Curriculum Portal

neurologyYou need to know

• The current atmosphere is about 78% nitrogen, 21% oxygen, 0.04% carbon dioxide, and small proportions of argon, water vapour and other gases.
• Earth’s early atmosphere about 4.6 billion years ago was mainly carbon dioxide and water vapour, with little or no oxygen.
• The early atmosphere also contained smaller amounts of nitrogen, methane and ammonia released by volcanic activity.
• Water vapour in the early atmosphere condensed as the Earth cooled, forming oceans and removing large amounts of water vapour from the atmosphere.
• Carbon dioxide levels decreased over time because carbon dioxide dissolved in oceans and became locked into carbonate rocks such as limestone.
• Carbon dioxide was also removed from the atmosphere by photosynthesis, which uses carbon dioxide and releases oxygen.
• Oxygen levels increased over time because algae and plants carried out photosynthesis for millions of years.
• Crude oil and natural gas formed from buried remains of marine organisms, so some carbon from the atmosphere became stored in fossil fuels.
• Limestone formed from the shells and skeletons of marine organisms containing carbonates, so some carbon became stored in sedimentary rock.
• The greenhouse effect happens when greenhouse gases absorb infrared radiation emitted from Earth’s surface and re-radiate it, keeping the planet warmer.
• The natural greenhouse effect is essential because it helps maintain temperatures on Earth that can support life.
• Important greenhouse gases include carbon dioxide, methane, water vapour and nitrous oxide.
• Short-wavelength radiation from the Sun passes through the atmosphere more easily than long-wavelength infrared radiation emitted by the Earth.
• Human activities increasing greenhouse gases include burning fossil fuels, deforestation, farming livestock, rice cultivation and landfill waste.
• Increasing concentrations of greenhouse gases are linked to global warming and climate change.
• Evidence for climate change can be difficult to evaluate because climate data vary naturally, come from different sources and are interpreted using complex models.
• Potential effects of global climate change include rising sea levels, more extreme weather, changing rainfall patterns, loss of habitats, reduced biodiversity and impacts on food production.
• Common atmospheric pollutants include carbon monoxide, soot or carbon particulates, sulphur dioxide and oxides of nitrogen.
• Carbon monoxide and soot are produced during incomplete combustion of fuels, especially when there is not enough oxygen for complete combustion.
• Sulphur dioxide is produced when fuels containing sulphur impurities burn, and oxides of nitrogen form when nitrogen and oxygen in the air react at high temperatures in engines and power stations.

• Calculate the percentage composition of gases in the atmosphere using given data and compare it with the accepted values for the modern atmosphere.
• Explain changes in atmospheric carbon dioxide and oxygen over time by linking dissolving in oceans, formation of carbonate rocks, fossil fuel formation and photosynthesis.
• Use word equations to predict combustion products from a fuel’s composition, including carbon dioxide and water for complete combustion of hydrocarbons.
• Predict when incomplete combustion may produce carbon monoxide and carbon particulates, especially when oxygen supply is limited.
• Explain the greenhouse effect using the ideas of short-wavelength solar radiation, long-wavelength infrared radiation, absorption and re-radiation by greenhouse gases.
• Evaluate evidence for global climate change by considering trends, reliability of data, natural variation and limitations of climate models.
• Discuss the scale, risk and environmental implications of climate change using specific examples such as sea-level rise, extreme weather and ecosystem disruption.
• Describe how pollutants from burning fuels cause problems, linking carbon monoxide to toxic effects, soot to respiratory problems and global dimming, and sulphur dioxide and nitrogen oxides to acid rain.
• Define the carbon footprint of a product as the total amount of carbon dioxide and other greenhouse gases emitted over its full life cycle.
• Suggest actions to reduce carbon dioxide and methane emissions, such as using renewable energy, improving energy efficiency, reducing waste, changing farming practices and protecting forests, while explaining why impacts may be limited by cost, technology or behaviour.