9. Other useful substances from Crude Oil Flashcards
What is it called when Hydrocarbons are broken down to form smaller more useful molecules?
Cracking
How does cracking work?
Cracking is a thermal decomposition reaction (breaks molecules down by heating them)
The first step is to heat the long chain and vaporise it
Then pass then vapour over a hot, powdered catalyst at temperatures of about 400’C- 700’C
Aluminium Oxide is frequently used
The long chains spilt apart of the surface of the catalyst
This produces many Alkanes and Alkenes
What are unsaturated Hydrocarbons called?
Alkenes
Alkenes
Alkenes are hydrocarbons with Carbon double bonds
They are known as unsaturated because they can make more bonds, the Carbon double bonds can open up and they can bond with other atoms
What is the general formula of the homologous series of Hydrocarbons called Alkenes?
Cn H2n
1 Carbon
2 Carbons
3 Carbons
Meth
Eth
Prop
What is the name for the alkane with two Carbons?
Ethane
What is the name for the alkene with two Carbons?
Ethene
What happens if you put an alkene in Bromine water?
It turns it form orange to colourless
How is Ethene useful?
It can produce Ethanol, when reacted with steam in the presence of a catalyst
Other than fuels what else can Alkenes be used to produce?
Alkenes can be used to produce polymers such as poly(ethene)
What is polymerisation ?
It is when many small molecules (monomers) join together to form very large molecules (polymers)
The properties of polymers depends of what?
On what they are made of and the conditions under which they are made
for example Low Density polymers and High density polymers are made using different catalysts and reaction conditions
What are Thermosoftening polymers?
Plastics made up of individual, tangled, long chains held together by weak intermolecular forces of attraction
When heated, the chains are free to pass over each other
This means they have a low melting point and are stretchy
What are Thermosetting polymers?
They have strong bond between the polymer chains, these might be covalent bonds between the chains, or cross-linking bridges
The crosslinks hold the chains firmly together
This means they have a very high melting points, are rigid and can’t be stretched
