4.5.4 - alkenes

Question 1

how can you tell if its an alkene rather than an alkane

Answer 1

it has a double bond ( = )

Question 2

general formula of alkenes

Answer 2

CnH2n

Question 3

alkenes are a homologous family which have:

Answer 3

• similar chemical reactions
• trends in physical properties (eg. boiling points, viscosity or colour)
• the same general formula

Question 4

why are alkenes referred to as unsaturated

Answer 4

they have a C=C double bond

Question 5

what do alkenes react with to break the C=C double bond

Answer 5

bromine

Question 6

what happens in an alkene reaction with bromine

Answer 6

the C=C breaks (into C-C) and the Br atoms add in

Question 7

what type of reaction is the reaction between alkenes and bromine

Answer 7

addition reaction - because your adding the bromine atoms into the alkene

Question 8

what does the reaction between alkenes and bromine happen without

Answer 8

UV light - because alkenes are more reactive than alkanes

Question 9

what does the reaction between alkenes and bromine work with

Answer 9

pure bromine liquid or bromine water (reaction goes orange -> colourless)

Question 10

how does an addition polymer form

Answer 10

when molecules with a C=C double bond add into chains

Question 11

formation of addition polymers:

Answer 11

• the small molecules that add together are called monomers
• the long chain they form when added together is called a polymer

Question 12

how is the name of an addition polymer formed

Answer 12

by putting ‘poly’ in front of the monomer name

eg. the polymer formed by ‘ethene’ would be called ‘poly(ethene)’

Question 13

commonly encountered polymers

Answer 13

• poly(ethene)
• poly(propene)
• poly(chloroethene)
• poly(tetrafluoroethene)

Question 14

uses of poly(ethene)

Answer 14

• drinks bottles
• shopping bags

Question 15

uses of poly(propene)

Answer 15

• storage boxes
• climbing ropes

Question 16

uses of poly(chloroethene)

Answer 16

• wire insulation
• drainpipes

Question 17

uses of poly(tetrafluoroethene)

Answer 17

• non-stick coating

Question 18

why are there disposal issues with addition polymers

Answer 18

• they are intert, meaning they are chemically very unreactive
• this means they don’t break down easily

Question 19

options for disposal of addition polymers:

Answer 19

• REUSE IT, or give it to someone who will use it
• RECYCLE IT, which allows it to be reshaped for another use
• INCINERATE IT, and use the energy released to generate electricity
• CHUCK INTO LANDFILL, and hope it goes away