Crude oil and fuels Flashcards
What is crude oil and how was it formed?
Crude oil is a finite resource made of a mixture of hydrocarbons.
It formed when decomposed ancient biomasses died, were buried and pressured in the earth’s crust and reemerged in reservoirs as natural gas and oil.
What conditions are needed to make crude oil?
-high temperatures
-high pressure
-absence of oxygen
What is crude oil made out of?
A mixture of hydrocarbons
What are hydrocarbons?
COMPOUNDS that ONLY contain hydrogen and oxygen ions.
What are alkanes?
A branch of hydrocarbons where carbons are single bonded 4 times, and hydrogens once. They are fully saturated meaning that they contain the maximum amount of hydrogen atoms in the molecule as possible.
Give examples of alkanes:
-methane
-ethane
-propane
-butane
What is the general chemical formula of alkanes (in terms of n)
C(n) H(2n+2)
What are alkenes?
A branch of hydrocarbons which contain at least one double bond between two carbons. They are unsaturated.
What is the general chemical formula of alkenes (in terms of n)
C(n) H(2n)
Why would we want to extract alkenes from crude oil?
-They can be used to make plastics.
What separation method can we use to separate the different hydrocarbons in crude oil?
Fractional distillation
What five components is crude oil made out of?
-bitumen (used in road construction)
-diesel (fuel for cars, vans and lorries)
-petrol (fuel for cars)
-kerosene (fuel for aircrafts)
-naptha (to make chemicals for manufacturing)
Explain how fractional distillation works:
- crude oil is heated up to around 350°
- it flows into a distilling cylinder which decreases in temperature the higher you go.
- components with lower boiling points would turn into gasses and rise.
- temperature specific sifts with holes help gas pass through and condenses the gas at their boiling points back into liquids.
- the liquid gets collected into containers.
What is fractional distillation?
a method of extracting the different components in crude oil, by using its different physical properties (boiling points) to evaporate and condense its hydrocarbons into separate categories using a fractionating column.
In a fractionating column, describe the particle’s characteristics at the top and bottom:
at the top, the molecules are smaller chain hydrocarbons that have lower boiling points and are highly flammable, they are also less viscous.
at the bottom, the hydrocarbons have longer chains and have higher boiling points, they are more viscous.
What is a fraction?
a mixture of hydrocarbons that have similar boiling points
Starting from the top, list the order of the 6 fractions in a fractionating column:
-refinery gas
-petrol
-naptha
-kerosene
-diesel
-bitumen
Explain the pattern between the length of hydrocarbon chains and their boiling points:
as the length of the hydrocarbon chain increases, the intermolecular force between the hydrocarbons molecules grow stronger because they need to hold bigger molecules together, this means that their boiling points increase as they require more energy to break these forces apart.
What is cracking?
used to break down larger chained alkane hydrocarbons into smaller chains that produces a smaller alkane and alkene, which can be sold for fuel or to manufacture plastics.
What are the 2 methods of cracking?
- Heat up the alkane at a high temperature with steam. (thermal cracking)
- evaporate the alkane to pass over a chemical catalyst. (catalytic cracking)
Explain the bromine test, including its purpose and results:
the bromine test includes dribbling water into a sample. since an alkane is fully saturated, the bromine in the bromine water will not bond with the hydrocarbon resulting in the orange hint being visible, whereas an alkene (who’s unsaturated) will break its carbon double bond and bond to 2 bromide atoms, causing the sample to turn colourless.
What does ‘saturated’ mean?
that it doesn’t contain double bonds
What is hydrogenation?
using hydrogen and temperatures to break alkene double bonds, creating an alkane
Describe how hydrogenation is involved in making margarine:
margarine is made of unsaturated fats, like olive oil, which make the fats liquid. when we hydrogenase the oil, and make the hydrocarbons alkanes, the structure becomes more rigid, making it more solid as it increases its melting point.
Describe the differences between combustion and incomplete combustion:
complete combustion is when there is enough oxygen around to react with the fuel, this produces CO₂ and H₂O. the flame given off is blue because it is releasing the maximum amount of thermal energy.
incomplete combustion is when there is a lack of oxygen to react with the fuel, this produces carbon monoxide, carbon (soot) and water. the flame given off it red/yellow, because it is releasing less oxygen due to its incomplete combustion.
What are the similarities in the out come of complete and incomplete combustion?
-both produce CO₂ and H₂O
-carbon and oxygen will be oxidised in the reactions
What is combustion?
the rapid chemical reaction when a substance reacts with oxygen involving the production of energy and light
Evaluate thermal and catalytic cracking:
Thermal:
- thermal requires high temperatures and pressures so is very energy intensive and costly, making it uneconomical to use.
Catalytic:
- catalytic requires a lower temperature and a quite normal pressure whilst using a catalyst that can be reused again. this main it more cost effective and more economical. the catalyst also reduces the extraction time, so a higher yield can collected to match demand.
Which type of cracking is more economical and why? (3)
Catalytic cracking is done at lower temperatures at a relatively normal pressure, this requires less thermal energy which reduces the cost of electricity to raise the hydrocarbon’s temperature, the catalyst can also be reused, and speeds up the extraction process so companies can produce higher yields of the alkanes/alkenes they want, increasing their income.
