Chemistry · Bonding, Structure and Properties of Matter
States of Matter and State Symbols
Spec 5.2.2.1–5.2.2.2📙 Higher
Theory · read, then commit
All matter exists in one of three states — solid, liquid or gas. The difference is how the particles are arranged and how freely they move.
🧊Solid
ArrangementRegular, closely packed
MovementVibrate about fixed positions
Shape & volumeFixed shape, fixed volume
Compressible?No
💧Liquid
ArrangementClose but random
MovementFlow past each other
Shape & volumeTakes container shape, fixed volume
Compressible?No
💨Gas
ArrangementFar apart, spread out
MovementFast, random, all directions
Shape & volumeFills any container
Compressible?Yes
How freely the particles move drives everything else — shape, volume and whether it can be compressed.
Checkpoint · quick check
Describe the arrangement and movement of the particles in a solid.
🫠Melting / Freezing
Solid ⇌ liquid. Melting adds energy; freezing removes it.
♨️Boiling / Condensing
Liquid ⇌ gas. Boiling adds energy; condensing removes it.
❄️Subliming
Some solids go straight to gas (iodine, dry ice). All these are physical changes.
Checkpoint · quick check
Name the change of state that occurs when a liquid turns into a gas.
🔤State symbols in equations
(s) solid · (l) liquid · (g) gas · (aq) dissolved in water.
2H₂(g) + O₂(g) → 2H₂O(l)
NaCl(s) → Na⁺(aq) + Cl⁻(aq)
Checkpoint · quick check
In the equation NaCl(s) → Na⁺(?) + Cl⁻(?), state the symbol that shows the ions are dissolved in water.
Retrieval · Match the State Change to its Name
Test yourself · 9 questions, exam order
⭐Examiner Tip
Melting and boiling are physical changes — the particles rearrange but the substance is unchanged (ice, water and steam are all H₂O), so don't call them chemical changes. And use the state symbol (aq) only for something dissolved in water, not for any liquid.
0 of 9 answered
Warm-up · 1 question
Ice melts to form water. State whether this is a physical or a chemical change, and explain your answer.
Exam standard · 4 questions
Explain, in terms of particles, why a gas can be compressed but a solid cannot.
Explain, in terms of energy and forces, what happens to the particles when a liquid boils.
As a pure solid is heated until it melts, its temperature stays constant during melting even though heating continues. Explain why.
The particle model represents particles as small solid spheres. Suggest one limitation of this model.
Stretch · 4 questions
Explain why a change of state is classed as a physical change and not a chemical change.
Predict what happens to the water particles when steam condenses on a cold window, in terms of their energy and movement.
On a graph of temperature against time, a solid is heated until it becomes a gas. Explain why the graph has two flat (horizontal) sections.
Explain why the simple particle model does not perfectly predict the properties of every substance.
Key note · cover it, say it, check it
Revision card · 5 stepsStates of Matter and State Symbols