What does the Rates, energy and equilibria module cover?

This module gathers three WJEC topics: 1.5 (rate of chemical change), 2.4 (chemical reactions and energy) and 2.6 (reversible reactions and industrial processes). It covers how rate is measured and explained by collision theory, the factors that change rate, exothermic and endothermic reactions and reaction profiles, bond energy calculations, dynamic equilibrium and Le Chatelier's principle, and the Haber and Contact industrial processes.

Which units and papers assess this module?

Topic 1.5 is in Unit 1 and topics 2.4 and 2.6 are in Unit 2, so this module spans both written papers. Each paper is 1 hour 45 minutes, worth 80 marks and 45 percent of the qualification, sat at Foundation or Higher tier.

What maths skills are needed here?

You calculate average rates from graphs or data, read activation energy and overall energy change from reaction profiles, and (at Higher) calculate overall energy changes from bond energies using bonds broken minus bonds made.

What is the most important idea in this module?

Collision theory ties most of it together: rate depends on the frequency and energy of successful collisions. Energy changes come from breaking and making bonds, and Le Chatelier's principle predicts how equilibria shift. The Haber and Contact processes apply all of these to industry.

How should I revise this module?

Learn collision theory and use it to explain every rate factor. Practise drawing and reading reaction profiles, and bond energy calculations. Memorise dynamic equilibrium and the three Le Chatelier rules (temperature, concentration, pressure). Learn the Haber and Contact conditions and the compromise argument. Use WJEC past papers and watch command words like Explain and Calculate.

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WJEC GCSE Chemistry: Rates, energy and equilibria (Unit 1.5, 2.4, 2.6) overview

An overview of the Rates, energy and equilibria module in WJEC GCSE Chemistry, mapping topics 1.5, 2.4 and 2.6: rate of reaction and collision theory, factors affecting rate and catalysts, energy changes and reaction profiles, bond energy calculations, reversible reactions and equilibrium, and the Haber and Contact processes.

Generated by Claude Opus 4.87 min readWJEC Chemistry 1.5, 2.4, 2.6Updated 2026-06-14

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

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The topics in this module
How this module fits the exam
How to study this module

The Rates, energy and equilibria module gathers three closely linked WJEC topics: 1.5 (rate of chemical change), 2.4 (chemical reactions and energy) and 2.6 (reversible reactions and industrial processes). Together they explain how fast reactions go, how much energy they transfer, and how reversible reactions reach a balance - and then apply all of this to two major industrial processes. This page maps the module and links to a focused answer page for each part.

The topics in this module

Rates of reaction and collision theory: What rate means, how to measure it, reading rate graphs, and collision theory with activation energy. See Rates of reaction and collision theory.
Factors affecting rate and catalysts: How temperature, concentration or pressure, surface area and catalysts change the rate, all explained by collision theory. See Factors affecting rate and catalysts.
Energy changes and reaction profiles: Exothermic and endothermic reactions, drawing and reading reaction profiles, activation energy and overall energy change. See Energy changes and reaction profiles.
Bond energy calculations: Why breaking bonds is endothermic and making them exothermic, and calculating energy changes from bond energies. See Bond energy calculations.
Reversible reactions and equilibrium: Reversible reactions, dynamic equilibrium and Le Chatelier's principle for temperature, concentration and pressure. See Reversible reactions and equilibrium.
The Haber and Contact processes: Making ammonia and sulfuric acid, the conditions used, fertilisers, and the compromise between yield, rate and cost. See The Haber and Contact processes.

How this module fits the exam

These topics span Unit 1 (1.5) and Unit 2 (2.4, 2.6), so they appear on both written papers (each 1 hour 45 minutes, 80 marks, 45%). Questions mix explanation (collision theory, Le Chatelier) with calculation (rates, bond energies).

How to study this module

Master collision theory. Use it to explain every rate factor.
Practise rate graphs. Steepness equals rate; flat means finished.
Draw reaction profiles. Exothermic products low, endothermic products high, with activation energy.
Drill bond energy sums. Bonds broken minus bonds made; negative is exothermic.
Learn the equilibrium rules. Le Chatelier for temperature, concentration and pressure, then apply to the Haber and Contact processes.

Then test yourself with the module quiz.

Sources & how we know this

WJEC GCSE Chemistry specification (from 2016) — WJEC (2016)