Describe matter with particles
A solid has particles in fixed positions, a liquid has particles that move past one another, and a gas has particles far apart moving randomly. The particles themselves do not expand when a substance is heated.
GCSE Physics resources
AQA GCSE Particle model of matter
AQA GCSE Particle model of matter Revision
Use a particle model to explain density, changes of state, internal energy and gas pressure. Keep particle spacing, particle motion and energy separate.
Topic overview
Plan your particle model of matter revision
Use the resource cards below to revise one idea at a time. Each page includes worked examples, mini quizzes, practice questions, exam language and a visual or simulation when it adds learning value.
Knowledge map
How the topic fits together
Use this overview to find the part of the topic that needs attention; the focused guides below teach and assess each idea in depth.
Link temperature to energy
Heating changes the internal energy of a system. During a change of state, energy changes the separation of particles while the temperature remains constant for a pure substance.
Explain pressure with collisions
Gas pressure comes from particles colliding with the container walls. Increasing temperature increases average kinetic energy; compressing a fixed mass increases collision frequency.
Focused revision
Choose one idea at a time
Each guide combines explanation, a diagnostic check, misconception repair, worked examples and exam-style practice.
PM-01
Density and Particle Arrangement
Dense materials pack more mass into each unit of volume. Use mass and volume measurements with consistent units, and explain changes in density using particle spacing rather than saying particles themselves become heavier.
PM-02
Internal Energy and Heating Curves
Internal energy is the total kinetic and potential energy of the particles. Sloped sections of a heating curve show increasing average kinetic energy; flat sections show a change of state while separation changes.
PM-03
Gas Pressure and Temperature
In a sealed rigid container, heating increases particle speed and collision force/frequency, so pressure rises. Compressing a gas increases collision frequency with the walls when temperature is constant.
PM-04
Density Required Practical
Measure mass with a balance. For a regular object, calculate volume from dimensions; for an irregular object, use water displacement. Read scales at eye level and remove trapped air bubbles.
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