The composition of the Earth's atmosphere has changed dramatically over its 4.6-billion-year history.
Which row in the table correctly identifies the relative abundance of carbon dioxide (CO2\text{CO}_2CO2) in the Earth's early atmosphere, the overall trend in its atmospheric concentration over geological time to today, and a key process that drove this trend?
| Relative abundance in the early atmosphere | Overall trend to today | Key process driving this trend | |
|---|---|---|---|
| A | Trace component (<1%) | Decreased | Dissolution in oceans and condensation of water vapour |
| B | Major component (>90%) | Decreased | Photosynthesis and carbonate rock formation |
| C | Major component (>90%) | Increased | Volcanic outgassing and respiration |
| D | Trace component (<1%) | Increased | Combustion of fossil fuels and deforestation |
A Row A B Row B C Row C D Row D
Row A
Row B
Row C
Row D
97 exam-style questions on Edexcel GCSE Chemistry 9.2 Earth and atmospheric science, covering 9.2.1 The Earth's early atmosphere, 9.2.2 How the atmosphere evolved, 9.2.3 Chemical test for oxygen, and 9.2.4 The greenhouse effect and climate change. Each one has a worked solution and a mark scheme showing where the marks go.