Environmental Chemistry
Chemistry environmental hub: air composition and pollutants, acid rain, greenhouse gases, global warming, and ozone depletion. Practise the topic with its check.
Before you begin
Maintaining air quality applies earlier chemistry to the atmosphere. The lessons move from air composition, pollutants and acid rain to the carbon cycle, climate change and the ozone layer.
Be comfortable with: fossil fuels (combustion and carbon dioxide emissions), oxides (acidic oxides and neutralisation) and rate of reaction (why a catalyst speeds up exhaust reactions).
Learning goals
- describe the volume composition of gases present in dry air as being approximately 78% nitrogen, 21% oxygen and the remainder being noble gases (with argon as the main constituent) and carbon dioxide
- name some common atmospheric pollutants, e.g. carbon monoxide; methane; nitrogen oxides (NO and NO2); ozone; sulfur dioxide; unburned hydrocarbons
- state the sources of these pollutants as — carbon monoxide from incomplete combustion of carbon-containing substances
- state the sources of these pollutants as — nitrogen oxides from lightning activity and internal combustion engines
- state the sources of these pollutants as — sulfur dioxide from volcanoes and combustion of fossil fuels
- describe the reactions used in possible solutions to the problems arising from some of the pollutants named in (b) — the redox reactions in catalytic converters to remove combustion pollutants (see also 10(d))
- describe the reactions used in possible solutions to the problems arising from some of the pollutants named in (b) — the use of calcium carbonate to reduce the effect of ‘acid rain’ and in flue gas desulfurisation
- discuss some of the effects of these pollutants on health and on the environment — the toxic nature of carbon monoxide
- discuss some of the effects of these pollutants on health and on the environment — the role of nitrogen dioxide and sulfur dioxide in the formation of ‘acid rain’ and its effects on respiration and buildings
- discuss the importance of the ozone layer and the problems involved with the depletion of ozone by reaction with chlorine-containing compounds, chlorofluorocarbons (CFCs)
- describe the carbon cycle in simple terms, to include — the processes of combustion, respiration and photosynthesis
- describe the carbon cycle in simple terms, to include — how the carbon cycle regulates the amount of carbon dioxide in the atmosphere (see also 11.1(d))
- state that carbon dioxide and methane are greenhouse gases and may contribute to global warming; give the sources of these gases and describe the potential effects of increased levels of these greenhouse gases, including more extreme weather events and melting of polar ice.
Lessons
Work through them in order.
Maintaining air quality
- Air Composition and EvidenceRead composition evidence and distinguish clean-air components from pollutants.
- Air Pollutants: Sources, Effects and ControlsBuild precise source–pollutant–effect chains and select targeted controls.
- Acid Rain Chemistry and ControlConnect acidic-oxide emissions to rainwater chemistry, effects and source control.
- Carbon CycleTrace carbon through combustion, respiration and photosynthesis.
- Greenhouse Effect, Climate and MitigationInterpret evidence and explain infrared heat trapping, consequences and responses.
- Ozone Layer and DepletionExplain ultraviolet protection, CFC-driven depletion and risk reduction.
Practise and check
Recommended nextMaintaining Air Quality topic check
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Topic reference
Common mistakes
- Clean-air composition is not a pollutant list.
- A source, an effect and a control are different parts of a causal answer.
- Acid rain, greenhouse warming and ozone depletion have different gases and mechanisms.