Chemistry C1 7.3 The Earth's atmosphere in the past.

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How was the Earth's early atmosphere formed?
By volcanic activity.
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What did the Earth's early atmosphere probably consist of?
Carbon dioxide, there may also have been water vapour together with traces of methane and ammonia.
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What happened to the atmosphere as plants spread over the Earth?
The levels of oxygen in the atmosphere increased.
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When do scientists think that the Earth was formed?
About 4.5 billion years ago.
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What do scientist believe the Earth was like in the first billion years?
Covered with volcanoes that released carbon dioxide, water vapour and nitrogen.
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What happened as the Earth cooled?
Most of the water vapour condensed to form the oceans, so the early atmosphere was mainly carbon dioxide with some water vapour, some scientists believe there was also nitrogen and possibly some methane and ammonia.
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What happened in the next two billion years?
Bacteria, algae and plants evolved.
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How did algae and plants change the Earth's atmosphere?
They used carbon dioxide for photosynthesis and this released oxygen. As the number of plants increased the amount of carbon dioxide in the atmosphere decreased and the amount of oxygen increased.
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Where did most of the carbon dioxide, nitrogen and water vapour in the Earth's early atmosphere come from?
Volcanoes.
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What produced the oxygen in the atmosphere?
Algae and plants (photosynthesis).
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**TRY TO MEMORISE THE MAIN GASES THAT WERE PROBABLY IN THE EARTH'S EARLY ATMOSPHERE**
**
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Card 2

Front

What did the Earth's early atmosphere probably consist of?

Back

Carbon dioxide, there may also have been water vapour together with traces of methane and ammonia.

Card 3

Front

What happened to the atmosphere as plants spread over the Earth?

Back

Preview of the front of card 3

Card 4

Front

When do scientists think that the Earth was formed?

Back

Preview of the front of card 4

Card 5

Front

What do scientist believe the Earth was like in the first billion years?

Back

Preview of the front of card 5
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