Three routes removed carbon dioxide
Three routes removed carbon dioxide

Earth's early atmosphere was rich in carbon dioxide, CO2\text{CO}_2CO2. Its proportion fell because carbon was transferred from the atmosphere into living organisms, the oceans, rocks and fossil fuels.
Step-by-step lessons on AQA GCSE Chemistry 9.1.4 How carbon dioxide decreased. 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.