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CHEMISTRY, M7 2025 HSC 28

Kevlar and polystyrene are two common polymers.

A section of their structures is shown.
 

     

  1. Kevlar is produced through a reaction of two different monomers, one of which is shown. Draw the missing monomer in the box provided.   (1 mark)

  1. Kevlar chains are hard to pull apart, whereas polystyrene chains are not.
  2. With reference to intermolecular forces, explain the difference in the physical properties of the two polymers.   (3 marks)

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a.    
           

b.    The physical differences between the two polymers are:

  • Kevlar chains are very hard to pull apart because the polymer contains many amide groups that can form strong hydrogen bonds between neighbouring chains. These strong forces hold the chains tightly together, making Kevlar rigid and very strong.
  • The close packing of the chains also gives Kevlar a high melting point, because a large amount of energy is required to break the hydrogen bonds.
  • Polystyrene, on the other hand, does not contain groups that can form hydrogen bonds. Its polymer chains are mostly non-polar, so the only forces between the chains are weak dispersion forces.
  • These weaker attractions mean the chains can slide past each other, making polystyrene much softer, brittle, and it also has a lower melting point than Kevlar. Because the forces between chains are weak, polystyrene is much easier to pull apart compared to Kevlar.
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a.    
           

b.    The physical differences between the two polymers are:

  • Kevlar chains are very hard to pull apart because the polymer contains many amide groups that can form strong hydrogen bonds between neighbouring chains. These strong forces hold the chains tightly together, making Kevlar rigid and very strong.
  • The close packing of the chains also gives Kevlar a high melting point, because a large amount of energy is required to break the hydrogen bonds.
  • Polystyrene, on the other hand, does not contain groups that can form hydrogen bonds. Its polymer chains are mostly non-polar, so the only forces between the chains are weak dispersion forces.
  • These weaker attractions mean the chains can slide past each other, making polystyrene much softer, brittle, and it also has a lower melting point than Kevlar. Because the forces between chains are weak, polystyrene is much easier to pull apart compared to Kevlar.

CHEMISTRY, M7 2024 HSC 22

Vinyl fluoride can be polymerised.
 

In the box provided, draw the structural formula for a six-carbon section of the polymer formed from the polymerisation of vinyl fluoride.   (2 marks)

 

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CHEMISTRY, M7 EQ-Bank 27

Contrast ONE addition polymer and ONE condensation polymer in terms of their structures, properties and uses. Include structural formulae in your answers.   (7 marks)

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Addition polymer – polyethylene. Condensation polymer – nylon.

Structures

  • Polyethylene is made by the addition of ethylene monomers with the following structural formula:

  • Nylon is a condensation polymer made from 1,6-diaminohexane and adipic acid, producing a by-product of water molecules. It has the following structural formula.

Properties

  • Polyethylene is inexpensive, weatherproof and relatively resistant to chemicals.
  • There are two main types of polyethylene which have different properties. Low-density polyethylene (LDPE) is semi-rigid while high density polyethylene (HDPE) is fluid.
  • Nylon is strong and relatively resistant to moisture absorptivity. It is longer lasting than polyethylene, resistant to chemicals and is used to make nylon fibre.

Applications

  • LDPE is used to produce products such as plastic soft drink bottles, flexible water pipes and cling wrap. HDPE’s fluidity make it an appropriate material for producing shopping bags, plastic crates and drums for storage.
  • Nylon is very versatile in its manufacturing uses. It is a common input for clothing, can be used for injection-moulded parts for vehicles and also as reinforcement for rubber tyres. 
  • Nylon is also used as the main material input for nylon thread which has a myriad of uses, including stitching for clothes and the production of rope.
Show Worked Solution

Addition polymer – polyethylene. Condensation polymer – nylon.

Structures

  • Polyethylene is made by the addition of ethylene monomers with the following structural formula:

  • Nylon is a condensation polymer made from 1,6-diaminohexane and adipic acid, producing a by-product of water molecules. It has the following structural formula.

Properties

  • Polyethylene is inexpensive, weatherproof and relatively resistant to chemicals.
  • There are two main types of polyethylene which have different properties. Low-density polyethylene (LDPE) is semi-rigid while high density polyethylene (HDPE) is fluid.
  • Nylon is strong and relatively resistant to moisture absorptivity. It is longer lasting than polyethylene, resistant to chemicals and is used to make nylon fibre.

Applications

  • LDPE is used to produce products such as plastic soft drink bottles, flexible water pipes and cling wrap. HDPE’s fluidity make it an appropriate material for producing shopping bags, plastic crates and drums for storage.
  • Nylon is very versatile in its manufacturing uses. It is a common input for clothing, can be used for injection-moulded parts for vehicles and also as reinforcement for rubber tyres. 
  • Nylon is also used as the main material input for nylon thread which has a myriad of uses, including stitching for clothes and the production of rope.

CHEMISTRY, M7 2018 HSC 21

Ethylene can be readily transformed into many useful products.

  1. What is the name of the industrial process by which ethylene is obtained from long chain alkanes?   (1 mark)

  2. Ethylene can be converted into vinyl chloride.
  3. Draw structural formulae for vinyl chloride and its polymer, polyvinyl chloride.   (2 marks)

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a.   Cracking

b.   Vinyl chloride:


      

Polyvinyl chloride:
 
     

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a.   Cracking

b.   Vinyl chloride:


      

Polyvinyl chloride:
 
     

CHEMISTRY, M7 2016 HSC 17 MC

A polymer has the following structure.
 

Which of the following represents the monomer from which this polymer can be produced?
 

 

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`D`

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  • Break the polymer at every second \(\ce{C–C}\) bond (yields identical sections)
  • Adjust single carbon bond to \(\ce{C=C}\) bond in monomer

`=>D`

CHEMISTRY, M7 2016 HSC 4 MC

Which row of the table correctly identifies an application of polystyrene and the reason for its suitability for that application?
 

  Application Reason for suitability
A.    Shopping bags Rigidity
B. Shopping bags Flexibility
C. Screwdriver handles Rigidity
D. Screwdriver handles Flexibility
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`C`

Show Worked Solution
  • Polystyrene is used to make stiff and durable plastics vs polyethylene that produces flexible and transparent  plastic products.

`=>C`

CHEMISTRY, M7 2015 HSC 25b

Explain the uses of polyethylene and polystyrene in terms of their structures and properties.   (4 marks)

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Polyethylene:

  • Polyethylene consists of long carbon chains with numerous branches but with no side groups.

  • The branches do not allow the long chains to pack closely together and the weak dispersion forces between chains make it flexible, transparent and soft.
  • These characteristics make polyethylene a great material for making cling-wrap and milk bottles. 

Polystyrene:

  • Polystyrene consists of long carbon chains with benzene rings attached to alternative carbon atoms along the chain.

  • The benzene rings create a much stiffer and hardier material with excellent heat insulation and water resistant properties.
  • Polystyrene can be used for screwdriver handles and car battery cases, as well as packaging white goods and other electrical products that can be ruined by water damage.
Show Worked Solution

Polyethylene:

  • Polyethylene consists of long carbon chains with numerous branches but with no side groups.

  • The branches do not allow the long chains to pack closely together and the weak dispersion forces between chains make it flexible, transparent and soft.
  • These characteristics make polyethylene a great material for making cling-wrap and milk bottles. 

Polystyrene:

  • Polystyrene consists of long carbon chains with benzene rings attached to alternative carbon atoms along the chain.

  • The benzene rings create a much stiffer and hardier material with excellent heat insulation and water resistant properties.
  • Polystyrene can be used for screwdriver handles and car battery cases, as well as packaging white goods and other electrical products that can be ruined by water damage.

CHEMISTRY, M7 2015 HSC 25a

Describe the steps involved in the process of addition polymerisation.   (3 marks)

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Step 1:

  • An organic peroxide (initiator – `text{I}`) attacks the ethylene molecule, breaking its double bond and forming a free radical.
  • An unpaired reactive electron can be seen on the end of the growing chain (initiation).

Step 2:

  • The free radical will then attack another ethylene molecule, increasing the length of the growing polymer chain (propagation).

Step 3:

  • Chain length increases in this fashion until two growing chains combine (termination).
Show Worked Solution

Step 1:

  • An organic peroxide (initiator – `text{I}`) attacks the ethylene molecule, breaking its double bond and forming a free radical.
  • An unpaired reactive electron can be seen on the end of the growing chain (initiation).

Step 2:

  • The free radical will then attack another ethylene molecule, increasing the length of the growing polymer chain (propagation).

Step 3:

  • Chain length increases in this fashion until two growing chains combine (termination).

♦ Mean mark 50%.

CHEMISTRY, M7 2017 HSC 12 MC

What is the product when propene undergoes addition polymerisation?
 


 
 

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`D`

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Polymerisation of propene:

  • No double bonds (eliminate A and C)
  • Methyl functional group appear on every second carbon atom

`=>D`


♦ Mean mark 43%.

CHEMISTRY, M7 2019 HSC 13 MC

A sample of polydifluoroethylene is determined to have an average molar mass of  4.8 × 104 g mol ¯1.

Approximately how many carbon atoms are there in an average molecule?

  1. 750
  2. 1500
  3. 2500
  4. 4000
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`B`

Show Worked Solution
  • \( \ce{Polydifluoroethylene: C2F2H2} \)
  • \( \text{MM} (\ce{C2F2H2}) = 64.036\ \text{g}\)
   `text{N (repeating units)}` `=(text{MM (total sample)})/(text{MM (repeating sample)})`  
  `=(4.8 xx 10^4)/64.036`  
  `=750\ text{carbons per repeating unit}`  
  `=1500\ text{carbons (2 per repeating unit)}`   

 
`=>B`


♦ Mean mark 50%.