Chemistry of the Atmosphere
Map Your Gaps
Card 1 of 10
Swipe right if you know it, left if you don't
✔ Know
✖ Don't know
Current atmospheric composition
The Earth's atmosphere today is a mixture of gases, dominated by nitrogen.
Students often guess oxygen is the most abundant — it isn't.
Current atmospheric composition — Key Knowledge
- Nitrogen ~78%
- Oxygen ~21%
- Argon ~1%
- Carbon dioxide ~0.04%
- Water vapour trace, variable
The early atmosphere
The Earth's early atmosphere was mainly carbon dioxide with little or no oxygen, similar to Mars and Venus today. Water vapour and other gases were released by volcanic activity.
The atmosphere changed dramatically over billions of years — it hasn't always been as it is now.
The early atmosphere — Key Knowledge
- Early atmosphere mainly CO₂, little/no O₂
- Volcanic activity released CO₂ and water vapour
How oxygen increased
Oxygen built up gradually as early algae and plants evolved and carried out photosynthesis over billions of years.
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
photosynthesis
Without photosynthesis, there would be no oxygen in the atmosphere.
How oxygen increased — Key Knowledge
- Photosynthesis produced oxygen
- Algae and plants first photosynthetic organisms
How carbon dioxide decreased
Carbon dioxide was removed from the early atmosphere by several processes over a long timescale.
Carbon that was once atmospheric CO₂ ended up trapped in rocks and fuels underground.
How carbon dioxide decreased — Key Knowledge
- Dissolved in oceans, Locked in sedimentary rocks e.g. limestone
- Stored in fossil fuels coal, oil, gas — formed from dead organisms
- Used by plants for photosynthesis
The greenhouse effect
Greenhouse gases absorb infrared radiation emitted by the Earth's surface and re-emit it in all directions, warming the atmosphere. This is a natural process that keeps Earth habitable.
The greenhouse effect itself is not bad — the problem is the enhanced greenhouse effect from human activity.
The greenhouse effect — Key Knowledge
- Greenhouse gases CO₂, methane, water vapour
- Infrared radiation absorbed and re-emitted by greenhouse gases
- Natural greenhouse effect essential for life on Earth
Human activities increasing greenhouse gases
Human activities are increasing the levels of greenhouse gases in the atmosphere, enhancing the greenhouse effect.
The enhanced greenhouse effect is caused by rising concentrations of greenhouse gases from these activities.
Human activities increasing greenhouse gases — Key Knowledge
- Burning fossil fuels releases CO₂
- Deforestation less CO₂ absorbed
- Agriculture and livestock methane from cattle and rice paddies
- Landfill methane from decomposing waste
Consequences of climate change
Rising greenhouse gas levels lead to global climate change with wide-ranging effects.
These consequences affect both human populations and the natural world.
Consequences of climate change — Key Knowledge
- Ice cap melting, Sea level rise, Extreme weather events floods, droughts, storms
- Loss of habitats and ecosystems, Changes to food production
Carbon footprint
The carbon footprint is the total amount of CO₂ and other greenhouse gases emitted over the full life cycle of a product, service or event.
It covers the entire life cycle — not just direct emissions from use.
Carbon footprint — Key Knowledge
- Carbon footprint total greenhouse gas emissions over full life cycle
- Reduction methods renewable energy, energy efficiency, carbon capture and storage, reducing waste
Pollutants from combustion
Burning fossil fuels releases several harmful pollutants alongside carbon dioxide.
Carbon monoxide is produced by incomplete combustion and is especially dangerous because it cannot be seen or smelled.
Pollutants from combustion — Key Knowledge
- Carbon monoxide toxic, colourless, odourless — binds to haemoglobin, prevents oxygen transport
- Sulfur dioxide causes acid rain
- Nitrogen oxides cause acid rain and photochemical smog
- Particulates/soot cause respiratory problems and global dimming
Acid rain and global dimming
Sulfur dioxide and nitrogen oxides dissolve in rainwater to form acid rain. Particulates reduce sunlight reaching the Earth's surface, causing global dimming.
These are distinct effects of atmospheric pollution, separate from the greenhouse effect.
Acid rain and global dimming — Key Knowledge
- Acid rain from SO₂ and NOₓ — damages buildings, harms aquatic life, kills plants
- Global dimming particulates reflect/block sunlight
Map your gaps
Chemistry of the Atmosphere
0%confident
✔
0
0
❓
0
0
✖
0
0