crude oil/ cracking Flashcards
crude oil
is a mixture of hydrocarbons
fossil fuel
formed of dead remains of plants and animals
non renewable
eg coal, natural gas, oil
hydrocarbon
a compound that only contains hydrogen and carbon
( simple covalent molecules)
refining crude oil
big mixture of different compounds isn’t useful so is refined
separated by fractional distillation
fraction
mixture of hydrocarbon molecules with a similar no. carbons (similar chain lengths) and similar bp.
oil fractions order
refinery gases
gasoline
kerosene
diesel
fuel oil
bitumen
process of fractional distillation
- crude oil is heated and enters fractionating column as a vapour
- column is cooler at top and warmer at bottom
- vapours rise up column once hydrocarbon cools to a temp below bp it condenses
- hydrocarbons with lower bp are nearer top creating fractions
use of refinery gases
bottles gas
use of gasoline
car fuel
use of kerosene
aircraft fuel
use of diesel
fuel in diesel engines
use of fuel oil
fuel for ships power stations
bitumen
for roads and roofs
viscosity
how easily something flows
volatility
how easily something vaporises
flammability
how easily something burns/ ignites
boiling point trend
increases as you go down
viscosity trend
increases as you go down (from runny to thick)
volatility trend
decreases as you go down
flammability trend
decreases as you go down
colour trend
darker as you go down
size trend
get bigger as you go down
why must sulphur impurities be removed
when you burn an impure fuel SO2 will be made which causes acid rain and pollution
what is cracking
the thermal decomposition of large hydrocarbons (alkanes) into smaller (alkanes + alkenes) that are more useful
why is cracking important
long chain are in lower demand/use - large surplus
short chain are in larger demand/ use but low supply
so long are cracked into smaller more useful to meet demand
cracking in the lab
wool soaked in paraffin (gentle heat) and a catalyst (strong heat) is heated in a boiling tube
gas is made and collected over water
suck back
remove delivery tube before stopping hearing to prevent this
catalyst in cracking
silica or alumina
temperature of cracking
600-700°C
purpose of wool
to absorb liquid and keep it at end of tube
why is mineral wool gently heated
to vapourier it but prevent it combusting
why are pottery fragments strongly heated
as gas molecules hit hot catalyst they break up into smaller molecules
strong heat prevents suckback
