sc20, fuels (paper 2) Flashcards
what is a crude oil
a fossil fuel formed over millions of years from ancient remains of marine organisms
define hydrocarbon
compounds of carbon and hydrogen atoms ONLY
what are the different possible bonds in a hydrocarbon molecule
- carbon __ carbon bonds
- carbon __ hydrogen bonds
what are the two things hydrocarbon molecules can consist of
- chains (with or without branches)
- rings of carbon atoms
what is a finite resource
- no longer being made or
- being made extremely slowly
why are sources from crude oil useful
- hydrocarbons are useful as fuels
- and as feedstock for the petrochemical industry
define feedstock
starting material for an industrial chemical process
define petrochemical industry
involves the use and manufacture of substances from crude oil
why can you use fractional distillation to seperate crude oil into simpler, more useful mixtures
the different hydrocarbons have different boiling points
what is a fraction in terms of crude oil
a mixture of hydrocarbons with similar boiling points and number of carbon atoms
what happens to the gas fraction in fractional distilaltion for crude oil
doesn’t condense and leaves at the top
what happens to the bitumen fraction in fractional distilaltion for crude oil
doesn’t evaporate and leaves at the bottom
what happens to the ‘other’ fraction in fractional distilaltion for crude oil
they are liquid at room temp and are useful as fuels
true or false: most hydrocarbons are alkanes
true
true or false: most hydrocarbons are alkenes
false
what happens as the number of carbon and hydrogen atoms in a hydrocarbon molecule increase
- the strength of the intermolecular forces increases
- more energy must be transfered to overcome these forces
- the boiling point increases
what is an alkane
form a homologous series of hydrocarbons
what is a homologous series
a series of compounds:
- in which molecular formulae of neighbouring members differ by CH2
- that show a gradual variation in physical properties
- that have similar chemical properties
what happens when alkanes undergo complete combustion
they form carbon dioxide and water vapour
what do alkanes end in
ane
why does incomplete combustion happen
when the supply of oxygen to a burning fuel is limited
what happens in complete combustion
- hydrogen is oxidised to water vapout
- carbon is oxidised to carbon dioxide
- energy is transferred to surroundings by radiation as heat and light
what happens in incomplete combustion
- carbon may be partially oxidised to carbon dioxide, CO
- carbon may be released at carbon particles or soot
- less energy is given out
in combustion, what depends on how much carbon is produced
how much oxygen is available for oxidation
why is carbon monoxide bad
- attaches to haemoglobin in red blood cells
- preventing oxygen from attaching
- reducing th eoxygen carries around the body by bloodstream
what two things makes carbon monoxide hard to detect
- colourless
- odourless
how can we detect gas
electronic carbon monoxide detectors
why is soot bad
- builds up in chimneys where it may eventually cause fires and blacken buildings
- tiny soot particles may cause lung diseases such as bronchitis
- or make existing lung diseases worse
what is acid rain
rain more acidic than usual
how is acidic rain made
when sulfur dioxide or oxides of nitrogen dissolves in water in the air
how is sulfur dioxide created in the atmosphere
- hydrocarbon fuels contain impurities of sulfur compounds
- when the fuel burns, the sulfur in these impurities are oxidsed
- to form sulfur dioxide
how are oxides of nitrogen created in the atmosphere
- air goes inside to engine so the fuel can burn
- nitrogen and oxygen from the air react together at high tempuratures
- in the engine to produce oxides of nitrogen
what can acid rain do to our environment
- speeds up the weathering of buildings and statues
- damages trees
- acidifies rivers, lakes, sails - which harms organisms livin gin them
how can we reduce problems caused by acid rain
- remover sulfur from fueks before selling
- ‘flue gas desulfurisation’ - preventing sulfur dioxide leaving power station chimneys
- adding calcium carbonate/hydroxide to fiels and lakes to neutralise excess acid from acid rain
what else, other than petrol or diesel oils, can be used for cars
hydrogen
list the fossil fuels obtained from crude oil
- petrol
- deisel oil
- fuel oil
what is petrol used in
cars
what is diesel oil used in
cars and trains
what is fuel oil used in
large ships and power stations
true or false: fossil fuels are non renewable
true
true or false: fossil fuels are renewable
false
what is a non renewable resource
resources used up faster than they are formes
give the symbol equation for the combustion of hydrogen
2 H2 + O2 –> 2 H2O
how can hydrogen be manufactures
- electrolysis of water
- cracking of oil fractions
- reaction of natural gas with steam
give the symbol equation for the reaction of natural gas with steam
CH4 (g) + 2 H2O (g) –> CO2 (g) + 4 H2 (g)
what are the qualities of a good fuel
- burn easily (easy to ignite and stay alight)
- not produce soot, smoke, or ash
- release a lot of energy when it burns
- easy to store and transport safely
pros of petrol
- burns easily
- doesn’t produce ash
- a liquid (easy to store and transport)
- releases more enrgy per kg than coal or wood
cons of petrol
- produces carbon dioxide, monoxide and water
pros of hydrogen as a fuel
- burns easily
- doesn’t produce ash or smoke
- only produces water
- releases 3x more energy than petrol
cons of hydrogen as a fuel
- gas (hard to store, at high temps)
- filling stations have to be adapted
what is cracking
a process carried out on fractions in oil refineries after fractional distillation
what is a summarized version of cracking
breaking down larger alkanes into smaller, more useful alkanes (for fuels) and alkenes (for polymers)
true or false: paraffin is an alkene
false
true or false: paraffin is an alkane
true
descrube how paraffin can be cracked
- the polous pot catalyst is heated strongly
- liquid paraffin is heated and evaporates
- paraffin vapour passes over the hot porous pot and the hydrocarbon molecules break down
- one of the products is thene (gas) and collects in the other tube
