IGCSE Physics States of Matter Questions and Worked Solutions (2.1.1) | 0625

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IGCSE Physics 0625 · Topic 2.1.1

IGCSE Physics States of Matter Questions and Worked Solutions

50 topic-wise practice questions on States of Matter (Unit 2: Thermal Physics), written to the Cambridge IGCSE Physics 0625 syllabus for 2026–2028, each with a step-by-step worked solution.

50 questions40 Core0 Extended10 Challenge100 marksTextbook §2.1 · pp. 86–99
Questions tagged Core are for all candidates (Papers 1 & 3). Questions tagged Extended are Supplement content (Papers 2 & 4). Questions 41–50 are harder Challenge questions. Try each question first, then tap Show solution to check your working.

Topic guide: States of Matter

Matter exists as solids, liquids and gases. Each state has typical properties of shape, volume and compressibility, and substances change state at their melting and boiling points.

Key formulas

No equations to learn in this subtopic — learn the properties and names of changes of state.

Prerequisite knowledge

  • Everyday experience of ice, water and steam

Exam tips & common mistakes

  • Use the correct name 'solidification' or 'freezing' — not 'solidifying out'
  • Compare a substance's temperature with its melting and boiling points to decide its state
  • Liquids and gases are both fluids (they flow)

Key facts from the syllabus (2.1.1)

  • Solids: fixed shape and volume, very hard to compress
  • Liquids: fixed volume, take the shape of their container, very hard to compress, can flow
  • Gases: no fixed shape or volume, fill their container, easily compressed, can flow
  • Changes of state: melting, boiling (and evaporation), condensation, solidification (freezing)
  • Pure water melts at 0 °C and boils at 100 °C at standard atmospheric pressure
  • Energy is absorbed when melting and boiling and released when condensing and solidifying

Textbook: §2.1 Kinetic particle model of matter, pp. 86–99

1
Core[1 mark]

State the three states of matter.

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Method: Solid, liquid, gas.

Solid, liquid and gas
2
Core[2 marks]

State two properties of a solid.

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Method: Fixed shape and volume.

Fixed shape and fixed volume (cannot be compressed easily)
3
Core[2 marks]

State two properties of a liquid.

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Method: Flows; fixed volume.

Fixed volume but takes the shape of its container; hard to compress
4
Core[2 marks]

State two properties of a gas.

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Method: No fixed shape or volume; compressible.

No fixed shape or volume; fills its container; easily compressed
5
Core[1 mark]

Name the change of state from solid to liquid.

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Method: Melting.

Melting
6
Core[1 mark]

Name the change of state from liquid to gas at the boiling point.

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Method: Boiling.

Boiling
7
Core[1 mark]

Name the change of state from gas to liquid.

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Method: Condensation.

Condensation
8
Core[1 mark]

Name the change of state from liquid to solid.

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Method: Solidification.

Solidification (freezing)
9
Core[1 mark]

State which state of matter is most easily compressed.

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Method: Gas particles are far apart.

Gas
10
Core[1 mark]

State which states of matter can flow.

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Method: Liquids and gases.

Liquids and gases
11
Core[2 marks]

Water vapour forms droplets on a cold window. Name this change of state and state whether energy is given out or taken in.

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Method: Gas → liquid releases energy.

Condensation; energy is given out
12
Core[2 marks]

Ice cubes left on a table become water. Name the process and state whether energy is absorbed or released.

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Method: Melting absorbs energy.

Melting; energy is absorbed from the surroundings
13
Core[2 marks]

State which state of matter has a fixed volume but no fixed shape.

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Method: Liquid.

Liquid
14
Core[2 marks]

Explain why a gas fills any container it is placed in.

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Method: Particles move freely in all directions.

Its particles move randomly and freely in all directions until they spread throughout the container
15
Core[1 mark]

Name the process where a liquid turns into a gas at its surface below the boiling point.

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Method: Evaporation.

Evaporation
16
Core[2 marks]

Molten wax cools and hardens in a mould. Name the change of state and state one property of the new state.

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Method: Liquid → solid.

Solidification; it now has a fixed shape
17
Core[2 marks]

A syringe of air is sealed and the plunger is pushed in. State what happens to the volume and explain using a property of gases.

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Method: Gases are compressible.

The volume decreases because gases can be compressed
18
Core[2 marks]

A syringe full of water is sealed and the plunger is pushed. State what happens and why.

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Method: Liquids are nearly incompressible.

The volume hardly changes because liquids are very difficult to compress
19
Core[1 mark]

State the melting point of pure ice at standard atmospheric pressure.

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Method: 0 °C.

0 °C
20
Core[1 mark]

State the boiling point of pure water at standard atmospheric pressure.

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Method: 100 °C.

100 °C
21
Core[2 marks]

Compare the volume of 1 kg of water as a liquid and as steam.

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Method: Gas spreads out.

Steam occupies a much larger volume
22
Core[1 mark]

Name the change of state when a puddle dries up on a warm day.

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Method: Below boiling point.

Evaporation
23
Core[2 marks]

A sample is heated and its temperature stays constant at 78 °C while bubbles form throughout. Name the process and suggest what 78 °C is.

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Method: Boiling.

Boiling; 78 °C is its boiling point
24
Core[2 marks]

State the change of state that occurs when molten iron is poured into a mould and cools.

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Method: Liquid → solid.

Solidification
25
Core[2 marks]

Explain why a gas can be stored in a small cylinder under pressure.

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Method: Compressible.

Gases can be compressed into a much smaller volume
26
Core[2 marks]

Explain why liquids are used in hydraulic brakes.

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Method: Incompressible.

Liquids are almost incompressible, so pressure is transmitted through them
27
Core[2 marks]

Water at 20 °C is put into a freezer. Name the two processes as it becomes ice at −10 °C.

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Method: Cooling and freezing.

Cooling, then solidification (freezing) at 0 °C, then cooling of the ice
28
Core[1 mark]

State the state of oxygen at room temperature.

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Method: Gas.

Gas
29
Core[2 marks]

A substance has a melting point of −39 °C and a boiling point of 357 °C. State its state at 25 °C.

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Method: Between mp and bp.

Liquid
30
Core[2 marks]

A substance melts at 801 °C and boils at 1413 °C. State its state at 1000 °C and at 1500 °C.

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Method: Compare.

1000 °C: liquid; 1500 °C: gas
31
Core[2 marks]

State the change of state that happens when steam touches a cold mirror.

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Method: Gas → liquid.

Condensation
32
Core[2 marks]

Explain why you can smell perfume across a room.

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Method: Gas spreads.

The perfume evaporates and the gas particles spread out through the air
33
Core[2 marks]

State two differences between a solid and a gas.

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Method: Shape, volume, compressibility.

A solid has a fixed shape and volume and is hard to compress; a gas has neither and is easily compressed
34
Core[1 mark]

State the term for the temperature at which a solid turns into a liquid.

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Method: Melting point.

Melting point
35
Core[1 mark]

State the term for the temperature at which a liquid turns into a solid.

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Method: Freezing point.

Freezing (solidification) point, equal to the melting point
36
Core[2 marks]

Chocolate melts in your hand. State whether energy is taken from or given to your hand.

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Method: Melting absorbs energy.

Energy is taken from your hand
37
Core[2 marks]

State which state of matter has a fixed shape.

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Method: Solid.

Solid
38
Core[2 marks]

Explain why a liquid takes the shape of its container but a solid does not.

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Method: Flow.

Liquid particles can move past each other (flow); solid particles are fixed in place
39
Core[2 marks]

A metal is cooled from liquid to solid. State what happens to its volume (for most substances).

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Method: Decreases slightly.

It decreases slightly
40
Core[1 mark]

State the change of state that is the reverse of boiling.

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Method: Condensation.

Condensation

Challenge questions

Harder, multi-step questions at the top end of the exam. Attempt these once you are confident with the questions above.

41
ChallengeCore[4 marks]

A substance has melting point −7 °C and boiling point 59 °C. State its state at −20 °C, 20 °C and 80 °C, and name the change of state when it is cooled from 80 °C to 20 °C.

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Method: Compare with mp and bp.

Solid, liquid, gas; condensation
42
ChallengeCore[4 marks]

Compare solids, liquids and gases in terms of shape, volume and ability to flow, and use this to explain why a gas can be stored in a cylinder but a solid cannot be squeezed into one.

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Method: Properties table.

Solid: fixed shape and volume, no flow; liquid: fixed volume, takes container shape, flows; gas: no fixed shape or volume, flows, compressible — so gases can be compressed into cylinders
43
ChallengeCore[3 marks]

Explain why a bicycle tyre filled with air gives a softer ride than one filled with water.

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Method: Compressibility.

Air is compressible so it squashes and absorbs bumps; water is nearly incompressible
44
ChallengeCore[4 marks]

A beaker of ice at −10 °C is heated steadily until it becomes steam at 110 °C. List, in order, the changes of state and the stages where the temperature rises.

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Method: Heating curve.

Ice warms to 0 °C; melts at 0 °C; water warms to 100 °C; boils at 100 °C; steam warms to 110 °C
45
ChallengeCore[3 marks]

Explain why the volume of a liquid stays almost the same when poured into a different-shaped container but its shape changes.

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Method: Particles close but mobile.

Particles stay close together (fixed volume) but can move past each other (shape changes)
46
ChallengeCore[4 marks]

Mercury melts at −39 °C and boils at 357 °C. Explain why it can be used in a thermometer to measure the boiling point of water but not the temperature in Antarctica at −60 °C.

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Method: Liquid range.

At 100 °C mercury is liquid; at −60 °C it is solid, so it cannot expand along the tube
47
ChallengeCore[3 marks]

Explain how you could show that a gas has mass.

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Method: Weigh before and after.

Weigh a sealed, pumped-up ball, let some air out and weigh again — the mass decreases
48
ChallengeCore[3 marks]

Explain why evaporation and boiling are both described as changes from liquid to gas but are different processes.

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Method: Surface vs throughout.

Both change liquid to gas, but evaporation occurs at the surface at any temperature while boiling occurs throughout at the boiling point
49
ChallengeCore[4 marks]

A solid is heated and its temperature recorded every minute: 20, 35, 50, 62, 62, 62, 62, 75, 88 °C. State the melting point and explain what is happening between minutes 3 and 6.

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Method: Flat section.

Melting point 62 °C; the solid is melting — energy separates particles so the temperature stays constant
50
ChallengeCore[3 marks]

Explain why liquids and gases are both called fluids but only gases are easily compressed.

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Method: Flow vs spacing.

Both flow because particles can move past each other; only in gases are the particles far apart, leaving space to compress
All IGCSE Physics topics← 1.8 Pressure2.1.2 Particle Model →

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