Chemistry of the atmosphere flashcards

Topic 9: Chemistry of the atmosphere

Composition of today's atmosphere

About 80% (four-fifths) nitrogen and about 20% (one-fifth) oxygen, with small amounts of carbon dioxide, water vapour and noble gases.

Earth's early atmosphere: where it came from and what it contained

Intense volcanic activity released mainly carbon dioxide and water vapour, with nitrogen; there was little or no oxygen. Water vapour condensed to form the oceans.

How did oxygen build up in the atmosphere?

Algae began photosynthesis about 2.7 billion years ago; then plants evolved, and oxygen rose over the next billion years until animals could evolve. 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

How did the amount of carbon dioxide decrease?

It dissolved in the oceans (carbonates precipitated), was used in photosynthesis, and was locked up in sedimentary rocks and fossil fuels.

How was limestone formed?

From the calcium carbonate shells and skeletons of sea creatures, compressed on the sea bed.

The greenhouse effect: name three greenhouse gases and describe how they warm the atmosphere

Water vapour, carbon dioxide, methane. The surface absorbs short wavelength radiation from the Sun and emits long wavelength (infrared) radiation; greenhouse gases absorb it and re-emit some back, so less energy escapes.

Two human activities that increase carbon dioxide, and two that increase methane

Carbon dioxide: burning fossil fuels, deforestation. Methane: cattle farming, rice paddy fields (also landfill waste decay).

Carbon footprint

The total amount of carbon dioxide and other greenhouse gases emitted over the full life cycle of a product, service or event.

Effects of carbon monoxide, sulfur dioxide, oxides of nitrogen and particulates

CO: toxic; colourless and odourless, so hard to detect. SO₂ and oxides of nitrogen: respiratory problems and acid rain. Particulates: global dimming and health problems.

Where does the nitrogen in oxides of nitrogen from a car engine come from?

From the air: nitrogen and oxygen react at the high temperature in the engine, not nitrogen in the fuel.