C9 - Crude Oils & Fuels Flashcards
What is a hydrocarbon?
molecules only containing H & C
What is crude oil?
mixture of diff. hydrocarbons @ diff. lengths
Define alkane.
saturated hydrocarbons (single cov. bond btwn carbons) ending in -ane
What is the general formula of an alkane?
Cn H2n+2
What are the prefixes for the first 4 hydrocarbons?
me-
eth-
prop-
but-
Define viscosity.
how thick a liquid is
How does chain length affect the viscosity of hydrocarbons?
long chain length = high viscosity (thick/gloopy)
short chain length = low viscosity (runny/thin)
Define flammability.
how easily something can catch on fire
How does chain length affect the flammability of hydrocarbons?
long chain length = less flammable
short chain length = v flammable
Define boiling point.
temp which liquid -> gas
How does chain length affect the boiling point of hydrocarbons?
long chain length = high BP
short chain length = low BP
What holds hydrocarbons together?
weak intermolecular forces
How many bonds can a carbon atom form?
4 covalent bonds
How do hydrocarbon fuels release energy?
by combustion
What is complete combustion?
carbon & hydrogen atoms react with O2 in combustion & bcm oxidised
if oxygen is unlimited, reaction -> CO2 + H2O
How can be break down long chain hydrocarbons, into smaller more useful hydrocarbons?
cracking
What are short chain hydrocarbons mostly used for?
fuels
Other than short chain hydrocarbons, what else is produced in cracking?
alkenes
What is needed in catalytic cracking?
high temp. & catalyst
What is needed in thermal cracking?
high temp. & steam
What is the functional group of alkenes?
C=C (double bond, 2 carbons atms)
Which is more reactive, alkenes or alkanes?
alkenes
What is the test for alkenes? What signifies a positive result?
add bromine water
+ = orange -> colourless
How are crude oils formed?
Crude oil is a finite resource that is found in the Earth’s crust. It is the remains of organisms that lived and died millions of years ago - mainly plankton which was buried in mud
what is the process of fractional distillation?
crude oil is heated until most hydrocarbons are gases
gases enter colum, which has a temp gradient
vapours move up columns & condense at their boiling points
longer hydrocarbons have higher boiling points & shorter hydrocarbons have lower boiling points
so hydrocarbons are seperated on length
