Separate Chemistry - C9 Chemistry of the Atmosphere Flashcards
For approximately how many years have the proportion of gases in the atmosphere stayed the same?
200 million years
What are the approximate proportions of nitrogen and oxygen in our atmosphere (as a fraction and percentage).
- Nitrogen (4/5 or 80%)
- Oxygen (1/5 or 20%)
Other than Nitrogen and Oxygen, name some gases that are present in very small quantities in our atmosphere.
- Water vapour
- Noble gases
- Carbon dioxide
Why is there only limited evidence of what the early atmosphere was like and how it evolved?
Because there is such a large timescale (4.6 billion years).
One theory suggest that the Earth’s early atmosphere was shaped by intense volcanic activity.
a) Name the planets that have similar atmospheric conditions to those described by this theory.
b) What was the main gas present in the atmosphere at this time?
a) Mars and Venus
b) Carbon dioxide
How do most scientists believe the oceans were formed?
Water vapour in the early atmosphere condensed to form the oceans
Describe the composition of gases in the early atmosphere.
- Mainly carbon dioxide
- With small amounts of methane and ammonia
How did the amount of carbon dioxide in the early atmosphere reduce?
- Dissolved in the oceans
- Locked up in sedimentary rocks (carbonate precipitate forming sediment)
- Locked up in fossil fuels (calcium carbonate shells of marine organisms)
Write a word and balanced symbol equation for photosynthesis.
carbon dioxide + water → glucose + oxygen
6CO2 + 6H2O → C6H12O6 + 6O2
Describe how the oxygen levels in the early atmosphere increased?
- Algae produced oxygen by photosynthesis 2.7 billion years ago.
- Over the next billion years, plants evolved and produced oxygen by photosynthesis.
As well as increasing oxygen levels, what other effect did algae and plants have on the atmosphere?
Reduced carbon dioxide in the atmosphere (by photosynthesising)
Describe how limestone is formed
- Dead marine organisms fall to the bottom of the sea.
- Their calcium carbonate shells and skeletons are compressed over millions of years.
- Calcium carbonate rock (limestone) is formed. This is a sedimentary rock.
Describe how coal is formed.
- Plant deposits fall to the bottom of the sea.
- The plant deposits are covered by layers of sediment.
- Over millions of years, the plant deposits are compressed and coal is formed.
Describe how crude oil is formed.
- Deposits of dead plankton collect at the bottom of the sea.
- They become buried by layers of sediment and are compressed over millions of years.
- Crude oil and natural gas are then formed and are found as resevoirs deep underground.
Describe how natural gas is formed.
- Deposits of dead plankton collect at the bottom of the sea.
- They become buried by layers of sediment and are compressed over millions of years.
- Crude oil and natural gas are then formed and are found as resevoirs deep underground.