Question 1 Medium
A 250 cm³ sample of air is about 20% oxygen. Calculate the volume of oxygen.
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Answer: 50 cm³
- 20% of 250 = 0.20 × 250.
- 0.20 × 250 = 50 cm³.
The Earth's atmosphere, past and present: GCSE Combined Science Chemistry practice questions
A second set of questions on the Earth's atmosphere, past and present. They are different from the ones on the topic page. Try each, then open the answer and compare your working.
More questions
Question 2 Medium
About what percentage of the air today is carbon dioxide?
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Answer: 0.04%
- Carbon dioxide is a trace gas.
- It is about 0.04%.
Question 3 Hard
Which gas, released by volcanoes, built up in the air to make most of today's atmosphere?
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Answer: nitrogen
- Volcanoes released nitrogen too.
- It built up because it is unreactive.
Question 4 Hard
The Earth is about 4.6 billion years old. Algae first made oxygen about 2.7 billion years ago. How many billion years after the Earth formed was this?
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Answer: 1.9
- Subtract: 4.6 − 2.7.
- 4.6 − 2.7 = 1.9 billion years.
Question 5 Hard
Which two planets may have atmospheres like the Earth's early atmosphere?
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Answer: Mars and Venus
- Their atmospheres are mainly carbon dioxide.
- They are Mars and Venus.
Question 6 Hard
In air, 78% is nitrogen and 21% is oxygen. What percentage is neither nitrogen nor oxygen?
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Answer: 1%
- Add the two: 78 + 21 = 99.
- 100 − 99 = 1%.
Question 7 Hard
Limestone forms from the shells of sea creatures. What element in the shells came from carbon dioxide?
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Answer: carbon
- Calcium carbonate contains carbon.
- The carbon came from carbon dioxide that dissolved in the ocean.
Question 8 Hard
Name the type of fuel formed from the remains of tiny sea creatures that is a gas at room temperature.
Show answer
Answer: natural gas
- Crude oil and natural gas formed from tiny sea creatures.
- The one that is a gas is natural gas.
Quick checks
Short questions with options. Choose one before you open the answer.
Check 1
What percentage of today's air is nitrogen?
Show answer
About 80% (more exactly 78%).
Check 2
What percentage of today's air is oxygen?
Show answer
About 20% (more exactly 21%).
Check 3
Name three gases that make up a small part of today's air.
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Carbon dioxide, water vapour and noble gases such as argon.
Check 4
How was the early atmosphere formed?
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By gases released from intense volcanic activity.
Check 5
What was the main gas in the early atmosphere?
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Carbon dioxide.
Check 6
Which gas was missing or almost missing from the early atmosphere?
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Oxygen.
Check 7
Which two planets may have atmospheres like the early Earth?
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Mars and Venus.
Check 8
How did the oceans form?
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Water vapour condensed as the Earth cooled.
Check 9
What happened to carbon dioxide when the oceans formed?
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It dissolved in the water, and carbonates formed sediments.
Check 10
When did algae first produce oxygen?
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About 2.7 billion years ago.
Check 11
Which process produced oxygen in the atmosphere?
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Photosynthesis by algae and plants.
Check 12
What is the word equation for photosynthesis?
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Carbon dioxide + water → glucose + oxygen.
Check 13
Why did the percentage of oxygen gradually increase over a billion years?
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Plants evolved and photosynthesised, until there was enough oxygen for animals.
Check 14
How was limestone formed?
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From the shells and skeletons of sea creatures that built up on the sea floor.
Check 15
How was coal formed?
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From dead plants buried and squashed over millions of years.
Check 16
How were crude oil and natural gas formed?
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From the remains of tiny sea creatures buried under sediments and squashed over millions of years.
Check 17
Why is the evidence for the early atmosphere limited?
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It was 4.6 billion years ago, so there is little direct evidence.
Check 18
Why do theories about the early atmosphere change?
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New evidence can be found that does not fit the old theory.
Check 19
Name two ways carbon dioxide was removed from the early atmosphere.
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Dissolving in the oceans and photosynthesis (also locked in rocks and fossil fuels).
Check 20
What small amounts of gases may the early atmosphere have contained besides carbon dioxide?
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Water vapour, nitrogen, and small amounts of methane and ammonia.
Check 21
What percentage of today's air is carbon dioxide?
Show answer
About 0.04%.
Check 22
What is meant by precipitated carbonates?
Show answer
Carbonates that formed solids and settled out as sediments.
Check 23
How old is the Earth?
Show answer
About 4.6 billion years.
Check 24
What is a fossil fuel?
Show answer
A fuel formed from the remains of living things over millions of years, such as coal, oil and gas.
Keep going with The Earth's atmosphere, past and present
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