| Date | May 2018 | Marks available | 2 | Reference code | 18M.3.hl.TZ2.6 |
| Level | HL | Paper | 3 | Time zone | TZ2 |
| Command term | Discuss | Question number | 6 | Adapted from | N/A |
Question
Chemical vapour deposition (CVD) produces multi-walled carbon nanotubes (MWCNT) of a more appropriate size for use in liquid crystals than production by arc discharge.
MWCNT are very small in size and can greatly increase switching speeds in a liquid crystal allowing the liquid crystal to change orientation quickly.
Discuss two other properties a substance should have to be suitable for use in liquid crystal displays.
Markscheme
Any two from:
chemically stable AND does not «chemically» degrade over time
stable over range of temperatures AND to avoid «voltage/random shift» fluctuations
polar AND influenced by an electric field
strong intermolecular forces AND allow molecule to align in specific orientations
Award [1 max] for identifying two correct properties without any discussion given or incorrect interpretation of suitability.
Accept “voltage” for “electric field”.
[2 marks]
