C9: Crude oil and fuels Flashcards
what is crude oil
finite resource found in rocks.
it is formed over millions of years from tiny sea animals and plants
mixture of carbon compounds
what is a hydrocarbon
a compound made of only hydrogen and carbon
what are the different separate parts of crude oil called
fractions
how do we separate crude oil
fractional distillation
what are alkanes
saturated hydrocarbons with single covalent bonds
what’s the general formula for alkanes
C(n)H(2n+2)
properties of a short chain of hydrocarbons
-lower boiling point
-higher volatility (tendency to turn into gas)
-low viscosity (runny)
-higher flammability
properties of long chain of hydrocarbons
-higher boiling point
-lower volatility (tendency to turn into gas)
-high viscosity (thick)
-lower flammability
why do different fractions of crude oil have different boiling points
they have differently sized molecules.
what kind of boiling points are at the top of the crude oil fractionating column?
lower ones (cooler temps)
order of boiling points in crude oil, lowest to highest
refinery/petroleum gas
gasoline/petrol
kerosene
diesel
whats at the bottom of a fractionating column?
residue, thick mixture of hydrocarbons used of roads and roofs.
what are the lighter fractions of crude oil useful for?
fuels, e.g. propane
the products of the complete combustion of a hydrocarbon are
carbon dioxide and water
when does incomplete combustion happen
when there is not enough oxygen
what is the process where hydrocarbon molecules can be broken down into smaller ones
cracking
why do we use cracking
the smaller hydrocarbons are more useful
how is cracking done
a fraction from crude is vaporised and then either:
-passed over a hot catalyst
-mixed with steam and heated to a high temperature
what kind of reaction is cracking
thermal decomposition
do alkenes burn in air
yes, but not as well as equally small alkanes
what is the positive test for an alkene
it turns orange bromine water colourless
