GCSE›Edexcel GCSE Chemistry›Mind mapsEarth & Atmospheric ScienceEdexcel GCSE Chemistry: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsEarly atmosphereCame from volcanic activityMostly CO₂ and water vapourLittle or no oxygenEvidence is inferred from volcanoes todayOceans and CO₂Water vapour condensed to form oceansCO₂ dissolved into the oceansLocked in limestone and fossil fuelsOxygen builds upAlgae and plants evolved 2.7 billion years ago6 COX2+6 HX2O→CX6HX12OX6+6 OX2\ce{6CO2 + 6H2O -> C6H12O6 + 6O2}6COX2+6HX2OCX6HX12OX6+6OX2Photosynthesis removed CO₂Oxygen test: glowing splint relightsAtmosphereEarth and climateN₂O₂CO₂Today's air80% nitrogen20% oxygenUnder 1% CO₂, argon and othersGreenhouse effectCO₂, methane, water vapourAbsorb heat radiated by EarthRe-release it in all directionsBurning fossil fuels releases CO₂Livestock farming releases methaneExam tipsEvaluate: give the correlation and an uncertaintySay absorb and re-release, not 'trap'Correlation does not prove causation