Summary AQA GCSE Chemistry Combined Science - Chemistry of the Atmosphere Notes

CHEMISTRY OF THE ATMOSPHERE

THE COMPOSITION AND EVOLUTION OF THE EARTH’S
ATMOSPHERE
THE EARTH’S EARLY ATMOSPHERE
 The main gases in the Earth’s early atmosphere were carbon dioxide, water vapour and
nitrogen, with some methane and ammonia
o These gases were released by volcanic activity
 As the Earth cooled:
o Water vapour condensed to form oceans and water to fall as rain
o Some carbon dioxide in the atmosphere dissolved in the oceans, forming carbonates




HOW OXYGEN INCREASED
 Algae and plants increased the amount of oxygen
 Algae first produced oxygen about 2.7 billion years ago
 As the atmosphere became richer in oxygen, animals were able to evolve




HOW CARBON DIOXIDE DECREASED
 The carbon dioxide in the atmosphere has decreased due to bacteria and algae




CARBON DIOXIDE AND METHANE AS GREENHOUSE
GASES
GREENHOUSE GASES
 Greenhouse gases: carbon dioxide, methane, water vapour
 Greenhouse effect:
o As energy from the sun reaches earth, short wave electromagnetic radiation passes
through the atmosphere
o Some is absorbed by Earth, but some is reflected
o Some reflected radiation is absorbed by greenhouse gases
o This causes the bonds in their molecules to bend and stretch