Skip to main content
WalesChemistrySyllabus dot point

How do human activities change the climate and the quality of the air we breathe?

Greenhouse gases and climate change, the combustion products that pollute the air, and the problems each pollutant causes.

A focused answer to WJEC GCSE Chemistry topic 1.4 on climate change and air quality, covering greenhouse gases and global warming, the gases released when fuels burn, and the environmental problems caused by carbon monoxide, sulfur dioxide and oxides of nitrogen.

Generated by Claude Opus 4.89 min answer

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

Have a quick question? Jump to the Q&A page

Jump to a section
  1. What this topic is asking
  2. The greenhouse effect and climate change
  3. Products of combustion
  4. The pollutants and their problems
  5. Try this

What this topic is asking

WJEC wants you to explain how greenhouse gases cause climate change and to identify the pollutants released when fuels burn and the problems they cause. This is part of topic 1.4 The ever-changing Earth in Unit 1 of WJEC GCSE Chemistry (3430).

The greenhouse effect and climate change

Products of combustion

Carbon dioxide and water themselves are not air pollutants in the toxic sense, but carbon dioxide is the main greenhouse gas of concern, so even a perfectly clean-burning fossil fuel still contributes to climate change. This is why reducing emissions involves both burning fuels more completely (to cut carbon monoxide and soot) and, more importantly, burning fewer carbon fuels overall.

The pollutants and their problems

Some of these problems can be reduced. Removing sulfur from fuels before they are burned, and using flue-gas desulfurisation to scrub sulfur dioxide out of power-station chimneys, both cut acid rain. Catalytic converters fitted to cars convert carbon monoxide and oxides of nitrogen into less harmful carbon dioxide and nitrogen. These measures lower the local pollutants that harm health, but they do not remove the carbon dioxide that drives climate change.

Try this

Q1. Name the toxic gas formed by the incomplete combustion of a fuel. [1 mark]

  • Cue. Carbon monoxide.

Q2. State one environmental problem caused by sulfur dioxide. [1 mark]

  • Cue. It causes acid rain, which damages trees, lakes and buildings.

Exam-style practice questions

Practice questions written in the style of WJEC exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.

WJEC 20203 marksExplain how the burning of fossil fuels can lead to global warming.
Show worked answer →

A topic 1.4 Explain question. Burning fossil fuels releases carbon dioxide, a greenhouse gas (1 mark). Greenhouse gases absorb the heat (infrared) radiated from the Earth's surface and re-emit some of it back, trapping energy in the atmosphere (1 mark). As the concentration of carbon dioxide rises, more heat is trapped, so the average global temperature increases - global warming, a form of climate change (1 mark). Markers reward naming carbon dioxide as a greenhouse gas, the trapping of heat, and the link to rising temperature. A common error is to confuse the greenhouse effect with the hole in the ozone layer.

WJEC 20234 marksName two pollutant gases produced when a fuel burns in a car engine and state one problem caused by each.
Show worked answer →

A topic 1.4 structured question. Carbon monoxide is produced by incomplete combustion; it is a toxic gas that reduces the blood's ability to carry oxygen (2 marks for gas and problem). Oxides of nitrogen form at the high temperature in the engine; they cause acid rain and respiratory problems/photochemical smog (2 marks for gas and problem). Sulfur dioxide (acid rain) is an acceptable alternative if a sulfur-containing fuel is used. Markers reward two pollutant gases each paired with a correct problem. A common error is to give carbon dioxide, which is a greenhouse gas rather than a toxic pollutant here.

Related dot points

Sources & how we know this