S2.4 From models to materials
Practice exam-style IB Chemistry questions for From models to materials, aligned with the syllabus and grouped by topic.
Question 1
What is meant by a bonding continuum?
A.
A model in which every substance is classified as exactly one bonding type
B.
A scale used only to rank the melting points of ionic compounds
C.
A range of bonding character between ideal ionic, covalent and metallic models
D.
A sequence of bonds arranged from shortest to longest bond length
Question 2
What is released when a dicarboxylic acid reacts with a diol to form a polyester?
A.
Oxygen
B.
Water
C.
Carbon dioxide
D.
Hydrogen
Question 3
Solid sodium chloride does not conduct electricity, but molten sodium chloride does. What is the best explanation?
A.
Ions are fixed in the solid lattice but mobile in the liquid
B.
Electrons are delocalized only when sodium chloride melts
C.
Covalent bonds break to form neutral molecules in the liquid
D.
The ionic bonds become non-polar at the melting point
Question 4
Why is bronze usually harder than pure copper?
A.
Bronze has a fixed empirical formula with stronger covalent bonds
B.
Copper ions become oppositely charged to tin ions in an ionic lattice
C.
Tin atoms disrupt the regular copper lattice and reduce layer sliding
D.
Tin removes all delocalized electrons from the metallic lattice
Question 5
What is the atom economy for addition polymerization of an alkene to its polymer, assuming the polymer is the desired product?
A.
100%, because all atoms of the monomer appear in the polymer
B.
Less than 100%, because water is eliminated at each linkage
C.
50%, because the C=C bond is converted into a C–C bond
D.
0%, because the monomer is not recovered after reaction
Question 6
Which pair of functional groups can react to form an ester linkage in a condensation polymer?
A.
Amino and amino
B.
Alkene and alkene
C.
Amino and hydroxyl
D.
Carboxyl and hydroxyl
Question 7
What linkage is present in a polyamide backbone?
A.
–COO–
B.
–O–O–
C.
–C=C–
D.
–CONH–
Question 8
Hydrolysis of a condensation polymer is best described as which process?
A.
Monomers join with removal of water
B.
Delocalized electrons become fixed between metal ions
C.
Water breaks covalent linkages in the polymer chain
D.
Alkene double bonds open without forming by-products
Question 9
Define a bonding model.
[1]
State one limitation of classifying all substances as ionic, covalent or metallic.
[1]
Question 10
For a binary compound AB, χA = 0.9 and χB = 3.0. What are Δχ and χ̄ for the bond A–B?
A.
Δχ = 2.1 and χ̄ = 1.95
B.
Δχ = 1.95 and χ̄ = 2.1
C.
Δχ = 3.9 and χ̄ = 2.1
D.
Δχ = 2.1 and χ̄ = 3.9
Question 11
What is the repeating unit formed by addition polymerization of propene, CH2=CHCH3?
A.
[–CH=CH(CH3)–]n
B.
[–CH2–CH(CH3)–]n
C.
[–CH(CH3)–CH(CH3)–]n
D.
[–CH2–CH2–CH3–]n
Question 12
Poly(chloroethene), PVC, generally has stronger attractions between chains than polyethene. What structural feature best explains this?
A.
PVC contains mobile chloride ions along the polymer chain
B.
Polyethene chains contain no covalent bonds
C.
Polar C–Cl bonds in PVC allow dipole–dipole attractions between chains
D.
PVC has metallic bonding between neighbouring chains
Question 13
What small molecule is eliminated when a diacyl chloride reacts with a diamine to form a polyamide?
A.
Water
B.
Ammonia
C.
Chlorine
D.
Hydrogen chloride
Question 14
What general statement about biological macromolecules is consistent with the HL syllabus content?
A.
They form only by addition polymerization of alkenes
B.
They form by condensation reactions and break down by hydrolysis
C.
They contain metallic bonding between monomer units
D.
They break down by eliminating hydrogen chloride
Question 15
The electronegativities of magnesium and sulfur are 1.3 and 2.6 respectively.
Calculate Δχ for the Mg–S bond.
[1]
Calculate χ̄ for the Mg–S bond.
[1]
Suggest whether the bond would be placed closer to the ionic or covalent region of the bonding triangle.
[1]
Question 16
Explain why an ionic crystal is usually brittle but a metal is usually malleable. [3]
Question 17
State why alloys are described as mixtures rather than compounds.
[1]
Explain why many alloys are less malleable than the pure metal.
[1]
Question 18
Chloroethene has the structure CH2=CHCl.
Draw the repeating unit of poly(chloroethene).
[1]
State the change in bonding at the carbon atoms during the polymerization.
[1]
Question 19
Describe three common properties of plastics in terms of their polymer structure. [3]
Question 20
Define condensation polymerization.
[1]
State two possible small molecules eliminated in condensation polymerization.
[1]
Question 21
A diacyl chloride reacts with a diol to form a condensation polymer.
State the type of polymer formed.
[1]
State the small molecule eliminated.
[1]
Question 22
The table compares selected properties of polyethene, poly(chloroethene) and polystyrene.
| Polymer | Side group | Relative density | Conductivity | Softening temp / °C |
|---|---|---|---|---|
| Polyethene | H | 0.91–0.97 | Very low | 110–135 |
| Poly(chloroethene) | Cl | 1.30–1.45 | Very low | 75–90 |
| Polystyrene | C6H5 | 1.04–1.07 | Very low | 95–105 |
Identify the polymer with the highest softening temperature in the table.
[1]
Compare the intermolecular forces expected in polyethene and poly(chloroethene).
[1]
Suggest why polystyrene is more brittle than polyethene.
[1]
Question 23
Which structural feature would most likely increase the biodegradability of a plastic?
A.
Hydrolysable ester linkages in the polymer backbone
B.
Very low surface area and high chemical inertness
C.
A fully saturated carbon-chain backbone with no functional groups
D.
Extensive crosslinking that prevents chain access
Question 24
Which monomer could polymerize with itself by condensation to form a polyamide-like chain?
A.
HOCH2CH2OH
B.
H2NCH2COOH
C.
CH3COOH
D.
CH2=CH2
Question 25
A polymer repeat contains the linkage –O–CH2–CH2–O–CO–C6H4–CO–. What type of condensation polymer is represented?
A.
A metallic alloy, because it contains a repeating lattice
B.
An addition polymer, because no atoms are eliminated
C.
A polyester, because the repeat contains ester linkages
D.
A polyamide, because the repeat contains peptide linkages
Question 26
A polymer has the repeating unit [–CH2–C(CH3)2–]n.
Deduce the structure of the alkene monomer.
[1]
Explain why no small molecule is formed in this polymerization.
[1]
Question 27
Define biodegradation of a plastic.
[1]
Distinguish biodegradation from formation of microplastics.
[1]
Question 28
Ethane-1,2-diol, HOCH2CH2OH, reacts with ethanedioic acid, HOOCCOOH, to form a polyester.
State the linkage formed.
[1]
Draw one repeating unit of the polyester.
[1]
Question 29
Hexane-1,6-diamine, H2N(CH2)6NH2, reacts with butanedioic acid, HOOC(CH2)2COOH, to form a polyamide.
State the linkage formed.
[1]
Write the formula of the small molecule eliminated.
[1]
Identify the two residues present in the repeating unit.
[1]
Question 30
Explain why hydrolysis is described as the reverse of condensation polymerization. [2]
Question 31
Polysaccharides are biological macromolecules formed from monosaccharides.
Name the linkage between sugar units.
[1]
Outline how the linkage forms.
[1]
State the reaction type by which polysaccharides break down.
[1]
Question 32
The table gives electronegativity data for several binary substances.
| Substance | Bond considered | χ atom 1 | χ atom 2 |
|---|---|---|---|
| Magnesium oxide, MgO | Mg–O | 1.31 | 3.44 |
| Carbon dioxide, CO₂ | C–O | 2.55 | 3.44 |
| Sodium chloride, NaCl | Na–Cl | 0.93 | 3.16 |
| Silicon, Si | Si–Si | 1.90 | 1.90 |
Determine Δχ and χ̄ for one metal oxide shown in the table.
[1]
Identify the substance expected to have the greatest ionic character.
[1]
Suggest one physical property expected for the substance in (b), with a reason.
[1]
Question 33
The graph shows Vickers hardness, HV, for iron alloys containing different mass percentages of carbon.
Describe the trend shown by the data.
[1]
Explain the trend in terms of metallic bonding and lattice structure.
[1]
Suggest one possible disadvantage of increasing carbon content in a steel used for bridge cables.
[1]
Question 34
The graph shows percentage mass remaining for three plastic films during composting.
Identify the film that degrades fastest.
[1]
Describe one feature of the data that supports your answer to (a).
[1]
Suggest two structural features that could explain faster biodegradation of this film.
[1]
Question 35
The table shows repeat-unit formulae and molar masses for two condensation polymers and their monomers.
| Polymer | Repeat unit fragment | Monomer 1 (M / g mol^-1) | Monomer 2 (M / g mol^-1) | Sum of monomers (g mol^-1) | Repeat unit (g mol^-1) |
|---|---|---|---|---|---|
| A | –O–CH2–CH2–O–CO–C6H4–CO– | HO–CH2–CH2–OH (62.1) | HOOC–C6H4–COOH (166.1) | 228.2 | 192.2 |
| B | –NH–(CH2)6–NH–CO–(CH2)4–CO– | H2N–(CH2)6–NH2 (116.2) | HOOC–(CH2)4–COOH (146.1) | 262.3 | 226.3 |
Identify which polymer is a polyester.
[1]
Determine the small molecule eliminated for the polyester.
[1]
Explain how the mass of the repeat unit provides evidence for condensation polymerization.
[1]
State one linkage that could be broken during hydrolysis of the polyester.
[1]
Question 36
The table gives four monomers with their functional groups.
| Monomer | Displayed formula | Reactive functional groups |
|---|---|---|
| A | HO–CH₂–CH₂–OH | 2 × hydroxyl, –OH |
| B | HOOC–(CH₂)₄–COOH | 2 × carboxyl, –COOH |
| C | H₂N–(CH₂)₆–NH₂ | 2 × amine, –NH₂ |
| D | CH₃–COOH | 1 × carboxyl, –COOH |
Identify a pair that could form a polyester.
[1]
Identify a pair that could form a polyamide.
[1]
State the linkage formed in each polymer in
[1]
and (b).
[1]
Suggest why a monomer with only one reactive functional group cannot by itself form a long condensation polymer chain.
[1]
Question 37
A polyester repeating unit contains –OCH2CH2OCOC6H4CO–.
Deduce the diol used to make this polymer.
[1]
Deduce the dicarboxylic acid used to make this polymer.
[1]
State the by-product formed when these monomers react.
[1]
Question 38
Compare the atom economy of an addition polymerization with that of a condensation polymerization. [3]
Question 39
The graph compares melting points of potassium halides and silver halides as the halide changes from fluoride to iodide.
Describe the trend for potassium halides.
[1]
Suggest why the potassium halide trend is consistent with an ionic model.
[1]
Evaluate why the silver halide trend is not explained as well by a simple ionic model.
[1]
Question 40
The graph shows the concentration of ester linkages remaining in a polyester sample during hydrolysis at two different pH values.
Describe the effect of pH on the rate of hydrolysis shown.
[1]
Explain what happens to the polymer chain during hydrolysis.
[1]
Suggest why the mechanical strength of the sample decreases during the experiment.
[1]
Question 41
The graph shows tensile strength for a series of polyamide fibres prepared with different average chain lengths.
Describe the relationship between chain length and tensile strength.
[1]
Explain the relationship in terms of intermolecular attractions between chains.
[1]
Suggest one reason why the relationship may level off at high chain length.
[1]
Question 42
Outline how a bonding triangle represents the bonding continuum.
[1]
Discuss how bonding models explain the conductivity, brittleness and melting point of ionic, metallic and covalent network materials.
[1]
Question 43
For a binary compound XY, explain how Δχ and χ̄ are calculated from electronegativity data.
[1]
Evaluate the usefulness and limitations of using the bonding triangle to predict properties of silicon and aluminium chloride.
[1]
Question 44
State two examples of biological macromolecules and the linkage type in each.
[1]
Discuss the role of condensation and hydrolysis reactions in forming and breaking down biological macromolecules.
[1]
Question 45
The table summarizes enzyme hydrolysis experiments on three biological macromolecules.
| Macromolecule | Polymer remaining after 30 min / % |
|---|---|
| Protein | 29 |
| Polysaccharide | 61 |
| Nucleic acid | 44 |
Identify the macromolecule that hydrolyses fastest under the conditions shown.
[1]
State the type of linkage hydrolysed in a protein.
[1]
State the type of linkage hydrolysed in a polysaccharide.
[1]
Evaluate whether the data support the statement that all biological macromolecules hydrolyse at the same rate.
[1]
Question 46
Describe metallic bonding and explain why pure metals are malleable.
[1]
Evaluate the use of alloys and reinforced concrete as examples of materials designed by combining bonding and structure.
[1]
Question 47
Define the terms monomer, polymer and repeating unit.
[1]
Explain how the structure of addition polymers accounts for their common properties, including electrical insulation, softening behaviour and resistance or susceptibility to biodegradation.
[1]
Question 48
State the functional groups required to form a polyester and a polyamide from two different monomers.
[1]
Compare and contrast polyester and polyamide formation, including linkages, by-products and hydrolysis.
[1]
Question 49
hydroxycarboxylic acid has the structure HO–R–COOH. Explain why it can form a condensation polymer by itself.
[1]
Explain how the repeating unit forms and how the polymer could be broken down by hydrolysis.
[1]
Question 50
Outline two structural features that can make a plastic more biodegradable.
[1]
Evaluate the design of a biodegradable condensation polymer for packaging, compared with a typical alkene addition polymer. Include bonding, atom economy, hydrolysis and disposal conditions.
[1]
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