| Date | May 2018 | Marks available | 2 | Reference code | 18M.3.sl.TZ1.3 |
| Level | SL | Paper | 3 | Time zone | TZ1 |
| Command term | Discuss | Question number | 3 | Adapted from | N/A |
Question
Aluminium and high density polyethene (HDPE) are both materials readily found in the kitchen, for example as saucepans and mixing bowls respectively. In these applications it is important that they are impermeable to water.
Both materials are also used in other applications that are more demanding of their physical properties. Carbon nanotubes are often incorporated into their structures to improve certain properties.
Discuss, in terms of its structure, why an aluminium saucepan is impermeable to water.
State the name given to a material composed of two distinct solid phases.
State one physical property of HDPE that will be affected by the incorporation of carbon nanotubes.
Describe how carbon nanotubes are produced by chemical vapour deposition (CVD).
State the property of carbon nanotubes that enables them to form a nematic liquid crystal phase.
Markscheme
«close packed» lattice of metal atoms/ions
no spaces for water molecules to pass though the structure
[2 marks]
composite
[1 mark]
melting point
OR
permeability
OR
density
OR
conductivity
OR
elasticity/stiffness
OR
brittleness/flexibility
OR
«tensile» strength
Accept “colour/transparency”.
[1 mark]
Any three of:
hydrocarbon/carbon-containing gas/compound
mixed with inert gas
heat/high temperature
«transition» metal catalyst
hydrocarbon/carbon compound decomposes to form carbon «nanotubes»
nanotubes form on catalyst surface
Accept “ethanol” or specific hydrocarbons.
Accept “N2”, “H2”, “NH3” or specific inert gases.
Accept temperature or range within 600–800 °C.
Accept specific metals such as Ni, Co or Fe.
[3 marks]
rod shaped molecules
[1 mark]
Examiners report
Syllabus sections
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18M.3.sl.TZ1.3b.i:
State the name given to a material composed of two distinct solid phases.
-
18M.3.sl.TZ2.3a:
ICP-OES/MS can be used to analyse alloys and composites. Distinguish between alloys and composites.
-
17M.3.sl.TZ2.3a:
State the two distinct phases of a composite.
- 16N.3.sl.TZ0.3a: Magnesium oxide, MgO, and silicon carbide, SiC, are examples of ceramic materials. State the...
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18M.3.sl.TZ1.4e:
Suggest why there are so many different ways in which plastics can be classified. HDPE can, for example, be categorized thermoplastic, an addition polymer, having Resin Identification Code (RIC) 2, etc.
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19M.3.hl.TZ1.3a:
Identify the type of bonding in lithium hydride, using sections 8 and 29 of the data booklet.
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19M.3.sl.TZ1.3a(i):
Identify the type of bonding in lithium hydride, using sections 8 and 29 of the data booklet.
- 16N.3.sl.TZ0.3b: Predict the predominant type of bonding for a binary compound AB in which the...
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17M.3.sl.TZ2.3b:
Identify the methods of assembling nanocomposites by completing the table.
- 17N.3.sl.TZ0.4b.ii: At present, composite fillings are more expensive than amalgam fillings. Suggest why a...
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17M.3.sl.TZ1.6a:
Determine the type of bond present in SbBr3, showing your method. Use sections 8 and 29 of the data booklet.
-
19N.3.sl.TZ0.5b(i):
Determine the percentage of ionic bonding in alumina using sections 8 and 29 of the data booklet.
-
18M.3.sl.TZ2.4c:
Civilizations are often characterized by the materials they use.
Suggest an advantage polymers have over materials from the iron age.
-
17N.3.sl.TZ0.4a:
Outline the composition of an alloy and a composite.
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17M.3.sl.TZ1.6b:
Lanthanum has a similar electronegativity to group 2 metals. Explain, in terms of bonding and structure, why crystalline lanthanum bromide is brittle.
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19M.3.hl.TZ2.4d:
Outline how alloys conduct electricity and why they are often harder than pure metals.
Conduct electricity:
Harder than pure metals:
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19M.3.sl.TZ2.4d:
Outline how alloys conduct electricity and why they are often harder than pure metals.
Conduct electricity:
Harder than pure metals:
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20N.3.hl.TZ0.3a:
Outline the two distinct phases of this composite.
-
18N.3.hl.TZ0.2a:
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.
-
18N.3.sl.TZ0.2a:
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.
-
20N.3.sl.TZ0.3a:
Outline the two distinct phases of this composite.
