Chemistry IGCSE - Chemistry of the environment

Test with using cobalt(II) chloride for presence of water

Blue → pink (+)

Test with copper(II) sulfate for presence of water

White → blue (+)

Test for purity of water using melting point and boiling point

Pure water → boiling point of 100°C → begins to boil either below or above 100°C → liquid contains impurities

Distilled water is used in practical chemistry → contains fewer chemical impurities rather than tap water

Describe treatment of domestic water supply in terms of sedimentation and filtration to remove solids

Sedimentation → allows solid particles in water to settle to bottom of tank → easier to remove them → filtration further cleanses water by passing it through layers of sand, gravel, or other materials to trap → remove remaining solid particles

Describe treatment of domestic water supply in terms of use of carbon to remove tastes and odours

Carbon filters → used to absorb and remove organic compounds that can cause undesirable tastes + odours in water → helps in reducing chemical pollutants

Describe treatment of domestic water supply in terms of chlorination to kill microbes (pathogens)

Chlorination → adding chlorine/chlorine compounds to water as a disinfectant → method to kill bacteria, viruses, and other pathogens → water safe for human consumption

Composition of clean, dry air

78% nitrogen (N₂) + 21% oxygen (O₂)

rest → mixture of noble gases + carbon dioxide (CO₂)

Source of this air pollutants: carbon dioxide

Carbon dioxide → complete combustion of carbon-containing fuels

Source of this air pollutants: carbon monoxide and particulates

Carbon monoxide and particulates → incomplete combustion of carbon containing fuels

Source of this air pollutants: methane

Methane → decomposition of vegetation and waste gases from digestion in animals

Source of this air pollutants: oxides of nitrogen

Oxides of nitrogen → car engines

Source of this air pollutants: sulfur dioxide

Sulfur dioxide → combustion of fossil fuels which contain sulfur compounds

Adverse effect of these air pollutants: carbon dioxide

Carbon dioxide → higher levels of carbon dioxide → increased global warming → climate change

Adverse effect of these air pollutants: carbon monoxide

Carbon monoxide → toxic gas

Adverse effect of these air pollutants: particulates

Particulates → increased risk of respiratory problems + cancer

Adverse effect of these air pollutants: methane

Methane → higher levels of methane → increased global warming → climate change

Adverse effect of these air pollutants: oxides of nitrogen

Oxides of nitrogen → acid rain + respiratory problems

Adverse effect of these air pollutants: sulfur dioxide

Sulfur dioxide → acid rain

Explain strategies to reduce effects of climate change: planting trees

Trees absorb carbon dioxide during photosynthesis → removing it from atmosphere → reduce greenhouse effect → improves air quality + provides ecological benefits

Explain strategies to reduce the effects of climate change: reduction in livestock farming

Livestock farming produces methane → reducing livestock farming → decrease methane emissions → encourage more sustainable agricultural practices

Explain strategies to reduce the effects of climate change: decreasing use of fossil fuels

Fossil fuels release carbon dioxide when burned → reducing their use + transitioning to cleaner energy sources → can cut emissions + reduce air pollution

Explain strategies to reduce the effects of climate change: increasing use of hydrogen and renewable energy, e.g. wind, solar

Hydrogen energy produces water as a byproduct → cleaner alternative to fossil fuels → renewable energy sources → e.g. wind + solar power generate electricity without emitting greenhouse gases → help replace fossil fuel-based power generation → reduce global warming

Explain strategies to reduce the effects of acid rain: reducing emissions of sulfur dioxide by using low-sulfur fuels

Switching to fuels with lower sulfur content → reduces sulfur dioxide emissions during combustion → decreasing primary contributor to acid rain

Explain strategies to reduce the effects of acid rain: flue gas desulfurization with calcium oxide

Treats flue gases with calcium oxide to chemically remove sulfur dioxide → converts it into calcium sulfate → non-harmful + can be utilized in industrial products → cuts emission of sulfur dioxide into atmosphere

Describe how the greenhouse gases carbon dioxide and methane cause global warming: absorption, reflection and emission of thermal energy

Both gases absorb infrared radiation (thermal energy) from Earth → re-emits it in all directions → including back toward the surface → trapping heat in atmosphere

Describe how the greenhouse gases carbon dioxide and methane cause global warming: reducing thermal energy loss to space

By absorbing and re-emitting infrared radiation → CO2 + CH4 decrease amount of heat that escapes into space → enhancing greenhouse effect → warming the planet

Explain how oxides of nitrogen form in car engines

Oxides of nitrogen (NO_x) form in car engines → due to high-temperature combustion → at these temperatures → nitrogen (N₂) + oxygen (O₂) from air react to form NO and NO₂

Describe their removal by catalytic converters:

2CO + 2NO → 2CO₂ + N₂

Catalytic converters reduce NOx emissions by fusing the reaction: 2CO + 2NO → 2CO₂ + N2₂ → carbon monoxide (CO) reacts with nitric oxide (NO) → produces nitrogen gas (N₂) and carbon dioxide (CO₂) → converts harmful emissions into less harmful gases before they are released into atmosphere