Oils, Earth and Atmosphere Flashcards
What type of reaction is cracking?
A thermal decomposition reaction
Describe the process of cracking.
the long-chain hydrocarbon is heated so it turns into vapour. The vaporised hydrocarbon is then passed over a powdered catalyst at very high temperatures.
The long chain hydrocarbon will ‘crack’ on the surface of the catalyst.
What are the products of cracking ?
Alkanes and Alkenes
Give the chemical formula of an ALKANE?
CnH2n+2
What makes an alkene different from alkane?
Alkenes have double bonds between two of the carbon atoms in their chain.
Alkenes are unsaturated because they can make more bonds by opening up their double bond which allows them to join with other atoms.
What is the general formula for an alkene?
CnH2n
How can we test for an alkene in a substance?
By adding the alkene in a substance called Bromine water. The water will turn from orange to colourless if an alkene is present, this is because the double bond has opened up and formed bonds with the bromine.
Ethene is a product of cracking, what can ethene be used to make?
Ethanol
Describe the process of making Ethanol with Ethene.
Ethene is hydrated with steam in the presence of a catalyst to make Ethanol.
Give the pro’s and Cons of making Ethanol this way.
PRO’S
Cheap process (at the moment)
Ethene is fairly cheap
Not much wasted
CONS
Ethene is produced from crude oil which is non-renewable, it could start running out so using ethene to make ethanol will become very expensive.
What other way can we make Ethanol?
Fermentation
Describe how you would make Ethanol using the fermentation process.
Sugar from plants is converted into Ethanol using yeast. Enzymes in the yeast act as a natural catalyst to make this process happen. Another product formed is carbon dioxide.
Give the pro’s and con’s of fermentation.
PRO'S lower temperature simpler equipment then Ethene. renewable source, uses a raw material. can be used as a cheap fuel. CON'S Ethanol produced is not very concentrated, if you wanted to increase its strength you have to distil it. Needs to be purified. If sugar plants are being grown for fuel, there is less being grown for food so food prices will rise.
What is polymerisation?
Polymerisation means joining together lots of small alkene molecules to form very large molecules.
How do we extract oils from plants?
The plant material is crushed.
Then the crushed plant is pressed between metal plates which squashes the oil out.
The oil is then refined using distillation which removes water, solvents and impurities.
What are vegetable oils used for?
Food- healthy Cooking- speed up cooking, oil has a higher boiling point then water so food can be cooked at a higher temperature faster. Also gives a different flavour Increases the energy we get from it. To produce fuels- biodiesal
What are mono unsaturated fats?
fats that contain only one carbon double bond in their long-chain molecule.
what are polyunsaturated fats?
Fats containing more than one carbon double bond.
How can we harden unsaturated vegetable oils?
By reacting them with hydrogen in the presence of a nickel catalyst at 60 degrees. We call this hydrogenation.
The hydrogen reacts with the doubled-bonded carbons and opens out the double bond.
How is margarine made?
It is made from partially hydrogenated vegetable oil, this gives it a nice buttery, spreadable consistency as completely hydrogenating it would make it too hard.
Why are partially hydrogenated vegetable oils used instead of butter?
Cheaper, keep longer.
What is the down side to partially hydrogenated vegetable oils?
They contain trans-fats. Trans-fats increase the amount of cholesterol in the blood.
What are emulsions made up of?
Lots of droplets of one liquid suspended in another liquid. E.G. an oil in water emulsion. Emulsions make a substance thicker.
How do emulsifies help oil and water mix?
Oils and water naturally separate out. Emulsifiers have a hydrophilic head which laches onto the water molecules and a hydrophobic tail which is attracted to the oil and suspends itself into the oil molecule. This prevents the oil and water from separating.
