What does WJEC topic 1.8 Kinetic theory cover?

Topic 1.8 covers the particle model of solids, liquids and gases, density, changes of state and internal energy, gas pressure as the result of particle collisions, the link between temperature and particle speed, how pressure, volume and temperature are related, specific heat capacity, and specific latent heat of fusion and vaporisation.

Which equations do I need for kinetic theory?

The density equation (density equals mass over volume), the specific heat capacity equation (energy equals specific heat capacity times mass times temperature change), and the latent heat equation (energy equals mass times specific latent heat). The pressure equation (pressure equals force over area) also features. These appear on the WJEC formula list.

Which practicals appear in kinetic theory?

Measuring the density of regular and irregular solids and of liquids, and measuring the specific heat capacity of a material using an electric heater while recording the energy supplied and the temperature rise. These can be assessed in Unit 3 and sampled in the written papers.

How is kinetic theory examined?

It sits in Unit 1 (Electricity, Energy and Waves), a 1 hour 45 minute written paper worth 80 marks and 45% of the GCSE. Expect particle model explanations, density, specific heat and latent heat calculations, gas pressure reasoning, and interpretation of heating curves.

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WJEC GCSE Physics kinetic theory overview

An overview of topic 1.8 Kinetic theory in Unit 1 of WJEC GCSE Physics (3420), mapping the particle model and changes of state, gas pressure and temperature, and specific heat capacity and latent heat, with the key equations and how the topic is examined.

Generated by Claude Opus 4.87 min readWJEC 3420 Unit 1.8Updated 2026-06-14

Reviewed by: AI editorial process; not yet individually human-reviewed

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The topic 1.8 content
How topic 1.8 is examined
How to study topic 1.8
For the official specification

Topic 1.8 Kinetic theory of WJEC GCSE Physics (specification 3420) is about the particle model of matter, gas pressure, and the energy needed to change a substance's temperature or state. It is examined in Unit 1 (Electricity, Energy and Waves). This page maps the topic and links to a focused answer page for each part.

The topic 1.8 content

The particle model and changes of state: The arrangement of particles in solids, liquids and gases, density, changes of state as reversible physical changes, and internal energy. See The particle model and changes of state.
Gas pressure and temperature: Gas pressure from particle collisions, the link between temperature and particle speed, and how pressure, volume and temperature relate. See Gas pressure and temperature.
Specific heat capacity and latent heat: The specific heat capacity equation, specific latent heat of fusion and vaporisation, and why the temperature is constant during a change of state. See Specific heat capacity and latent heat.

How topic 1.8 is examined

Topic 1.8 sits in Unit 1, a written paper of 1 hour 45 minutes, worth 80 marks and 45% of the GCSE, tiered into Foundation and Higher. Expect particle model explanations, density and specific heat and latent heat calculations, gas pressure reasoning, and heating curve interpretation. A formula list is provided, and Higher candidates must rearrange equations.

How to study topic 1.8

Picture the particles. Know the arrangement, spacing and movement in each state, and use it to explain pressure and compression.
Choose the right equation. $E = cm\Delta\theta$ for temperature changes; $E = mL$ for state changes.
Use the temperature change. In $E = cm\Delta\theta$ , always use $\Delta\theta$ , not the final temperature.
Read heating curves. Flat sections are changes of state, where energy breaks bonds rather than raising the temperature.
Keep units consistent. Mass in kilograms for the energy equations; match density units.

For the official specification

WJEC publishes the full specification, past papers and mark schemes at wjec.co.uk. Always revise from the current specification and WJEC's own past papers, because question style, tiering and the formula list are board-specific.

Sources & how we know this

WJEC GCSE Physics specification (3420) from 2016 — WJEC (2016)