C1.5 Other useful substances from crude oil Flashcards
How do you crack hydrocarbons?
heating the hydrocarbons to vaporise them. The vapours are either passed over a hot catalyst (Aluminium Oxide) or mixed with steam and heated to a very high temperature so thermal decomposition can occur.
What are the products of cracking?
- alkanes
- alkenes
what are alkenes?
unsaturated hydrocarbons
what is the general formula for alkenes?
CnH2n
What are the first 2 alkenes?
1) ethene
2) propene
What happens when alkenes are mixed with bromine water? why?
bromine turns from ORANGE to COLOURLESS.
As the double bond has opened up and formed bonds with bromine.
Describe polymerisation
the joining together together of lots of small alkene molecules (monomers) to form very large molecules (polymers)
Describe useful applications of polymers that have been developed
- Packaging materials
- Waterproof coatings for fabrics
- Hydrogels
- Smart materials- shape memory polymers
Why do polymers lead to problems with waste disposal?
Many polymers are not BIODEGRADABLE
so they are not broken down by microbes
so they are taking up valuable room in landfill sites
How are plastic bags being made so they break down more easily?
As well as being made with polymers, they are being made with cornstarch.
Biodegradable plastics made from cornstarch have been developed.
What 2 ways can ethanol be produced?
1) Hydration
2) Fermentation
Describe the process of hydration to make ethanol
Ethanol can be produced by the hydration of ethene with steam in the presence of a catalyst.
Describe the process of fermentation to make ethanol
The raw material for fermentation is sugar. this is converted into ethanol with yeast.
sugar—— carbon dioxide + ethanol
Why are hydrocarbons cracked?
to produce smaller, more useful molecules
What is an advantage of making ethanol from fermentation?
Sugar is a renewable resource.
Ethanol produced this way can be used as a cheap fuel.
Fermentation uses lower temperatures and less equipment than hydration with steam
What is a disadvantage of using fermentation to make ethanol?
Ethanol from fermentation isn’t very concentrated
If you want to increase the concentration, you have to distil it.
What are some advantages of using hydration with ethene to make ethanol?
Cheap process
not much ethene is wasted during the process
alcohol does not need to be distilled
process is continuous
What are some disadvantages of using hydration with ethene to make ethanol?
Ethene’s produced from crude oil, which is non renewable- could start running out.
This means using ethene to make ethanol will become very expensive
name 2 substances produced when poly(ethene) burns in air
Water
carbon dioxide
What is seen when sugar solution and yeast are fermented?
bubbling
Describe in terms of molecules how poly(ethene) is produced
many monomers (ethene molecules) are joined together
Describe how the process of fermentation is done
sugar is mixed with water and yeast is added
Why are biofuels thought to be carbon neutral?
plants to produce biofuel absorb carbon dioxide
which is released when biofuels are burnt
Why is cracking useful in the oil industry?
It produces smaller, more useful molecules
hydrocarbons with large molecules are limited in their usefulness
smaller molecules such as alkenes can be joined up into polymers which make up plastics
Name the type of reaction in which products of fractional distillation are converted into other, more useful substances
cracking
Name the type of reaction in which alkene molecules are joined together
polymerisation
What does saturated mean when describing hydrocarbons?
Carbon atoms have formed as many bonds as possible with hydrogen atoms
there are only single bonds
so no double bonds
Cracking involves heating the ………. to make a vapour. The vapour is then passed over a very hot ……………. or mixed with steam
alkenes
catalyst
Describe what happens in a polymerisation reaction
many monomers are joined together to form a polymer
What are some environmental advantages and disadvantages of reusing plastic bags?
- saves crude oil
- saves energy
- cuts down on carbon dioxide emissions so less global warming
- could cause litter
What are some environmental advantages and disadvantages of recycling plastic bags by melting and making them into new plastics?
- used to make new objects
- saves crude oil
- cuts down on carbon dioxide emissions so less global warming
- melting requires energy- uses fossil fuel
- transportation to recycle uses petrol— global warming
What are some environmental advantages and disadvantages of burning plastic bags to release energy?
- could provide energy for heating buildings or for generating electricity
- increases carbon dioxide emissions— carbon dioxide
- could release toxic gases
Suggest a property of a smart polymer that is different to that of an ordinary polymer
has a shape memory
What is hydration?
a reaction with steam/water
Explain how solid waste yeast is removed from a solution
filter
Explain how ethanol is obtained from a solution
distillation
Suggest why air must not enter the reactor during a cracking reaction
as oxygen could react with the hydrocarbons
