| Date | May 2016 | Marks available | 2 | Reference code | 16M.3.sl.TZ0.6 |
| Level | SL | Paper | 3 | Time zone | TZ0 |
| Command term | Explain | Question number | 6 | Adapted from | N/A |
Question
Biphenyl nitriles, such as the molecule shown below, were the first thermotropic liquid crystal molecules to be synthesized.
Suggest how changing the size or shape of the hydrocarbon chain would affect the molecule’s liquid crystal behaviour.
[1]
a.
Explain why the nitrile group enables these molecules to be used in liquid-crystal displays (LCDs).
[2]
b.
Markscheme
alters the temperature range of the liquid-crystal state
OR
alters sensitivity «of the liquid crystal» to electric field«s»
OR
prevents liquid crystal activity
a.
«CN group makes» molecule polar
alignment/orientation of molecules can be controlled by electric field
OR
allows molecules to align in an electric field/when a voltage is applied
Accept “CN is polar”.
b.
Examiners report
[N/A]
a.
[N/A]
b.
