This exam focus covers Exam Focus 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 less often, but it can still be a useful differentiator on mixed-topic papers. It is section 11 of 13 in this topic. Treat this as a marking guide for what examiners are looking for, not just a fact list.
Topic position
Section 11 of 13
Practice
20 questions
Recall
12 flashcards
🎯 Exam Focus
High Frequency
What Examiners Ask About Atmosphere Composition
- "State the approximate proportions of nitrogen and oxygen in the atmosphere" — 78% nitrogen, 21% oxygen (1 mark)
- "Describe how the atmosphere changed from Earth's early history to today" — decrease in CO₂, increase in O₂ due to photosynthesis (3–4 marks)
- "Explain how photosynthesis changed the atmosphere" — plants removed CO₂, released O₂ (2–3 marks)
- "Why is there evidence that the early atmosphere had high CO₂ levels?" — limestone deposits, comparison with Venus/Mars (2 marks)
- "Give two ways CO₂ was removed from the early atmosphere" — dissolved in oceans/photosynthesis (2 marks)