What is cracking?
Splitting long chained hydrocarbons
What does cracking produce?
Some useful fuels
→ Most of the products of cracking are alkAnes
What sort of reaction is cracking?
A thermal decomposition reaction (breaking molecules down by heating them)
How is cracking done?
- Heat the long chained hydrocarbon to vapourise it
- The vapour is then passed over a powdered catalyst at a temperature of about 400℃ - 700℃
- The catalyst is Aluminium Oxide
What are alkenes?
Hydrocarbons which have a double bond between two of the carbon atoms in their chain
Are alkenes saturated or unsaturated?
Unsaturated because that can make more bonds (the double bond can open uo allowing the two carbon atoms to bond with other atoms)
What are the first 2 alkenes?
Ethene and propene
General formula of alkEnes?
How can you test fo alkenes? (double bonds)
B adding the substance to bromine water
An alkene will decolourise the bromine water, turning it from orange to colourless
This isbecause the double bond has opened up and formed bonds with the bromine
How can ethanol be made?
Hydrating ethene with steam in the prescence of a catalyst
good things about production of ethanol but bad things?
- At the moment its cheap (because the ethene is cheap and not much is wasted)
- However, ethene is produces from crude oil which is non-renewable that will run out, which will make it more expensive
How can ethanol be produced from renewable sources?
Sugar is converted to ethanol by fermentation
sugar → carbon dioxde + ethanol
Advantage of producing ethanol from renewable sources?
The process needs a lower temperature and simpler equipment
Raw material is renewable
Ethanol can be used as a cheap fuek in countries which don't have oil reserves for making petrol
isadvantages of making ethanol from renewable sources?
The ethanol from this process isn't very concentrated
→ So if you want to incease its strength you have to distil it
It also needs to be purified
How can alkenes be used to make polymers?
→ The joining together of small alkene molecules (monomers) to from very large molecules - polymers
What is the product called when many ethene molecules are joined up/?
What does the propertes of polymers depend on?
What its made from
The pressure and temperature at which it was made in polymerisation