Revision topic 13 Flashcards
what is cracking
it is the processes where large hydrocarbons get broken down into smaller hydrocarbons
how does cracking work
the process takes place at an oil refinery in a steel vessel called the cracker, in the cracker, a heavy fraction distilled from crude oil is heated to vaporize the hydrocarbon, the vapor is either passed over a hot catalyst or is mixed with steam and heated at very high temperature making the hydrocarbon crack into smaller use full chains as thermal decomposition takes place
what is alkene
it is unsaturated hydrocarbons that have double bonds in between their carbons with a formula of C(n)H(2n)
what is the positive test for unsaturated hydrocarbons
bromine water turns colourless
what are the uses of Poly(ethene)
carrier bags, drink bottles, and dustbins
what are the uses of Poly(propene)
carpets, milk carts, ropes
what is polymerization
it is the processes of making polymers where the double bond between the carbons in alkene open up and is replaced by a single bond as thousands of other molecules join together
the properties of a polymer depend on?
- the monomers used to make it
2. the conditions chosen to carry out the reactions
compare low-density monomers to high-density monomers
low-density forms from high pressure and a trace of oxygen where chains are randomly placed and they cannot be packed closely
high-density forms from catalysts at 50c and slightly raised pressure have straighter chains that can be backed more closely giving it a higher softening temperature and is stronger than low density
what are thermosoftening polymers and thermosetting polymers
Thermosoftening polymers are polymers that would soften quite easily but return to their original shape, Thermosoftening polymers have tangled chains and it has week intermolecular bonds, while thermosetting polymers have strong covalent cross-links in between them that give them a high melting point
what are biodegradable
substances that can be broken down by microganisims
how we make a polymer more biodegradable
by making it out of starch for the decomposers to feed on it
