Topic 9: Chemistry of the Atmosphere

What are the main gases in Earth’s current atmosphere?

~80% nitrogen, ~20% oxygen, small amounts of CO₂, water vapour, and noble gases.

What was Earth’s early atmosphere like?

Mostly CO₂, with little/no O₂, and some nitrogen, methane, and ammonia.

What caused the formation of Earth’s early atmosphere?

Volcanic activity released gases like CO₂, water vapour, and nitrogen.

How did oceans reduce CO₂ levels?

CO₂ dissolved in oceans and formed carbonate sediments.

How did oxygen levels increase?

Algae and plants produced oxygen via photosynthesis.

How did CO₂ levels decrease over time?

Photosynthesis, formation of sedimentary rocks, and fossil fuels.

Name three greenhouse gases.

Water vapour, carbon dioxide, methane.

What is the greenhouse effect?

Greenhouse gases absorb infrared radiation from Earth, warming the atmosphere.

Name human activities that increase greenhouse gases.

Driving cars, using electricity, landfill decay (CH₄), raising livestock (CH₄).

What is global climate change?

Long-term shifts in weather patterns due to increased global temperatures.

Give two effects of climate change.

Rising sea levels, extinction of species, migration, lower crop yields.

What is a carbon footprint?

Total amount of CO₂ and greenhouse gases emitted over a product’s life cycle.

How can we reduce the carbon footprint?

Use less electricity, drive less, plant trees.

Why is reducing carbon footprints difficult?

Cost, lack of alternatives, lifestyle changes, land use issues.

What are the products of complete combustion?

Carbon dioxide and water.

What causes incomplete combustion?

Not enough oxygen; produces carbon monoxide, soot, and unburnt fuels.

Name pollutants formed when fuels are burned.

CO₂, H₂O, CO, NOₓ, SO₂, particulates.

What are the dangers of carbon monoxide?

It is toxic, colourless, odourless – binds to haemoglobin, reducing oxygen transport.

What do sulfur dioxide and nitrogen oxides cause?

Acid rain and respiratory problems.

What are the effects of particulates?

Cause global dimming and respiratory health issues.