c9 - crude oils Flashcards
what are fossil fuels made of
formed from the remains of organic matter
types of fossil fuels
crude oil, natural gas, coal
fuel + oxygen
-> water + carbon dioxide
hydrocarbon
molecules made up of just hydrogen and carbon atoms
- they differ in size, which alters their properties
alkanes and their properties
- end in -ane
- general formula: CnH2n+2
- low reactivity
- complete combustion therefore useful as fuels
- saturated hydrocarbon
crude oil
a mixture of hydrocarbons
first ten alkanes
methane, ethane, propane, butane, pentane, hexane, heptane, octane, nonane, decane
saturated hydrocarbon
it does not have a double bond; an alkane
viscosity
being thicker and flowing easily
viscosity of hydrocarbons
- longer chain: higher viscosity
- lower chain: lower viscosity
boiling point of hydrocarbons
- longer chain: higher boiling point
- short chain: lower boiling point
flammability
- longer chain: less flammable
- short chain: more flammable
volatility
how easily it evaporates
volatility of hydrocarbons
long chain: high volatility
short chain: low volatility
uses of crude oil
- tarmac
- fuels
unsaturated hydrocarbon
has a double bond; an alkene
fractional distillation
the process of separating crude oil into groups of hydrocarbons with similar numbers of carbon atoms “fractions”
what are long chain and short chain hydrocarbons?
- long-chain: has lots of carbon atoms
- short-chain:few carbon atoms
explain the process of fractional distillation
EVAPORATION:
- evaporate the crude oil by heating it
- crude oil vapour is put into a fractionating column at the bottom and it rises upwards
CONDENSATION:
- temp is highest at the bottom and lowest and gets colder at the top
- LONG-CHAIN hydrocarbons condense at the bottom and are collected as liquids
- SHORT-CHAIN hydrocarbons have lower boiling points so they pass up the column at lower temps near the top
COLLECTION:
- the fractions are then collected and processed to create end products: fuel or feedstock
feedstock
materials used in an industrial process to make products
incomplete combustion
- if alkanes are burnt without enough oxygen, then carbon monoxide is released
2C + O2 => 2CO
properties of carbon monoxide
- colourless
- toxic
- odourless
complete combustion
- involves the release of energy (hence good fuels)
- the oxidation of carbon and hydrogen => dioxide and water
why do heavy fractions of crude oil not create good fuels?
- they have high boiling points
- don’t ignite easily
- have low volatility
cracking
the process that breaks down long-chain molecules into shorter-chain that are more useful
- an example of thermal decomposition
two types of cracking
catalytic cracking and steam cracking
what is catalytic cracking
- vapourised heavy hydrocarbons are passed over the top of a heated (zeolite) catalyst
- alkanes and alkenes are produced by the reaction eg. hexane => butane + ethene
what is steam cracking
- vapourised heavy hydrocarbons are combined with steam in a high temperature environment
- alkanes and alkenes are produced eg. decane => octane + ethene
uses of alkenes
- starting materials for chemicals like ethanol
- being combines to make polymers
