| Date | May 2010 | Marks available | 3 | Reference code | 10M.3.sl.TZ2.C4 |
| Level | SL | Paper | 3 | Time zone | TZ2 |
| Command term | State | Question number | C4 | Adapted from | N/A |
Question
Detergents are one example of lyotropic liquid crystals.
State one other example of a lyotropic liquid crystal and describe the difference between lyotropic and thermotropic liquid crystals.
Markscheme
soap / kevlar / fatty acids / lipid bilayer / cellulose / silk proteins / DNA;
lyotropic liquid crystals
solutions that show the liquid-crystal state at certain concentrations;
thermotropic liquid crystals
(pure substances that) show liquid-crystal behaviour over temperature ranges (between the solid and liquid states);
Examiners report
This was probably the best answered question in this option with many candidates being able to state the difference between the two types of liquid crystals, as well as give an example of a substance that can have a lytropic liquid crystal state.
