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Question 19N.3.sl.TZ0.4

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Date November 2019 Marks available [Maximum mark: 5] Reference code 19N.3.sl.TZ0.4
Level sl Paper 3 Time zone TZ0
Command term Discuss, Draw, Justify, Outline, Predict Question number 4 Adapted from N/A
4.
[Maximum mark: 5]
19N.3.sl.TZ0.4

Polypropene is used to make many objects including carpets, stationery and laboratory equipment.

(a)

Draw a section of an isotactic polypropene polymer chain containing four repeating units.

[1]

Markscheme

 

NOTE: Continuation bonds must be shown.
Ignore square brackets and “n”.
Do not accept one repeating unit in square brackets with a subscript of 4.
Accept condensed structure provided all C to C bonds are shown and CH3 groups on same side.
Accept

Do not accept syndiotactic (alternating orientation of the CH3 groups).

(b)

Predict, with a reason, whether isotactic or atactic polypropene has the higher melting point.

[1]

Markscheme

isotactic «has higher melting point» AND ordered chains pack more closely
OR
isotactic «has higher melting point» AND stronger intermolecular/London/dispersion forces ✔

NOTE: Accept “van der Waals’ forces”/”vdW”.

(c)

Polypropene is a thermoplastic. Outline what is meant by thermoplastic.

[1]

Markscheme

softens when heated «and hardens when cooled» ✔

(d)

Discuss why the recycling of plastics is an energy intensive process.

[2]

Markscheme

Any two of:
collection/transportation of plastic waste ✔
separation of different types «of plastic»
OR
separation of plastic from other materials ✔
melting plastic ✔
processing/washing/cleaning/drying/manufacture of recycled plastic ✔

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