Polymerisation

Question 1

Alkenes under go what?

Answer 1

• polymerisation to produce saturated chains ( alkanes )

* a pi bond is broken and 2 new sigma bonds are made

Question 2

How is a sigma bond formed?

Answer 2

• when 2 s orbitals overlap
- they overlap in a straight line which gives the highest possible electron density between 2 nuclei : this is a covalent bond

Question 3

How is a pi bond formed?

Answer 3

• when to p orbitals overlap

Question 4

Why are alkenes much more reactive than alkanes?

Answer 4

• the C=C double bond has a high electron density which makes it reactive
• because the pi bond sticks out above / below the rest of the molecule it’s easier for the pi bond to be attacked by electrophiles

Question 5

Problem with plastics?

Answer 5

• products are resistant to chemicals so they do not break down naturally - non biodegradable
• makes it difficult to dispose of
• as more non biodegradable materials pile up there’s an increased threat to the environment

Question 6

Ways to get rid of waste?

Answer 6

1. Recycling : because many plastics are made from non renewable oil fractions - makes sense to recycle them
   - after sorting ( which can be a problem ) some plastics can be
   • remoulded
   • cracked into monomers and can be used to make more plastics or other chemicals
2. Waste plastics can be burned ;
   - the heat can be used for electricity
   - process needs to be controlled to reduce toxic gases
   - CO is poisonous formed by ICC
   Solution: supply more O2 for CC to CO2
   • Chlorine containing polymers burn to produce HCI = corrosive/toxic
   Solution: chemists remove HCI before it’s released in air by reacting it with a base, bubbling through water it dissolving it in water to make it more dilute or use of gas scrubber

Question 7

Increasing sustainability?

Answer 7

Feedstock recycling :
- chemists can develop processes to convert polymers into chemicals which can be fed directly into the processes for manufacturing useful products such as fuel and even more polymers

New generation of plastics:
- chemists develop bio plastics from renewable raw materials e.g starch, maize, cellulose and lactic acid. They’re made using hazard free processes and kinder to environment when disposed of as they degrade naturally to CO2 + H2O due to bacterial activity in soil.

Question 8

Advantages of using renewable raw materials?

Answer 8

• aren’t going to run out
• when they biodegrade, CO2 produced
• some plant based polymers save energy compared to oil based plastics

Question 9

What are polymers?

Answer 9

• long chained molecules joined by many small chained molecules called monomers