AQA · GCSE · Chemistry
Course version: 8462 · Version from Sept 2018
At the start of this period the Earth’s atmosphere may have been like the…
Full specification wording
The Earth's early atmosphere: At the start of this period the Earth’s atmosphere may have been like the atmospheres of Mars and Venus today, consisting of mainly carbon dioxide with little or no oxygen gas.
This statement compares the Earth’s early atmosphere with the present-day atmospheres of Mars and Venus.
Checked against the AQA 8462 specification (opens in a new tab) on .
- Point 4 of 7
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
This statement compares the Earth’s early atmosphere with the present-day atmospheres of Mars and Venus. At the start of the first billion years, the Earth’s atmosphere is thought to have been mainly carbon dioxide, with little or no oxygen. Mars and Venus today have atmospheres dominated by carbon dioxide and contain almost no oxygen, so they provide a useful model for the early Earth. The word ‘may’ shows this is a theory based on evidence, not a directly observed fact. A good way to remember the composition is: early Earth atmosphere = mainly carbon dioxide + little or no oxygen. This contrasts with today’s atmosphere, which is about four-fifths nitrogen and one-fifth oxygen, with small amounts of other gases.
What earns the marks
- States that the early Earth’s atmosphere was mainly carbon dioxide.
- States that there was little or no oxygen in the early atmosphere.
- Compares the early Earth’s atmosphere with those of Mars and Venus today.
- Recognises that this is a theory or suggestion, not a certainty.
- Contrasts the early atmosphere with the present-day atmosphere of Earth.
Common mistakes and how to put them right
Saying the early atmosphere was mainly oxygen.
Put it right: Oxygen only increased later, after photosynthesis by plants and algae.
Writing that the early atmosphere contained no carbon dioxide.
Put it right: It was mainly carbon dioxide.
Exam tips
- Use the phrase ‘mainly carbon dioxide’ rather than ‘lots of carbon dioxide’ to match scientific precision.
- When comparing with Mars and Venus, mention both carbon dioxide and the lack of oxygen.
- If the question says ‘may have been’, include the idea of a theory or suggestion in your answer.
Try the lesson
The start of the The Earth's early atmosphere: At the start of this period the Earth’s atmosphere may have been like the atmospheres of Mars and Venus today, consisting of mainly carbon dioxide with little or no oxygen gas. lesson, made from checked teaching notes for this specification point.
Have a go first
Which gas is thought to have made up the majority of the Earth's early atmosphere?
Listen
This statement compares the Earth’s early atmosphere with the present-day atmospheres of Mars and Venus. At the start of the first billion years, the Earth’s atmosphere is thought to have been mainly carbon dioxide, with little or no oxygen. Mars and Venus today have atmospheres dominated by carbon dioxide and contain almost no oxygen, so they provide a useful model for the early Earth. The word ‘may’ shows this is a theory based on evidence, not a directly observed fact. A good way to remember the composition is: early Earth atmosphere = mainly carbon dioxide + little or no oxygen. This contrasts with today’s atmosphere, which is about four-fifths nitrogen and one-fifth oxygen, with small amounts of other gases. A strong answer earns marks for these points. States that the early Earth’s atmosphere was mainly carbon dioxide. States that there was little or no oxygen in the early atmosphere. Compares the early Earth’s atmosphere with those of Mars and Venus today. Recognises that this is a theory or suggestion, not a certainty. Exam tip: Use the phrase ‘mainly carbon dioxide’ rather than ‘lots of carbon dioxide’ to match scientific precision.
Key words
Say what each word means before you turn the card.
Composition of the early atmosphere
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Comparison with Mars and Venus
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Role of carbon dioxide
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Absence of oxygen
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See every definition
- Composition of the early atmosphere
- The Earth's atmosphere at the start of this period may have consisted of mainly carbon dioxide with little or no oxygen gas.
- Comparison with Mars and Venus
- The Earth's early atmosphere may have been like the atmospheres of Mars and Venus today, which provide a useful model for the early Earth.
- Role of carbon dioxide
- Carbon dioxide was the main gas in the Earth's early atmosphere, and the atmospheres of Mars and Venus today are dominated by carbon dioxide.
- Absence of oxygen
- There was little or no oxygen gas in the early atmosphere, and the atmospheres of Mars and Venus today contain almost no oxygen.
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