Question 19M.3.sl.TZ1.7d
| Date | May 2019 | Marks available | [Maximum mark: 2] | Reference code | 19M.3.sl.TZ1.7d |
| Level | sl | Paper | 3 | Time zone | TZ1 |
| Command term | Explain | Question number | d | Adapted from | N/A |
Starch is a natural polymer of glucose.
Explain how the inclusion of starch in plastics makes them biodegradable.
[2]
Any two of:
carbohydrate grains swell/break plastic into smaller pieces [✔]
inclusion of carbohydrate makes the plastic more hydrophilic/water soluble [✔]
carbohydrates are broken down/hydrolysed/digested by bacteria/micro-organisms [✔]
plastic becomes more accessible to bacteria as holes/channels are created in it [✔]
«presence of» carbohydrate weakens intermolecular/London/dispersion forces between polymer chains in the plastic [✔]
Note: Accept “starch” for “carbohydrate” throughout. Do not accept carbohydrates are broken down/hydrolyzed.
Whilst many could quote from 7b, that starch undergoes hydrolysis, very few linked this to a biochemical mechanism. Other factors, relating to the reduction of intermolecular forces between the polymer chains were also rarely encountered.
