The Evolution of the AtmosphereAQA GCSE Chemistry: Flashcards

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What were the main gases in Earth's early atmosphere?

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What were the main gases in Earth's early atmosphere?: The early atmosphere consisted mainly of carbon dioxide and water vapour, with small amounts of ammonia and other gases. There was very little or no oxygen present.
Name the four main components of the current atmosphere and their approximate percentages.: Nitrogen (approximately 78%), oxygen (approximately 21%), argon (approximately 1%), and carbon dioxide and water vapour (small amounts).
Explain how water vapour changed the early atmosphere.: Water vapour in the early atmosphere condensed to form the oceans as the Earth cooled over billions of years.
How did carbon dioxide become locked away from the atmosphere?: Carbon dioxide dissolved in the oceans and became locked in sedimentary rocks and fossil fuels, removing it from the atmosphere.
What process produced oxygen in the atmosphere?: Photosynthesis by algae and plants produced oxygen, which accumulated in the atmosphere over billions of years.
Describe what happened to ammonia in the early atmosphere.: Ammonia was converted to nitrogen over billions of years, contributing to the development of the modern atmosphere.
For approximately how long has the atmosphere been broadly stable in composition?: The atmosphere has been broadly stable in composition for approximately 200 million years.
Why was there very little oxygen in the early atmosphere?: Because photosynthesis had not yet evolved to produce significant amounts of oxygen. Oxygen only accumulated after photosynthetic organisms appeared billions of years ago.
What was the main fate of carbon dioxide from the early atmosphere?: Carbon dioxide dissolved in the oceans and became locked in sedimentary rocks and fossil fuels, being removed from the atmosphere.
Name three ways the atmosphere changed over billions of years.: Water vapour condensed to form oceans; carbon dioxide dissolved and became locked in rocks and fossil fuels; photosynthesis produced oxygen; ammonia was converted to nitrogen.
What percentage of the current atmosphere is made up of nitrogen and oxygen combined?: Approximately 99% (nitrogen is approximately 78% and oxygen is approximately 21%).
Explain the relationship between ocean formation and atmospheric composition change.: As water vapour condensed to form the oceans, carbon dioxide dissolved into the water and was removed from the atmosphere, changing atmospheric composition significantly.
How did the evolution of photosynthetic life affect the atmosphere?: Photosynthesis by algae and plants produced oxygen, which accumulated in the atmosphere over billions of years, changing it from oxygen-poor to oxygen-rich.
What percentage of the atmosphere is argon in the current composition?: Approximately 1% of the atmosphere is argon.
Define the term 'broadly stable' in relation to atmospheric composition.: Broadly stable means that the composition of the atmosphere has remained approximately constant, showing only minor variations over approximately 200 million years.