🎯 Common Question Types:
- State current atmospheric percentages (1–2 marks)
- Describe the evolution of the atmosphere (3–4 marks)
- Explain how photosynthesis changed the atmosphere (2–3 marks)
- Give evidence for early high CO₂ levels (2 marks)
- Name two ways CO₂ was removed from early atmosphere (2 marks)
📝 Key Command Words:
- State: Give the values (78% N₂, 21% O₂)
- Describe: Say what happened to CO₂ and O₂ levels over time
- Explain: Give the reason why (photosynthesis equation, solubility in oceans)
- Give evidence: Name specific evidence (limestone, fossil fuels, Venus/Mars comparison)
⚠️ Common Mistakes to Avoid:
- Mixing up early (mostly CO₂) with current atmosphere (mostly N₂)
- Forgetting cyanobacteria were the FIRST photosynthetic organisms
- Not mentioning BOTH oceans AND photosynthesis for CO₂ removal
- Forgetting that photosynthesis equation requires light energy as input
- Confusing CO₂ percentage: it is 0.04% NOT 0.4%
This exam tips covers Exam Tips for Atmosphere Composition within Composition of Atmosphere for GCSE Chemistry. Revise Composition of Atmosphere in Atmosphere for GCSE Chemistry with 20 exam-style questions and 12 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 12 of 13 in this topic. Treat this as a marking guide for what examiners are looking for, not just a fact list.
Practice questions for Composition of Atmosphere
What is the approximate percentage of nitrogen in the current atmosphere?
Describe how Earth's early atmosphere was formed.
Quick recall flashcards
What percentage of the atmosphere is CO₂?
About 0.04%
How was oxygen added to the atmosphere?
Photosynthesis by plants and algae