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10. Chemistry of the environment

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  1. 10.1 Water

    1. 10.1.1Chemical tests for the presence of

      • Describe chemical tests for the presence of water using anhydrous cobalt(II) chloride and anhydrous copper(II) sulfate

    2. 10.1.2To test for the purity of water using

      • Describe how to test for the purity of water using melting point and boiling point

    3. 10.1.3Distilled water is used in practical

      • Explain that distilled water is used in practical chemistry rather than tap water because it contains fewer chemical impurities

    4. 10.1.4Substances found in natural water

      • State substances found in natural water: dissolved oxygen, metal compounds, plastics, sewage, harmful microbes, fertiliser nitrates, and phosphates from fertilisers/detergents

    5. 10.1.5Some of these substances are

      • State: some of these substances are beneficial, (a) dissolved oxygen for aquatic life (b) some metal compounds provide essential minerals for life

    6. 10.1.6Harmful substances: toxic metal

      • State harmful substances: toxic metal compounds, plastics harming aquatic life, sewage microbes causing disease, and nitrates/phosphates causing deoxygenation and aquatic damage. Eutrophication details not required

    7. 10.1.7Treatment of the domestic water supply

      • Describe treatment of the domestic water supply in terms of: (a) sedimentation and filtration to remove solids (b) use of carbon to remove tastes and odours (c) chlorination to kill microbes

  2. 10.2 Fertilisers

    1. • State: ammonium salts and nitrates are used as fertilisers

    2. • Describe use of NPK fertilisers to provide the elements nitrogen, phosphorus and potassium for improved plant growth

  3. 10.3 Air quality and climate

    1. • State the composition of clean, dry air as approximately 78% nitrogen, N2, 21% oxygen, O2 and the remainder as a mixture of noble gases and carbon dioxide, CO2

    2. • State air pollutant sources: CO2 from complete combustion; CO/particulates from incomplete combustion; methane from decomposing vegetation and animal digestion; nitrogen oxides from car engines; sulfur dioxide from sulfur-containing fossil fuels

    3. • State pollutant effects: CO2 and methane increase global warming/climate change; CO is toxic; particulates increase respiratory/cancer risk; nitrogen oxides cause acid rain, photochemical smog and respiratory problems; sulfur dioxide causes acid rain

    4. • Describe how the greenhouse gases carbon dioxide and methane cause global warming, (a) the absorption, reflection and emission of thermal energy (b) reducing thermal energy loss to space

    5. • Explain reduction strategies: for climate change, plant trees, reduce livestock, use less fossil fuel, increase hydrogen/renewables; for acid rain, use catalytic converters, low-sulfur fuels and flue gas desulfurisation with calcium oxide

    6. • Describe photosynthesis as the reaction between carbon dioxide and water to produce glucose and oxygen in the presence of chlorophyll and using energy from light

    7. • State the word equation for photosynthesis, carbon dioxide + water → glucose + oxygen

    8. • Explain how oxides of nitrogen form in car engines and describe their removal by catalytic converters, e.g. 2CO + 2NO → 2CO2 + N2

    9. • State the symbol equation for photosynthesis, 6CO2 + 6H2O → C6H12O6 + 6O2