| Date | May 2019 | Marks available | 2 | Reference code | 19M.3.sl.TZ2.5 |
| Level | SL | Paper | 3 | Time zone | TZ2 |
| Command term | Explain | Question number | 5 | Adapted from | N/A |
Question
Polymers have a wide variety of uses but their disposal can be problematic.
Draw a section of isotactic polychloroethene (polyvinylchloride, PVC) showing all the atoms and all the bonds of four monomer units.
The infrared (IR) spectrum of polyethene is given.
Suggest how the IR spectrum of polychloroethene would differ, using section 26 of the data booklet.
Identify a hazardous product of the incineration of polychloroethene.
Explain how plasticizers affect the properties of plastics.
Suggest why the addition of plasticizers is controversial.
Markscheme
correct bonding [✔]
Cl atoms all on same side and alternate [✔]
Note: Continuation bonds must be shown.
Award [1 max] if less than or more than four units shown.
Accept a stereo formula with all atoms and bonds shown.
«strong additional» absorption at 600–800 «cm–1» [✔]
Any one of:
HCl [✔]
Cl2 [✔]
dioxins [✔]
C [✔]
CO [✔]
Any two of:
embedded/fit between chains of polymers [✔]
prevent chains from forming crystalline regions [✔]
keep polymer strands/chains/molecules separated/apart [✔]
increase space/volume between chains [✔]
weaken intermolecular/dipole-dipole/London/dispersion/instantaneous dipoleinduced dipole/van der Waals/vdW forces «between chains» [✔]
increase flexibility/durability/softness [✔]
make polymers less brittle [✔]
leach into foodstuffs/environment
OR
«unknown» health/environmental consequences [✔]
Note: Accept “plasticizers cannot be recycled”.
Examiners report
Quite a few candidates scored at least one mark although most either scored both or none for this polymer structure.
Almost all students who attempted this question received the mark for identifying the correct absorption band.
This was a well answered question, with most candidates identifying at least one method plasticizers affect the properties of plastic.
Many students received a mark for this question although some did not because their answers were too vague.
Syllabus sections
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17M.3.hl.TZ2.3c:
Estimate the atom economy of this first step.
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17M.3.sl.TZ1.10b.ii:
Explain why the difference in their structures affects their melting points.
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17M.3.sl.TZ2.3c.i:
Explain how the structure of plasticizers enables them to soften PVC.
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18M.3.sl.TZ1.4a:
Both of these are thermoplastic polymers. Outline what this term means.
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19M.3.hl.TZ2.5a:
Draw a section of isotactic polychloroethene (polyvinylchloride, PVC) showing all the atoms and all the bonds of four monomer units.
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19M.3.sl.TZ2.5a:
Draw a section of isotactic polychloroethene (polyvinylchloride, PVC) showing all the atoms and all the bonds of four monomer units.
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19M.3.hl.TZ1.4b:
Suggest, giving a reason, how elastomers used for the tyre tread can increase the traction between the tyre and the road.
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17M.3.sl.TZ1.10a:
Below are the IR spectra of two plastics (A and B); one is PETE, the other is low density polyethene (LDPE).
Deduce, giving your reasons, the identity and resin identification code (RIC) of A and B using sections 26 and 30 of the data booklet.
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16N.3.sl.TZ0.6a:
(i) Draw the structure of 2-methylpropene.
(ii) Deduce the repeating unit of poly(2-methylpropene).
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16N.3.sl.TZ0.6b:
Deduce the percentage atom economy for polymerization of 2-methylpropene.
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17M.3.sl.TZ2.3c.ii:
Suggest a reason why nanoparticles can better anchor plasticizers in the polymer.
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17N.3.sl.TZ0.7b.i:
Describe how the structures of LDPE and HDPE affect one mechanical property of the plastics.
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18M.3.hl.TZ1.4c.ii:
Deduce, giving a reason, whether the atom economy of a condensation polymerization, such as this, would be greater or less than an addition polymerization, such as the formation of HDPE.
- 19N.3.hl.TZ0.5b: State and explain why plasticizers are added to polymers.
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18N.3.sl.TZ0.2b.i:
Structures of poly(methyl acrylate), PMA, and Bakelite® are shown.
Suggest, giving reasons, which is the thermoplastic polymer and which is the thermosetting polymer.
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19N.3.sl.TZ0.4a:
Draw a section of an isotactic polypropene polymer chain containing four repeating units.
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18M.3.sl.TZ1.4b.ii:
State one way in which a physical property of HDPE, other than density, differs from that of LDPE as a result of this structural difference.
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18M.3.sl.TZ2.4a:
Sketch four repeating units of the polymer to show atactic and isotactic polypropene.
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17M.3.sl.TZ1.10b.i:
Describe the difference in their structures.
- 19N.3.sl.TZ0.4b: Predict, with a reason, whether isotactic or atactic polypropene has the higher melting point.
- 19N.3.sl.TZ0.4c: Polypropene is a thermoplastic. Outline what is meant by thermoplastic.
- 19N.3.sl.TZ0.4d: Discuss why the recycling of plastics is an energy intensive process.
- 20N.3.sl.TZ0.3b(i): Thermoplastic composites are increasingly replacing thermosets. Suggest one advantage of...
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19M.3.hl.TZ2.5c:
Explain how plasticizers affect the properties of plastics.
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16N.3.sl.TZ0.6c:
(i) Suggest why incomplete combustion of plastic, such as polyvinyl chloride, is common in industrial and house fires.
(ii) Phthalate plasticizers such as DEHP, shown below, are frequently used in polyvinyl chloride.
With reference to bonding, suggest a reason why many adults have measurable levels of phthalates in their bodies.
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19M.3.sl.TZ1.4b:
Suggest, giving a reason, how elastomers used for the tyre tread can increase the traction between the tyre and the road.
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18N.3.hl.TZ0.2b:
Structures of poly(methyl acrylate), PMA, and Bakelite® are shown.
Suggest, giving reasons, which is the thermoplastic polymer and which is the thermosetting polymer.
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18M.3.sl.TZ1.4b.i:
Compare and contrast the structures of HDPE and LDPE.
- 20N.3.sl.TZ0.3c: Explain why phthalates are replaced by other plasticizers in the production of plastics.
- 20N.3.hl.TZ0.3b(iii): Explain why phthalates are replaced by other plasticizers in the production of plastics.
- 20N.3.hl.TZ0.3b(i): Thermoplastic composites are increasingly replacing thermosets. Suggest one advantage of...
- 20N.3.hl.TZ0.3b(ii): Explain how thermoplastics, such as polyvinylchloride, PVC, can be made more flexible by the...
- 20N.3.sl.TZ0.3b(ii): Explain how thermoplastics, such as polyvinylchloride, PVC, can be made more flexible by the...
