CourseCourseConceptConcept

IB Chemistry SL 2.4 From Models to Materials Questions

Practise bonding classification, alloy structure and polymer chemistry to explain how composition and molecular architecture shape material properties and uses.

Syllabus
First assessment 2025
Course
Chemistry SL
Level
SL

Exam points

  • Use electronegativity difference and average values to classify bonds and estimate percentage ionic character.
  • Place compounds on the bonding triangle to predict material properties or explain mixed bonding.
  • Distinguish an alloy from a composite using the constituents and arrangement of their phases.
  • Explain how size-mismatched alloy atoms distort layers, changing hardness, strength or conductivity.
  • Compare thermoplastics, thermosets and elastomers through cross-links, flexibility and heat response.
  • Relate polymer branching, tacticity or plasticisers to chain packing, melting point and flexibility.
  • Judge plastic uses or end-of-life options from material performance, recycling and biodegradability evidence.
  • Draw addition-polymer repeat units or recover alkene monomers with side-group connectivity intact.

Covered syllabus points

2.4.1—Bonding continuum2.4.2—Bonding triangle2.4.3—Alloys2.4.4—Polymers2.4.5—Addition polymers

Question 1

[Maximum number: 3]

Iron may be extracted from iron (II) sulfide, FeS.

Question (a)

(a)

Iron (II) sulfide, FeS , is ionically bonded.

[ 1 ]

Question (i)

(i)

Suggest why chemists find it convenient to classify bonding into ionic, covalent and metallic.

[ 1 ]

Question (b)

(b)

Explain why the addition of small amounts of carbon to iron makes the metal harder.

[ 2 ]

Question 2

[Maximum number: 1]

Iron(II) sulfide can be produced by heating powdered iron and sulfur together.

Outline why solid iron(II) sulfide is a polar covalent compound. Use sections 9 and 17 of the data booklet.

Question 3

[Maximum number: 2]

Titanium is a transition metal.

Explain why an aluminium-titanium alloy is harder than pure aluminium.

Question 4

[Maximum number: 1]

Iron may be extracted from iron (II) sulfide, FeS.

Iron (II) sulfide, FeS , is ionically bonded.

Suggest why chemists find it convenient to classify bonding into ionic, covalent and metallic.

Question 5

[Maximum number: 3]

Chlorine occurs in Group 7, the halogens.

Question (a)

(a)

Chloroethene, H2C=CHCl\mathrm{H}_{2} \mathrm{C}=\mathrm{CHCl}, the monomer used in the polymerization reaction in the manufacture of the polymer poly(chloroethene), PVC, can be synthesized in the following two-stage reaction pathway.

Stage 1: C2H4( g)+Cl2( g)→ClCH2CH2Cl(g)\quad \mathrm{C}_{2} \mathrm{H}_{4}(\mathrm{~g})+\mathrm{Cl}_{2}(\mathrm{~g}) \rightarrow \mathrm{ClCH}_{2} \mathrm{CH}_{2} \mathrm{Cl}(\mathrm{g})

Stage 2: ClCH2CH2Cl(g)→H2C=CHCl(g)+HCl(g)\quad \mathrm{ClCH}_{2} \mathrm{CH}_{2} \mathrm{Cl}(\mathrm{g}) \rightarrow \mathrm{H}_{2} \mathrm{C}=\mathrm{CHCl}(\mathrm{g})+\mathrm{HCl}(\mathrm{g})

[ 3 ]

Question (i)

(i)

State one use of the plastic PVC.

[ 1 ]

Question (ii)

(ii)

Suggest why monomers are often gases or volatile liquids whereas polymers are solids.

[ 2 ]

Question 6

[Maximum number: 3]

Phenylethene (styrene) is produced from ethylbenzene in a gas-phase equilibrium.

Figure for Question 6 — IB Chemistry SL

Question (a)

(a)

Complete the diagram to show the repeating unit of polystyrene.

Figure for Question (a) — IB Chemistry SL
[ 2 ]

Question (b)

(b)

State the type of polymerization that occurs.

[ 1 ]
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