What does the Earth, atmosphere and resources module cover?

It draws together WJEC Unit 1 topics 1.3 (Water), 1.4 (The ever-changing Earth) and 1.6 (Limestone). It covers the water cycle, treating water and solubility, the composition of the atmosphere and how it evolved, the greenhouse effect, climate change and air pollution, and limestone, thermal decomposition and the limestone cycle.

Which unit and paper assess this module?

These topics are part of Unit 1 (Chemical substances, reactions and essential resources), assessed on the Unit 1 written paper. The paper is 1 hour 45 minutes, worth 80 marks and 45 percent of the qualification, sat at Foundation or Higher tier.

What are the key proportions and reactions to learn?

The atmosphere is about 78 percent nitrogen and 21 percent oxygen. Learn the thermal decomposition of calcium carbonate, the limestone cycle reactions, the water treatment stages, and the pollutant gases released when fuels burn.

How did the atmosphere change over time?

The early atmosphere was rich in volcanic carbon dioxide with little oxygen. As the Earth cooled the oceans formed and dissolved carbon dioxide, carbonate rocks locked more away, and photosynthesis by plants and algae removed carbon dioxide and released oxygen, giving today's atmosphere.

How should I revise this module?

Learn the atmosphere proportions and the story of how it evolved. Learn the water treatment stages and the test for water. Explain the greenhouse effect and the problems of carbon monoxide, sulfur dioxide and oxides of nitrogen. Memorise the limestone cycle and its four calcium compounds. Use WJEC past papers.

WalesChemistry

WJEC GCSE Chemistry: The Earth, atmosphere and resources (Units 1.3, 1.4, 1.6) overview

An overview of the Earth, atmosphere and resources module in WJEC GCSE Chemistry (topics 1.3, 1.4 and 1.6), mapping water and its treatment, the composition and evolution of the atmosphere, climate change and air quality, and limestone and its uses.

Generated by Claude Opus 4.87 min readWJEC Chemistry 1.3, 1.4, 1.6Updated 2026-06-14

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

Jump to a section

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

The Earth, atmosphere and resources module brings together WJEC Unit 1 topics 1.3, 1.4 and 1.6. It is about the essential resources the Earth provides - clean water, the air, and useful rock - and how human activity changes them. This page maps the module and links to a focused answer page for each part.

The topics in this module

Water treatment and solubility: The water cycle, treating water to make it safe, the test for water, and solubility. See Water treatment and solubility.
The Earth's atmosphere and its evolution: The composition of air today, the volcanic early atmosphere, and how carbon dioxide fell and oxygen rose. See The Earth's atmosphere and its evolution.
Climate change and air quality: Greenhouse gases and global warming, and the pollutant gases from burning fuels. See Climate change and air quality.
Limestone and its uses: Thermal decomposition of calcium carbonate, the limestone cycle, and building materials. See Limestone and its uses.

How this module fits the exam

These topics sit in Unit 1, assessed on the Unit 1 written paper (1 hour 45 minutes, 80 marks, 45%). Questions test the atmosphere proportions and its evolution, the greenhouse effect and pollutants, water treatment, and the reactions of the limestone cycle.

How to study this module

Learn the air. About 78 percent nitrogen, 21 percent oxygen, and how the atmosphere evolved.
Explain the greenhouse effect. Greenhouse gases trap heat; rising carbon dioxide warms the planet.
Match pollutants to problems. Carbon monoxide is toxic; sulfur dioxide and oxides of nitrogen cause acid rain.
Know water treatment. Filtration, sedimentation and chlorination, plus the test for water.
Master the limestone cycle. Carbonate to oxide to hydroxide to limewater and back to carbonate.

Then test yourself with the module quiz.

Sources & how we know this

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