This memory aid covers Memory Aid 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 10 of 13 in this topic. Use it for quick recall, then test yourself straight afterwards so the memory aid becomes usable in an answer.
🧠 Memory Aid
78-21-1: Nitrogen-Oxygen-Argon (NOA)
For atmospheric evolution, remember the sequence: "Volcanoes → Oceans → Algae → Life → Stability"
For what removed CO₂: "POLS" — Photosynthesis, Oceans (dissolved), Limestone (carbonate rocks), Sediment (fossil fuels)
Quick Check: Give TWO reasons why CO₂ decreased from the early atmosphere to present levels.
1. CO₂ dissolved in the oceans and reacted with minerals to form carbonate rocks (limestone). 2. Photosynthesis by cyanobacteria and plants converted CO₂ to glucose and oxygen.
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.