Notesale: Turn your study into money

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Fuels
crude oil:
complex mixture of hydrocarbons: compounds containing carbon / hydrogen only
containing molecules in which carbon atoms are in chains or rings
important source of useful substances – fuels / feedstock for petrochemical industry
Non-renewable
Fractional distillation: separation of crude oil into more simple/useful mixtures
Viscous crude oil pumped in
Heated & vaporised
Bitumen leaves as liquid: too high boiling-point / longest carbon chain / most viscous
Fractions condense just below their boiling point and are carried out at different levels –
separated
uses
Gases: domestic heating/cooking
Petrol: Fuel for cars
Kerosene: fuel for aircraft
Diesel oil: fuel for cars/trains
Fuel oil: fuel for large ships & power stations
Bitumen: surfacing roads/roofs
Differences between hydrocarbon’s fractions – determined by intermolecular forces holding
chain together
Viscosity: longer is thicker – stronger force between hydrocarbon molecules – harder for
liquid to flow
Flammability: shorter is easier to ignite
Boiling-point: shorter is lower – intermolecular forces of attraction in long molecules are
harder to break
Length of chain / amount of carbon atoms: increase – more atoms moving together – heavier
homologous series: series of compounds
same general formula: CnH2n+2
Consecutive compounds differ by CH2 in molecular formulae
Physical properties: gradual variation
chemical properties: similar
complete combustion of hydrocarbon: produces carbon dioxide & water
Energy given out – exothermic
incomplete combustion of hydrocarbons: produces carbon & carbon monoxide
When hydrogen burned in limited supply of oxygen
Product has less oxygen than carbon dioxide: carbon monoxide
Carbon – soot form

carbon monoxide: toxic gas
problems caused by incomplete combustion producing carbon monoxide & soot
In appliances that use carbon compounds as fuels:
Carbon monoxide: Can bind to red blood cells – stop blood carrying oxygen around body
properly
Carbon/soot: Tiny particles of carbon can be released into atmosphere and turn to soot when
they fall back to ground Makes buildings dirty / reduces air quality / respiratory problems
sulfur dioxide: produced from sulfur impurities in some hydrocarbon fuels
Acid rain: when sulphur dioxide dissolves in clouds/rain water
harmful to our health
dissolves limestone
trees/animals die
engines: oxygen/nitrogen can react together at high temperatures to produce nitrogen
oxides – pollutants
Internal combustion of car engines: cause reaction between nitrogen/oxygen to produce
nitrogen oxides
Harmful pollutants – contribute to acid rain
Photochemical smog: type of air pollution that causes breathing difficulties
Hydrogen as fuel in cars – rather than petrol
Advantages
Clean fuel / Only waste is water / Obtained from water – renewable source
Limited supply of crude oil / Petrol produces CO2 – causes global warming
Disadvantages
Expensive to manufacture
Manufacture uses fossil fuel energy
Hard to store – flammable & leaks easily
Not widely available
Petrol / kerosene / diesel oil: non-renewable fossil fuels obtained from crude oil
Methane: non-renewable fossil fuel found in natural gas
Cracking: Long-chain hydrocarbon to shorter alkane + alkene
Breaks down long/saturated hydrocarbon molecules (alkanes) into more useful alkanes or
smaller/unsaturated alkenes
Form of thermal decomposition: when substance breaks down into at least 2 new ones when
you heat it
Vaporised hydrocarbons passed over catalyst (alumina / silica / aluminium oxide) at very high
temperature
cracking necessary to supply for the demand

Earth and atmospheric science
Started molten
gases produced by volcanic activity: CO2 / water vapour / traces of methane / ammonia
Earth’s early atmosphere + its evidence
Little/no oxygen: increased due to growth of primitive plants to photosynthesise
Large amount of carbon dioxide – decreased for photosynthesis & dissolved into oceans
(fossil fuels/sedimentary rock)
water vapour – condensed to form oceans as Earth cooled down
small amounts of other gases
Nitrogen increase: soil/bacteria/ammonia reacted with oxygen
Ammonia decrease: reacted with oxygen – produced nitrogen, less volcano eruptions
chemical test for oxygen: Check if gas will relight glowing splint
Greenhouse effect
Carbon dioxide / methane / water vapour
Act as insulating layer
Absorb lots of long-wavelength infrared radiation from Earth’s surface
They re-emit this radiation in all directions – some re-emitted back towards earth
evidence for human activity causing climate change
correlation between: change in atmospheric carbon dioxide concentration / consumption
of fossil fuels / temperature change
Recently: average temperature at Earth’s surface increases as level of CO2 increases
Increased energy consumption: mainly from burning fossil fuels – releasing CO2
Uncertainties caused by: location where these measurements are taken / historical
accuracy
Historical data: less accurate – less data taken in fewer locations & less accurate methods
Estimates: tree rings / fossils / gas bubbles trapped in ice sheets – less representative of
global levels
composition of today’s atmosphere
Nitrogen: 78%
Oxygen: 21%
Argon: 0
...
04%
Other: 0

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