GCSE Chemistry : C1: Air Quality

. Rasbash
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OCR 21st Century - C1 Flashcards

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EVOLUTION OF THE ATMOSPHERE Phase 1 : The First 2 Billion Years The Earth's surface was originally molten, with no atmosphere. Eventually, it cooled forming a thin crust. Volcanoes continued to erupt, emitting significant amounts of gas e.g. Carbon Dioxide, Water Vapour and Nitrogen- this formed our atmosphere. No oxygen. Water Vapour condensed and formed oceans.
EVOLUTION OF THE ATMOSPHERE Phase 2 : The Next 2 Billion Years Plants evolved in the CO2 heavy atmosphere. A lot of the early CO2 dissolved into the oceans. Photosynthesis also removed it and produced oxygen. Dead plants got buried under layers of sediment, the carbon they'd removed from the atmosphere became trapped as insoluble carbonates and fossil fuels
EVOLUTION OF THE ATMOSPHERE Phase 3 The increase of oxygen in the atmosphere killed off many early organisms that couldn't tolerate it, this allowed more complex organisms to evolve. Now there is barely any carbon dioxide left.
THE ATMOSPHERE TODAY What does our atmosphere mainly consist of? Nitrogen ... 78% Oxygen ... 21% Argon ... 1% These are slightly rounded figures, the atmosphere also contains small amounts of carbon dioxide and various other gases
THE ATMOSPHERE TODAY Human activity and Pollutants The main components of our atmosphere are fairly constant however human activity is adding pollutants through acts such as combustion (power stations, vehicles..). They can be directly harmful -e.g. carbon monoxide- or indirectly harmful -e.g. sulphur dioxide in acid rain.
FOSSIL FUELS How are they formed? Hydrocarbons. Formed over millions of years from the remains of dead plants and animals. They are then drilled out of the ground and refined to make useful products e.g. Petrol. Coal is different as it's not a hydrocarbon but just carbon with lots of impurities
FOSSIL FUELS Combustion Combustion is an oxidation reaction. When a hydrocarbon burns, the hydrogen atoms combine with oxygen to form water. The carbon atoms also combine with oxygen, this creates carbon dioxide.
AIR POLLUTION - CARBON Carbon Dioxide (CO2) 1 carbon atom, 2 oxygen. Stays in the atmosphere until it's removed naturally through photosynthesis or dissolved in water. Human activity (e.g. burning fuels) has increased levels of CO2 in the atmosphere, this leads to global warming and the greenhouse effect.
AIR POLLUTION - CARBON Carbon Monoxide (CO) 1 carbon atom, 1 oxygen. Produced by incomplete combustion (lack of oxygen). It is poisonous as it limits the amount of oxygen our blood can transport around the body.
AIR POLLUTION - CARBON Particulate Carbon Incomplete combustion often produces tiny particles of carbon. If they escape into the atmosphere they just float around until they eventually deposit themselves as soot. This is what makes buildings look dirty.
AIR POLLUTION - SULPHUR Where does it come from? Many of our fuels contain impurities as they're extracted straight from the Earth's crust. Sulphur is one of these impurities. While the fuel is burning, sulphur does also, producing the pollutant sulphur dioxide. This usually ends up in our atmosphere when power stations and vehicles burn fossil fuels.
AIR POLLUTION - SULPHUR Acid Rain Sulphur Dioxide: 1 sulphur atom, 2 oxygen. Usually, it leaves the atmosphere in the form of acid rain, it reacts with the moisture in clouds forming dilute sulphuric acid. This causes lakes to become acidic, killing plants and animals. It also kills trees and damages building/ statues made of certain stones e.g. limestone.
AIR POLLUTION - NITROGEN How is it formed? Fossil fuels burn at such high temperatures that nearby atoms react with each other. Nitrogen reacts with Oxygen to produce small amounts of the nitrogen oxide compounds: nitrogen monoxide and dioxide. This occurs in our car engines and these pollutants normally go directly to the atmosphere.
AIR POLLUTION - NITROGEN Nitrogen Monoxide (NO) / Nitrogen Dioxide (NO2) Nitrogen Monoxide: 1 nitrogen atom, 1 oxygen. Formed when nitrogen & oxygen in the air are exposed to high temperatures. Nitrogen Dioxide: 1 Nitrogen atom, 2 oxygen. Formed when NO reacts with oxygen in the air. Reacts with moisture in the clouds to form dilute nitric acid- also falls as acid rain
REDUCING POLLUTION - POWER STATIONS Reducing Electricity The easiest way to reduce pollution is by limiting electricity usage so fewer fossil fuels would be needed and, in turn, less pollution created. However, we've all adjusted to the high consumer lifestyle so it would be hard to make a change on large enough scale. Reduces carbon dioxide emissions.
REDUCING POLLUTION - POWER STATIONS Alternative Methods Sulphur can be removed from natural gas/fuel producing less sulphur dioxide. Also, particulates can be removed when coal is burned. The acidic Sulphur Dioxide can be removed with an alkali (wet scrubbing). You can use seawater which dissolves the sulphate or an alkaline slurry which produces a solid waste product.
REDUCING POLLUTION - CARS Catalytic Converters These convert harmful nitrogen oxide to nitrogen and oxygen through reduction and convert harmful carbon monoxide to carbon dioxide through oxidation. MOT tests check that cars are within the legal limit of polluting emissions. However, public transport would decrease pollution even more.
REDUCING POLLUTION - CARS Alternative Methods of Powering Cars Car engines can be run by burning biofuels, a renewable (and carbon neutral) energy source made from plants and waste which only produces CO2 and H2O when burned. Electric batteries can also power cars, produces no exhaust fumes but electricity is also formed by burning fossil fuels so doesn't remove pollution just moves it.
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