cracking and polymerisation

Question 1

what is cracking

Answer 1

cracking involves the breaking down of larger saturated hydrocarbon molecules (alkanes) into smaller, more useful ones, some of which are unsaturated (alkenes)

Question 2

describe the process of cracking

Answer 2

1) long molecules, which are not very useful, are broken down by heating them.
2) cracking produces shorter chain alkanes, which are useful as fuels
3) cracking also produces alkenes, which are used to make polymers

Question 3

Describe the cracking of liquid paraffin in the laboratory

Answer 3

paraffin is an alkane. it can be cracked in the lab.

1) the porous pot is heated strongly
2) the liquid paraffin is heated and evaporates
3) the paraffin vapour passes over the hot porous pot and the hydrocarbon molecules break down.
4) one of the products is ethene, which is a gas and collects in the other tube.

Question 4

why is cracking necessary

Answer 4

because there is more demand for specific products

Question 5

what is a polymerisation reaction

Answer 5

joining together of lots of monomers to form very large molecules- these long-chain molecules are called polymers.

Question 6

describe a polymerisation reaction of ethene

Answer 6

lots of ethene molecules can be made yo join up to form one long molecule called poly(ethene). the poly(ethene) only has single bonds between carbon atoms.

Question 7

what are small molecules called in polymerisation

Answer 7

monomers. lots of monomers join up to make polymers

Question 8

what is biodegradability

Answer 8

materials eventually rot away because microbes feed on them and break them down

Question 9

are polymers biodegradable, and is this useful

Answer 9

most polymers are not biodegradable. this is useful, because products made from them last a long time. it is also a problem because when polymers have been thrown away they do not rot.

Question 10

give 2 problems of disposing polymers

Answer 10

polymers are not biodegradable, they last for many years, we are running out of landfill sites. also burning polymers releases toxic gases.

Question 11

give 2 good ways of disposing polymers

Answer 11

by recycling, melting or breaking down polymers to make new products, by developing biodegradable polymers which will rot away in landfill sites.