IGCSE:Chemistry of the environment
Sub Topic:10.3 Air quality and climate
Syllabus Objectives:
CORE:
- 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
- State the source of each of these air pollutants, limited to:
- (a) carbon dioxide from the complete combustion of carbon-containing fuels
- (b) carbon monoxide and particulates from the incomplete combustion of carbon-containing fuels
- (c) methane from the decomposition of vegetation and waste gases from digestion in animals
- (d) oxides of nitrogen from car engines
- (e) sulfur dioxide from the combustion of fossil fuels which contain sulfur compounds
- State the adverse effect of these air pollutants, limited to:
- (a) carbon dioxide: higher levels of carbon dioxide leading to increased global warming, which leads to climate change
- (b) carbon monoxide: toxic gas
- (c) particulates: increased risk of respiratory problems and cancer
- (d) methane: higher levels of methane leading to increased global warming, which leads to climate change
- (e) oxides of nitrogen: acid rain, photochemical smog and respiratory problems
- (f) sulfur dioxide: acid rain
- State and explain strategies to reduce the effects of these environmental issues, limited to:
- (a) climate change: planting trees, reduction in livestock farming, decreasing use of fossil fuels, increasing use of hydrogen and renewable energy, e.g. wind, solar
- (b) acid rain: use of catalytic converters in vehicles, reducing emissions of sulfur dioxide by using low-sulfur fuels and flue gas desulfurisation with calcium oxide
- 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
- State the word equation for photosynthesis, carbon dioxide + water -> glucose + oxygen
EXTENDED:
- Describe how the greenhouse gases carbon dioxide and methane cause global warming, limited to:
- (a) the absorption, reflection and emission of thermal energy
- (b) reducing thermal energy loss to space
- Explain how oxides of nitrogen form in car engines and describe their removal by catalytic converters, e.g. 2CO + 2NO -> 2CO2 + N2
- State the symbol equation for photosynthesis, 6CO2 + 6H2O -> C6H12O6 + 6O2
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