A changing atmosphere
A changing atmosphere
The early atmosphere contained a great deal of water vapour and carbon dioxide, but almost no oxygen. Cooling, ocean formation and the appearance of photosynthetic organisms gradually changed this composition.
Step-by-step lessons on Edexcel GCSE Chemistry 9.2.2 How the atmosphere evolved. Each one builds up to exam-style questions. Nail the core quantitative topics — moles, balancing equations and calculations — early on, since they underpin higher-tier questions across every paper and topic.