What is the atmosphere made of, and how does burning fuels pollute it?
The composition of the atmosphere, the pollutants from burning fuels (carbon monoxide, sulfur dioxide, oxides of nitrogen, particulates), and the greenhouse effect and global warming.
A CCEA GCSE Chemistry answer on the atmosphere and pollution, covering the composition of the air, the pollutants released when fuels burn (carbon monoxide, sulfur dioxide, oxides of nitrogen and particulates) and their effects, and the greenhouse effect and global warming.
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What this dot point is asking
CCEA wants you to state the composition of the atmosphere, describe the pollutants released when fuels burn and the problems they cause, and explain the greenhouse effect and how it leads to global warming.
Composition of the atmosphere
These proportions have been roughly stable for a long time, but human activity is slowly increasing the carbon dioxide level, which has important effects on climate.
Pollutants from burning fuels
Carbon monoxide is dangerous because it combines with haemoglobin and stops the blood carrying oxygen. Acid rain from sulfur dioxide and oxides of nitrogen damages forests, lakes and limestone buildings.
The greenhouse effect and global warming
Worked example
Examples in context
Example 1. Cleaning up power stations. Power stations now remove sulfur dioxide from their waste gases (flue gas desulfurisation) to cut acid rain. The link between sulfur impurities and acid rain studied here directly drives this pollution-control technology.
Example 2. Cutting carbon emissions. Governments aim to reduce fossil fuel burning and switch to renewable energy to slow the rise in carbon dioxide. The connection between carbon dioxide, the greenhouse effect and global warming is the scientific basis for climate policy.
Try this
Q1. State the approximate percentages of nitrogen and oxygen in the atmosphere. [2 marks]
- Cue. Nitrogen about 78 percent; oxygen about 21 percent.
Q2. Name two greenhouse gases. [2 marks]
- Cue. Carbon dioxide and methane.
Exam-style practice questions
Practice questions written in the style of CCEA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
CCEA 20194 marksBurning fossil fuels releases sulfur dioxide and oxides of nitrogen. Explain how these gases form and one environmental problem they cause.Show worked answer →
Markers want the origin of each gas and an effect.
Sulfur dioxide forms because fossil fuels contain sulfur impurities that burn to form sulfur dioxide.
Oxides of nitrogen form when the high temperature of combustion (for example in a car engine) makes the nitrogen and oxygen in the air react together.
An environmental problem is acid rain: both gases dissolve in rainwater to form acids, and acid rain damages trees, kills aquatic life in lakes and corrodes buildings and statues made of limestone.
Markers reward sulfur impurities forming sulfur dioxide, high temperature making nitrogen and oxygen react to form oxides of nitrogen, and acid rain as a problem.
CCEA 20214 marksExplain how the greenhouse effect leads to global warming, naming two greenhouse gases and the main human activity that increases them.Show worked answer →
The marks are for the mechanism, the gases and the cause.
Greenhouse gases such as carbon dioxide and methane absorb the heat (infrared radiation) given off by the Earth and re-radiate some of it back to the surface, trapping heat in the atmosphere. This is the greenhouse effect.
Human activities, mainly the burning of fossil fuels (and deforestation), have increased the amount of carbon dioxide, enhancing the greenhouse effect. This traps more heat and causes global warming, leading to climate change.
Markers reward greenhouse gases absorbing and re-radiating the Earth's heat, naming carbon dioxide and methane, and burning fossil fuels as the main cause.
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Sources & how we know this
- CCEA GCSE Chemistry specification (1110) — CCEA (2017)