OCR GCSE Chemistry A C6.3 Interpreting and Interacting with Earth Systems Exam Questions

About OCR GCSE Chemistry A C6.3 Interpreting and Interacting with Earth Systems

C6.3 completes the OCR Gateway Chemistry A course by looking at how the Earth's atmosphere formed, how human activity changes it and how safe drinking water is produced. It is part of Topic C6 Global challenges, assessed in Paper 2 (Foundation) or Paper 4 (Higher). It links to combustion and fuels in C6.2, testing for gases in C4.2 and separation methods in C2.1. Examiners regularly test the evidence for how the atmosphere changed, explanations of the greenhouse effect, interpreting climate data with its uncertainties, the sources and effects of pollutants such as carbon monoxide and sulfur dioxide, and the stages of water treatment.

What you need to know

• The early atmosphere The early atmosphere is thought to have been mainly carbon dioxide and water vapour from volcanoes. Water vapour condensed to form oceans, carbon dioxide dissolved in the oceans and formed sedimentary rocks, and photosynthesis by algae and plants added oxygen.
• The greenhouse effect Greenhouse gases such as carbon dioxide, methane and water vapour absorb long-wavelength infrared radiation emitted by the Earth and re-emit it, keeping the Earth warm. Human activities such as burning fossil fuels, deforestation and farming increase their concentrations.
• Climate change Increasing greenhouse gas levels are linked to rising global temperatures, causing sea level rise, more extreme weather and changes to habitats. Climate models are complex, so predictions have uncertainty, and data can be presented selectively in the media.
• Carbon footprint A carbon footprint is the total amount of greenhouse gases emitted over the full life cycle of a product, service or event. It can be reduced by using renewable energy, improving energy efficiency and carbon capture.
• Atmospheric pollutants Incomplete combustion produces toxic carbon monoxide and soot (particulates), which cause breathing problems and global dimming. Sulfur dioxide and oxides of nitrogen cause acid rain and respiratory problems.
• Potable water Potable water is safe to drink. Fresh water is treated by sedimentation, filtration and chlorination; in areas with little fresh water, seawater can be desalinated by distillation or reverse osmosis, which need a lot of energy.

Common mistakes in C6.3 Interpreting and Interacting with Earth Systems

• Confusing the greenhouse effect with ozone depletion. The greenhouse effect involves absorption of infrared radiation, not holes in the ozone layer.
• Saying greenhouse gases trap heat from the Sun directly. They absorb infrared radiation emitted by the Earth's surface.
• Writing that carbon monoxide causes acid rain. Sulfur dioxide and nitrogen oxides cause acid rain; carbon monoxide is toxic because it reduces the blood's ability to carry oxygen.
• Calling potable water pure water. Potable water is safe to drink but still contains dissolved substances.
• Stating that scientists are certain about exact future temperatures. Models have uncertainties, though the link between carbon dioxide and warming is well supported.

Try three C6.3 Interpreting and Interacting with Earth Systems exam-style questions