IBDP Official Exam Material
FREE Past paper Questions by Topic
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Option A: Materials
For HL students only
1a. [2 marks]
Carbon fibre reinforced plastic (CFRP) is a useful composite. Epoxy is a thermoset polymer that is used as a binding polymer when making CFRP.
Outline the two distinct phases of this composite.
Markscheme
carbon fibre reinforcing phase ✔
«in a» matrix phase of epoxy ✔
Award [1 max] for “reinforcing phase «embedded» in a matrix”.
1b. [1 mark]
Thermoplastic composites are increasingly replacing thermosets.
Suggest one advantage of thermoplastic polymers over thermosets.
Markscheme
can be recycled
OR
can be reformed when hot
OR
high impact/chemical/abrasion resistance ✔
OR
can be reformed when hot
OR
high impact/chemical/abrasion resistance ✔
1c. [3 marks]
Explain how thermoplastics, such as polyvinylchloride, PVC, can be made more flexible by the addition of phthalate ester plasticizers.
Markscheme
Any three of:
plasticizers embed/fit between «polymer» chains ✔
keep polymer strands/chains/molecules separated/apart ✔
weaken intermolecular/London/dispersion/attractive/forces/instantaneous induced dipole-induced dipole/forces «between chains» ✔
prevent chains from packing closely/forming regular packing/structure ✔
Accept “van der Waals/vdW” for “London”.
1d. [2 marks]
Explain why phthalates are replaced by other plasticizers in the production of plastics.
Markscheme
Any two of:
readily released into environment
OR
have weak intermolecular forces «rather than covalent bonds between chains» ✔
readily released into environment
OR
have weak intermolecular forces «rather than covalent bonds between chains» ✔
get into biological systems by ingestion/inhalation ✔
interrupt endocrine systems
OR
affect release of hormones
OR
effect development of male reproductive system ✔
OR
affect release of hormones
OR
effect development of male reproductive system ✔
considered carcinogenic
OR
can cause cellular damage ✔
OR
can cause cellular damage ✔
can cause early puberty in females ✔
can cause thyroid effects ✔
can cause asthma ✔
Do not accept just “are a health concern”.
2a. [2 marks]
There has been significant growth in the use of carbon nanotubes, CNT.
Explain these properties of carbon nanotubes.
Markscheme
Excellent strength: defect-free AND rigid/regular 2D/3D ✔
Excellent conductivity: delocalized electrons ✔
Accept “carbons/atoms are all covalently bonded to each other” for M1.
2b. [2 marks]
CNT can act as Type 2 superconductors. Outline why Type 2 superconductors are generally more useful than Type 1.
Markscheme
Any two of:
have higher critical temperatures/Tc «than Type 1»
OR
can act at higher temperatures ✔
have higher critical temperatures/Tc «than Type 1»
OR
can act at higher temperatures ✔
have higher critical magnetic fields/Bc «than Type 1» ✔
less time needed to cool to operating temperature ✔
less energy required to cool down/maintain low temperature ✔
2c. [3 marks]
Explain the role of electrons in superconducting materials in terms of the Bardeen–Cooper–Schrieffer (BCS) theory.
Markscheme
Any three of:
passing electrons «slightly» deform lattice/displace positive ions/cations ✔
electrons couple/form Cooper pairs/condense with other electrons ✔
energy propagates along the lattice in wave-like manner/as phonons ✔
Cooper pair/electron condensate/pair of electrons moves through lattice freely
OR
phonons are «perfectly» elastic/cause no energy loss ✔
OR
phonons are «perfectly» elastic/cause no energy loss ✔
2d. [1 mark]
Alloying metals changes their properties. Suggest one property of magnesium that could be improved by making a magnesium–CNT alloy.
Markscheme
Any of:
ductility ✔
strength/resistance to deformation ✔
malleability ✔
hardness ✔
resistance to corrosion/chemical resistance ✔
range of working temperatures ✔
density ✔
ductility ✔
strength/resistance to deformation ✔
malleability ✔
hardness ✔
resistance to corrosion/chemical resistance ✔
range of working temperatures ✔
density ✔
Do not accept “conductivity”.
3a. [2 marks]
Precipitation is one method used to treat waste water.
Phosphates, PO43-, in waste water can be removed by precipitation with magnesium ions. Ksp of magnesium phosphate is 1.04×10-24.
3Mg2+aq+2PO43-aq→Mg3PO42s
Calculate the maximum solubility of phosphate ions in a solution containing 0.0100 mol dm-3 magnesium ions.
Calculate the maximum solubility of phosphate ions in a solution containing 0.0100 mol dm-3 magnesium ions.
Markscheme
PO43-=KspMg2+3 ✔
<<PO43-=<<1.04×10-240.01003=>>1.02×10-9<<mol dm-3>> ✔
Accept “Ksp=Mg2+3PO43-2” for M1.
Award [2] for correct final answer.
Award [2] for correct final answer.
3b. [2 marks]
Precipitation is one method used to treat waste water.
Zinc, cadmium, nickel, and lead are metal ions which can be removed by precipitation. Explain why waste water is adjusted to a pH of 9−10 to remove these ions by referring to section 32 of the data booklet.
Markscheme
Any two of:
precipitation occurs with a base/carbonate/CO32-/hydroxide/OH- ✔
precipitation occurs with a base/carbonate/CO32-/hydroxide/OH- ✔
OH- is high enough to cause metal hydroxide precipitation at that pH ✔
these ions are slightly acidic/more soluble in acidic conditions ✔
only small amounts of carbonate/hydroxides/anion needed at that pH ✔
solubility products of the hydroxides are very small ✔
Do not accept “hydroxyl” for “hydroxide”.
4a. [1 mark]
Superconductors have no resistance below a critical temperature.
Outline how resistance to electric currents occurs in metals.
Markscheme
electrons collide with cations/positive ions ✔
4b. [2 marks]
Suggest why the resistance of metals increases with temperature.
Markscheme
increased vibrations of «lattice» ions ✔
increased «probability of» collisions «between electrons and cations» ✔
increased «probability of» collisions «between electrons and cations» ✔
NOTE: Accept “increases lattice vibrations” for M1.
4c. [2 marks]
State two differences between Type I and Type II superconductors.
Markscheme
Any two of:
Type I have sharper transitions to superconductivity «than Type II» ✔
Type I have lower critical/operating temperatures «than Type II» ✔
Type I have lower critical magnetic field «strength than Type II» ✔
Type I carry lower currents «than Type II» ✔
Type I are «pure» metals/metalloids AND Type II are alloys/metal oxide ceramics/perovskites/metallic compounds ✔
Type II exist in a mixed state/are partly permeable to the magnetic field AND Type I do not/are not ✔
Type I have sharper transitions to superconductivity «than Type II» ✔
Type I have lower critical/operating temperatures «than Type II» ✔
Type I have lower critical magnetic field «strength than Type II» ✔
Type I carry lower currents «than Type II» ✔
Type I are «pure» metals/metalloids AND Type II are alloys/metal oxide ceramics/perovskites/metallic compounds ✔
Type II exist in a mixed state/are partly permeable to the magnetic field AND Type I do not/are not ✔
5a. [2 marks]
Polybutadiene, used in truck tyres, is a polymer of buta-1,3-diene. The spatial arrangement of atoms in the polymer depends on the type of catalyst used.
Outline two differences between heterogeneous and homogeneous catalysts.
Markscheme
Any two of:
heterogeneous catalyst is in different phase than reactants AND homogeneous catalyst in same phase [✔]
heterogeneous catalyst is in different phase than reactants AND homogeneous catalyst in same phase [✔]
homogeneous catalysts chemically change/react and reformed at end of reaction
OR
reactants adsorb onto heterogenous catalyst and products desorb [✔]
OR
reactants adsorb onto heterogenous catalyst and products desorb [✔]
heterogeneous catalysts are more easily removed than homogenous catalysts [✔]
heterogeneous catalysts can function at higher temperatures [✔]
homogeneous catalysts are «generally» more selective [✔]
homogeneous catalysts offer a broader range of reactions [✔]
Note: Accept “state” for “phase”.
Accept “heterogeneous catalyst provides a surface to activate reaction”.
5b. [2 marks]
Suggest, giving a reason, how elastomers used for the tyre tread can increase the traction between the tyre and the road.
Markscheme
elastomers bend under force «and return to original form when force is released»
OR
elastomers make tyre more flexible [✔]
OR
elastomers make tyre more flexible [✔]
allows greater contact with road [✔]
5c. [2 marks]
Tyre fires emit trace quantities of polychlorinated dibenzofurans and polychlorinated dibenzo-p-dioxin.
Outline, using section 31 of the data booklet, why polychlorinated dibenzofuran is not classed chemically as a dioxin but considered “dioxin-like”.
Markscheme
does not contain heterocyclic ring with 2 oxygen atoms
OR
middle ring has only 1 oxygen atom [✔]
OR
middle ring has only 1 oxygen atom [✔]
produces similar toxic effects to dioxins [✔]
5d. [1 mark]
Classify polybutadiene as either an addition or condensation polymer, giving a reason.
Markscheme
addition AND not two different functional groups reacting
OR
addition AND formed by breaking one bond of the carbon–carbon double bonds
OR
addition AND empirical formula of monomer equals empirical formula of polymer
OR
addition AND no atoms removed/all atoms accounted for/no loss of water/ammonia/inorganic by-product/small molecules
OR
addition AND atom economy/efficiency is 100 %
OR
addition AND there is only one «reaction» product [✔]
OR
addition AND formed by breaking one bond of the carbon–carbon double bonds
OR
addition AND empirical formula of monomer equals empirical formula of polymer
OR
addition AND no atoms removed/all atoms accounted for/no loss of water/ammonia/inorganic by-product/small molecules
OR
addition AND atom economy/efficiency is 100 %
OR
addition AND there is only one «reaction» product [✔]
5e. [1 mark]
State one factor considered when making green chemistry polymers.
Markscheme
Any one of:
high content of raw materials in product/high atom economy [✔]
high content of raw materials in product/high atom economy [✔]
use of low toxic chemicals/catalysts/materials/solvents [✔]
renewable feedstock/raw materials [✔]
use of renewable/clean/low carbon energy source [✔]
high safety standards [✔]
increase energy efficiency [✔]
waste recycling [✔]
Note: Accept other reasonable answers.
6a. [2 marks]
EDTA chelates with Ni2+ (aq).
[Ni(H2O)6]2+ (aq) + EDTA4− (aq) ⇌ [Ni(EDTA)]2− (aq) + 6H2O (l)
Explain how entropy affects this equilibrium.
Markscheme
entropy increases «and the reaction proceeds to the right» [✔]
more species / free molecules are formed
OR
more ways of distributing energy [✔]
OR
more ways of distributing energy [✔]
6b. [1 mark]
State the number of coordinate covalent bonds EDTA forms with Ni2+.
Markscheme
six [✔]
7a. [2 marks]
This question is about global warming.
Describe the effect of infrared (IR) radiation on carbon dioxide molecules.
Markscheme
bond length/C=O distance changes
OR
«asymmetric» stretching «of bonds»
OR
bond angle/OCO changes [✔]
OR
«asymmetric» stretching «of bonds»
OR
bond angle/OCO changes [✔]
polarity/dipole «moment» changes
OR
dipole «moment» created «when molecule absorbs IR» [✔]
OR
dipole «moment» created «when molecule absorbs IR» [✔]
Note: Accept appropriate diagrams.
7b. [1 mark]
Outline one approach to controlling industrial emissions of carbon dioxide.
Markscheme
Any one of:
capture where produced «and store» [✔]
capture where produced «and store» [✔]
use scrubbers to remove [✔]
use as feedstock for synthesising other chemicals [✔]
carbon credit/tax/economic incentive/fines/country specific action [✔]
use alternative energy
OR
stop/reduce use of fossil fuels for producing energy [✔]
OR
stop/reduce use of fossil fuels for producing energy [✔]
use carbon reduced fuels «such as methane» [✔]
increase efficiency and reduce energy use [✔]
Note: Do not accept “planting more trees”.
Accept specific correct examples.
8. [2 marks]
Describe the characteristics of the nematic liquid crystal phase.
Shape of molecules:
Distribution:
Markscheme
Shape of molecules:
linear
OR
rod «shaped» [✔]
linear
OR
rod «shaped» [✔]
Distribution:
no positional order AND «some» directional order [✔]
no positional order AND «some» directional order [✔]
Note: Accept “partly ordered”.
9a. [3 marks]
Metals are extracted from their ores by several methods, including electrolysis and reduction with carbon.
Determine the mass of aluminium, in g, that could be extracted from an appropriate solution by a charge of 48 250 C. Use sections 2 and 6 of the data booklet.
Markscheme
moles of electrons «= 48250 C96500 C mol-1» = 0.5000 «mol» [✔]
moles of aluminium «= 0.5000 mol3» = 0.1667 «mol» [✔]
mass of aluminium «= 26.98 g mol–1 × 0.1667 mol» = 4.50 «g» [✔]
Note: Award [3] for correct final answer.
9b. [2 marks]
Once extracted, the purity of the metal can be assessed using ICP-MS. Suggest two advantages of using plasma technology rather than regular mass spectrometry.
pMarkscheme
Any two of:
larger linear calibration [✔]
larger linear calibration [✔]
«accurate» detection of multiple elements/metals [✔]
«accurate» detection of elements in low concentration [✔]
temperature around 10 000 K atomises/ionises every material [✔]
9c. [2 marks]
Explain the action of metals as heterogeneous catalysts.
Markscheme
Any two of:
reactant(s) adsorb onto active sites/surface [✔]
reactant(s) adsorb onto active sites/surface [✔]
bonds weakened/broken/stretched «in adsorbed reactants»
OR
activation energy lowered [✔]
OR
activation energy lowered [✔]
products desorbed [✔]
Note: Accept “products released” for M3.
9d. [2 marks]
Outline how alloys conduct electricity and why they are often harder than pure metals.
Conduct electricity:
Harder than pure metals:
Markscheme
Conduct electricity:
«delocalized/valence» electrons free to move «under potential difference» [✔]
«delocalized/valence» electrons free to move «under potential difference» [✔]
Harder than pure metals:
atoms/ions of different sizes prevent layers «of atoms/ions» from sliding over one another [✔]
atoms/ions of different sizes prevent layers «of atoms/ions» from sliding over one another [✔]
9e. [1 mark]
Carbon nanotubes are added to metals to increase tensile strength.
Write an equation for the formation of carbon nanotubes from carbon monoxide.
Markscheme
2CO (g) → C (s) + CO2 (g) [✔]
10a. [2 marks]
One way of classifying materials is based on the type of bonding present.
Outline why this type of classification is not entirely satisfactory by using magnesium diboride, MgB2, as an example. Refer to sections 8 and 29 of the data booklet.
Markscheme
Δχ = 0.7 AND average Δχ = 1.7 ✔
bonding between metallic and ionic
OR
more than one type of bonding present
OR
bond type difficult to determine as close to several regions/several types/named bonding types «eg ionic and covalent etc.»
OR
bond is mostly covalent «based on % covalent scale on diagram»
OR
bond has « 0.73.2×100=» 22% ionic character ✔
Accept “EN” for “χ".
Accept “bond is ionic but close to several regions/several types/other named bonding type(s) (eg covalent, metallic and covalent etc.)”.
Do not accept just “bond is ionic”.
Accept any value for % ionic character in range 15–24% or % covalent character in range 76–85%.
If you need the markscheme, including the examiners' reports for each question, and more exam and teaching materials on this topic, contact me through the contact page