Paper 2 - Organic Flashcards
Crude Oil?
refined crude oil in rocks. Crude oil is a finite resource (if we continue using it, then crude oil will one day run out)
how was crude oil formed?
From the remains of tiny sea creatures called plankton, which were buried in mud, over millions of years ago
hydrocarbon?
Are molecules made up with hydrogen and carbon atoms only e.g. Methane CH4
H H—C—H H
What is crude oil a mixture of?
Molecules called hydrocarbons e.g. Methane CH4
what is an alkane?
scientist say they are saturated molecules.
They have a general formul CnH2n+2
This is because if we know the number of carbon atoms in the alkane (n) then we can calculate the number of hydrogen atoms
Ethane?
C2H6
H H H—C—C—H H H
Propane?
C3H8
H H H H—C—C—C—H H H H
Butane?
C4H10
H H H H H—C—C—C—C—H H H H H
what is viscosity?
Tells us the thickness of a fluid
What happens as the size of the hydrocarbon molecules increase e.g. Methane ➡️ Ethane ➡️ Propane etc?
the molecules get more viscous (thicker and move more slowly)
Flammability?
Tells us how easily a hydrocarbon combusts (burns)
Are short chain hydrocarbons flammable?
Yes extremely flammable
That’s why we use Methane in bunsen burners
The longer the chain of hydrocarbons…?
The more difficult they are to burn
Do short chain hydrocarbons have a low or high boiling point?
Low boiling point e.g. All the 4 hydrocarbons are gas at room temperature
When do hydrocarbon fuels release energy?
when combusted (burned)
What happens during combustion of fuel?
the carbon and hydrogen atoms in the fuel react with oxygen. They are oxidised
Complete combustion?
During combustion, if the oxygen is unlimited, the reaction produces water and carbon dioxide
In fractional distillation what is crude oil separated into?
fractions. Fractions contain hydrocarbons with a similar number of boiling points
Fractional distillation to seperate crude oil?
Firstly the crude oil is heated to a very high temperature which causes it to boil (all of the hydrocarbons evaporate and turn into a gas). The crude oil vapour is now fed into the fractional distillation column. It it hotter at the bottom but cooler at the top. The hydrocarbon vapours now rise up the column. When the hydrocarbons condense, the liquid fractions are then removed. The remaining hydrocarbons continue moving up the column. They condense when they reach their boiling points.
What hydrocarbons will condense higher up the fractional distillation column?
Methane, Ethane etc
What are some fractions used for?
Fuels
What is another way that some fractions are used?
As feedstock (a chemical that is used to make other chemicals) for the petrochemical industry e.g. solvents, lubricants
due to the high demand for short chain hydrocarbons to be used as fuels because they are more flammable, for example, how do you convert long chain hydrocarbons into shorter chain hydrocarbons?
A process called cracking, where a long chain alkane is broken down (cracked) to produce smaller, more useful molecules
What is catalytic cracking?
We use high temperature and a catalyst. The job of the catalyst is the speed up the reaction.
What is steam cracking?
We use high temperature and steam
Property of an alkene?
have a double covalent bond between two carbon atoms
e.g. H H
C — C (two lines)
H H
why are alkenes useful?
they are used to make chemicals called polymers
what is the difference between alkenes and alkanes?
Alkenes are more reactive than alkanes
How to test for alkanes?
using bromine water, which is orange. if we shake our alkene with bromine water, then the bromine water turns colourless
Which hydrocarbons have lower boiling points?
Those with a lower chain of hydrocarbon molecules