AQA · Chemistry · 8462
GCSE Chemistry (AQA): The Evolution of the Atmosphere
Topic 8 — Chemical Analysis. Generated from the caption track of Cognito's lesson video "GCSE Chemistry - Evolution of the Atmosphere | How the Atmosphere Changed Over Time (2027/28 exams)"; each card deep-links to the moment in the video it came from. Lesson 9.01 of Cognito's AQA GCSE Combined Science (Trilogy) and Chemistry course (Higher tier), filed under AQA Chemistry 8462. Teaching by Cognito — https://cognitoedu.org/coursesubtopic/c2-gcse-aqa-h-c_9.01.
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Crude oil and natural gas formed mainly from the remains of which organisms?
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Plankton — tiny organisms that float in the ocean.
How did Earth's oceans form?
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Water vapour in the early atmosphere condensed into liquid water as the Earth cooled.
Coal is a sedimentary rock formed from thick deposits of dead ? material.
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plant
How did the formation of the oceans reduce atmospheric carbon dioxide?
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CO₂ dissolved in the ocean water, forming carbonate precipitates that became sediments on the seabed.
What is the approximate composition of Earth's atmosphere today?
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About 80% nitrogen and 20% oxygen, with all other gases (CO₂, water vapour, noble gases) under 1%.
What produced the gases of Earth's early atmosphere?
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Intense volcanic activity during the first billion years.
What is limestone mostly made from?
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Calcium carbonate from the shells and skeletons of marine organisms.
Why did rising atmospheric oxygen matter for life on Earth?
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It allowed more complex organisms such as animals to evolve.
The early atmosphere was mostly ?, much like the atmospheres of Mars and Venus today.
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carbon dioxide
Which two gases were released by early volcanoes in only small amounts?
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Methane and ammonia.
How long ago did algae first appear and begin producing oxygen?
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About 2.7 billion years ago.
How did dead organisms lock carbon out of the atmosphere?
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They sank to the seabed, were buried in sediment and compressed over millions of years into sedimentary rock, oil and gas.
Which process caused oxygen levels in the atmosphere to rise?
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Photosynthesis by algae and green plants, which takes in CO₂ and releases oxygen.
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