GCSE Physics resources
AQA GCSE Particle model of matter
A temperature rise and a change of state both increase internal energy, but they require different equations and different particle explanations.
Start here
A temperature rise and a change of state both increase internal energy, but they require different equations and different particle explanations.
Before you revise
Choose an answer from memory. Your result tells you what to watch for in the guide.
Core revision guide
A temperature rise and a change of state both increase internal energy, but they require different equations and different particle explanations.
Scope: 8463 and 8464 · Foundation and Higher
Internal energy is the total kinetic and potential energy of the particles. Temperature is related to their average kinetic energy, not their total internal energy. During a rising section of a heating curve particles gain average kinetic energy. E = mcΔθ uses c in J/(kg °C) and a temperature difference, not the final temperature.
Scope: 8463 and 8464 · Foundation and Higher
Specific latent heat L is energy needed per kilogram to change state without changing temperature; its unit is J/kg. Fusion is solid to liquid; vaporisation is liquid to gas. E = mL. While a pure substance melts or boils at steady pressure, energy changes particle potential energy and arrangements rather than average kinetic energy. Constant temperature does not mean zero energy transfer.
Scope: 8463 and 8464 · Foundation and Higher
Melting 0.20 kg of ice already at 0 °C, with L = 334000 J/kg, requires 66800 J. Warming the resulting water to 20 °C, with c = 4200 J/(kg °C), needs 16800 J. Add the two stages: 83600 J. Do not use E = mcΔθ across the melting plateau. Cooling reverses these store changes; freezing/condensation release energy.
Misconception clinic
Read each belief, say what is wrong with it, then compare your correction.
Tempting idea: Temperature and average kinetic energy rise steadily.
Use instead: During the plateau average kinetic energy stays constant. Energy changes the particle potential energy/arrangement.
Tempting idea: E = mcΔθ.
Use instead: Δθ is zero during the ideal phase change. L is specific latent heat of vaporisation.
Retrieval practice
Explore the relationship
Use the energy position to locate a point on the heating curve. The heating rate then determines the time taken to supply that energy.
Model scope: 8463 and 8464 · Foundation and Higher
What to notice: use the readout to describe how one variable changes when the other is controlled.
Worked examples
Apply internal energy and temperature in the worked reasoning, then try the changed-context questions below.
Scope: 8463 and 8464 · Foundation and Higher
E = 5400 J.
Scope: 8463 and 8464 · Foundation and Higher
The energy changes particle arrangement and potential energy rather than average kinetic energy, so temperature remains constant. Ice’s open structure collapses during melting; universal separation is not the explanation.
Scope: 8463 Physics only · Higher only
Work done on the gas increases internal energy; temperature can rise.
Exam precision
Do this: Name whether temperature or state changes. Use E = mcΔθ or E = mL accordingly, and explain a plateau through potential-energy change rather than hotter particles.
Independent practice
Write an answer before opening the marking guidance. Then edit the exact phrase or step that would gain the next mark.
Scope: 8463 and 8464 · Foundation and Higher
Original PhysicsUK mark scheme: Point 1 (1 mark): E = mL. Point 2 (1 mark): E = 0.15 × 334000. Point 3 (1 mark): E = 50100 J (5.01 × 10⁴ J). Award each distinct point once. Accept equivalent scientifically correct wording. No half marks.
Model answer: E = mL. E = 0.15 × 334000. E = 50100 J (5.01 × 10⁴ J).
Acceptable answers: Expected result: E = 50100 J (5.01 × 10⁴ J). Accept the unrounded value or a correctly rounded equivalent to two or more significant figures; accept equivalent units if converted correctly. No additional measurement interval is implied.
Marking notes: Method marks remain available after an arithmetic error. Carry an earlier numerical error into a later valid step; award that method point if the unit conversion and physics are correct. A fully correct answer with unit earns all marks unless working is expressly requested.
Scope: 8463 and 8464 · Foundation and Higher
Original PhysicsUK mark scheme: Point 1 (1 mark): The temperature/average kinetic energy remains constant. Point 2 (1 mark): Energy increases particle potential energy as particles separate into a gas. Point 3 (1 mark): Internal energy increases despite the constant temperature. Award each distinct point once. Accept equivalent scientifically correct wording. No half marks.
Model answer: The temperature and average kinetic energy stay constant. Energy increases particle potential energy as the liquid becomes gas, so internal energy still rises.
Questions pupils ask
Yes. During a phase change, supplied energy changes particle potential energy while the mean kinetic energy and temperature remain constant.
Useful next steps