Flashcards in C10: Other Products from Crude Oil Deck (21):
The reaction used to break down large unusable hydrocarbons into smaller, more useful ones.
Conditions for cracking
Passed over a hot catalyst/ mixed with steam
Heated to a high temperature (e.g. 500 degrees)
Unsaturated hydrocarbons which contain carbon-carbon double bonds. General formula CnH2n
Test for alkenes/ unsaturated carbon-carbon double bonded molecules
Bromine water turns from orange to colourless.
A reaction in which water is chemically added to a compound.
What is produced by cracking?
alkanes to be used as fuel, and alkenes.
Small reactive molecules that react together in repeating sequences to form a very large molecule (a polymer).
Properties of poly(ethene)
> Easy to shape
Properties of poly(propene)
When alkene molecules join together as the double bond between the carbon atoms 'opens up' and the thousands of molecules are able to join together.
What do the properties of a polymer depend on?
> The monomers used to make it.
> The conditions chosen to carry out the reaction.
Low Density poly(ethene)
> Formed using high pressure and trace oxygen.
> Polymer chains are joined together at random and they can't pack together, hence its lower density.
High Density poly(ethene)
> Formed using a catalyst at 50 degrees with a slightly raised pressure.
> Creates straight, closely packed chains that give it a higher density.
> It is stronger and less prone to melting that LD poly(ethene).
Polymers that form plastics which can be softened by heating, then remoulded into different shapes as they cool down and set.
Polymers that can form extensive cross-linking between chains, resulting in rigid materials which are heat resistant.
What sort of bonds are used in polymer chains?
Very strong covalent bonds.
Bonding in Thermosoftening Polymers
> Forces between the polymer chains are weak, and broken by heating.
> When the polymer cools down again, it is brought back together by intermolecular forces.
Bonding in Thermosetting Polymers
> Monomers create covalent bonds between the polymer chains when it is forms to create its shape and structure.
> Covalent bonds are strong, and stops the polymer from melting or changing shape.
> Polymer will not melt, will char instead at high enough temps.
Which is more reactive- alkanes or alkenes?
The C-C double bond in alkenes make them much more reactive.
Polymers that change in response to changes in their environment.