Chapter 22 - Maintaining Air Quality

When a substance undergoes combustion which requires oxygen to occur and ceases once the oxygen supply is cut

A fire blanket prevents oxygen in the air form getting to the flames and thus puts out the fire

78% Nitrogen 21% Oxygen 0.04% Carbon dioxide 0.96% Noble gases (mainly Argon) /Water vapour/other gases

Nitrogen is considered to be an inert gas as the N-N triple bond is relatively strong and hard to break

1) Combustion 2) Support patients with breathing difficulties (21% is insufficient to oxygenate their blood) 3) Oxidiser in welding that joins pieces of melts together strongly

Inert conditions for high temperature processes like in lightbulbs and in thermal purification of copper and steel

Fractional distillation - they all have different boiling points

N2: -196 Ar: -186 O2: -183

Harmful gases that should not be found in a sample of clean air

Air pollution is the introduction of unwanted and harmful chemicals into the atmosphere

Natural causes - e.g. lightning strikes, wildfires, volcanic eruptions Human activities - e.g. industrial emissions, combustion engine emissions and man made fires

1) Sulfur dioxide - colourless gas w pungent odour 2) Nitrogen oxides - NO is colourless and odourless & NO2 is red-brown with a pungent smell 3) Carbon monoxide - a colourless and odourless gas that is very toxic 4) Methane - a colourless and odourless gas that is highly flammable 5) Unburnt hydrocarbons - colourless gases that are naturally odourless but may be pungnet due to fuel additives 6) Ozone - a pale blue gas with a pungent odour

Source - combustion of fossil fuels & volcanic eruptions Harmful effects - breathing difficulties in humans and animals & SO2 + Nitrogen oxides react with oxygen to form acidic compounds to form acid rain (kills plants & aquatic life, corrodes buildings & structures made from limestone/marble/metal)

Source - vehicle combustion engines & lightning Harmful effects - breathing difficulties in humans and animals & SO2 + Nitrogen oxides react with oxygen to form acidic compounds to form acid rain (kills plants & aquatic life, corrodes buildings & structures made from limestone/marble/metal)

Source - incomplete combustion of carbon-based fuels Harmful effects - CO binds irreversibly with the haemoglobin in our red blood cells which lowers the ability of haemoglobin to transport oxygen to the rest of our body (loss of consciousness/death)

Source - anaerobic bacterial decay of organic substances & waste gases from cattle Harmful effects - methane is a major greenhouse gas that leads to global warming

Sources - vehicle combustion engines Harmful effects - eye and respiratory tract irritation & react with nitrogen oxides in the presence of sunlight to form photochemical smog (brown haze) - produces ozone, SO2 & NO2 (other pollutants)

Source - lightning, reactions between oxygen molecules & sunlight in upper atmosphere, reactions between unburnt hydrocarbons and nitrogen oxides in the presence of sunlight in the lower atmosphere Harmful effects - eye and respiratory tract irritation (breathing difficulties), causes chest pain/headache, slows down photosynthesis in plants (damage crops)

Between 5.0 and 5.5 due to naturally occurring oxides dissolving in the raindrops as they fall

pH of around 4.0. While this does not seem like a big difference, pH 4.0 is actually 10 to 30 times more acidic than pH 5.0 to 5.5

Acid rain leaches essentials nutrients like magnesium and calcium from the soil, which hampers the health and growth of trees. Acid rain can also lower the pH of soil below what many plant species can tolerate, killing them

Over time, the addition of acidic rainwater to a water body like a lake or a pond can cause the pH to drop out of the survivable range. Even species that can tolerate acidic conditions are not spared. The plants and animals they eat may not survive the low pH. Water bodies that have experienced prolonged exposure to acid rain are thus much less biodiverse

Modern vehicles with internal combustion engines come with catalytic converters that reduce the pollution they produce. In Singapore, vehicles undergo regular tests to ensure that their catalytic converters are functioning well and that their emissions are within an acceptable standard

• Located midway in the exhaust system of a vehicle, between the engine and the muffler • Contains a coating of catalysts made up of platinum, palladium and rhodium that speed up the conversion of harmful substances in the vehicle exhaust into less harmful substances • Catalysts are arranged in honeycomb structures that maximise the surface area for gases to interact with