear differences.
Step-by-step solution
1. Step 1
  Evaporation happens at the SURFACE only; boiling happens THROUGHOUT the liquid (bubbles form anywhere).
2. Step 2
  Evaporation happens at ANY temperature; boiling only at (or above) the BOILING POINT.
Answer
Evaporation: surface only, any temperature. Boiling: throughout, only at the boiling point.
3Explaining a property
Stretch• particle model
Question
Why are gases much easier to compress than liquids?
Step-by-step solution
1. Step 1
  In a gas, particles are spread far apart with lots of empty space between them.
2. Step 2
  Squeezing the gas pushes the particles closer together — easy to do because there's plenty of room.
3. Step 3
  In a liquid, particles are already in contact — there's almost no empty space to compress into.
Answer
Gases have lots of empty space between particles, so they can be squeezed closer together. Liquid particles are already touching, leaving almost nowhere to compress to.

Key Definitions and Keywords — States and Properties of Matter

Definitions to memorise and the exact keywords mark schemes credit for states and properties of matter answers — sharpened from recent examiner reports for the 2026 IB MYP Sciences sitting.

State of matter
Examiner keyword
A distinct physical form a substance takes: solid, liquid or gas (or plasma at very high temperatures).
Melting / freezing
Examiner keyword
Solid ↔ liquid transitions. Both happen at the same temperature for a substance (melting point).
Evaporation
Examiner keyword
Liquid → gas at the surface only; can happen at any temperature.
Boiling
Examiner keyword
Liquid → gas throughout the liquid (bubbles form inside it). Happens only at the boiling point.
Condensing
Gas → liquid (on cooling).
Subliming
Solid → gas without going through liquid first (e.g. dry ice, iodine).
Depositing
Gas → solid without going through liquid first (e.g. frost).
Particle model
Examiner keyword
The picture of matter as made of small moving particles. Used to explain properties and state changes.

Common Mistakes and Misconceptions — States and Properties of Matter

The traps other students keep falling into on states and properties of matter questions — taken from recent IB MYP Sciences examiner reports and mark schemes — and how to avoid them.

✕Saying particles 'get bigger' or 'expand' when heated.
Why it happens
We see solids expand when warmed.
How to avoid it
Individual particles don't change size. What changes is the SPACE between them — and how vigorously they vibrate or move.
✕Calling melting or boiling a chemical change.
Why it happens
It looks like the substance has changed completely.
How to avoid it
State changes are PHYSICAL — the substance keeps its chemical identity. Ice, water and steam are all H₂O.
✕Thinking temperature keeps rising as ice melts.
Why it happens
Energy is being supplied.
How to avoid it
During a state change the temperature stays constant — energy is being used to break bonds, not raise particle KE.

Practice questions

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States and Properties of Matter — frequently asked questions

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States and Properties of Matter

Short Study Notes in the form of Slides

Short Study Notes — States and Properties of Matter

Detailed Notes

What you’ll learn

How it’s examined

1Name the state change

2Evaporation vs boiling

3Explaining a property

State of matter

Melting / freezing

Evaporation

Boiling

Condensing

Subliming

Depositing

Particle model

✕Saying particles 'get bigger' or 'expand' when heated.

✕Calling melting or boiling a chemical change.

✕Thinking temperature keeps rising as ice melts.

Practice questions

Past paper style quiz

Assess your understanding

States and Properties of Matter — frequently asked questions