Question 19M.3.hl.TZ1.8d
| Date | May 2019 | Marks available | [Maximum mark: 2] | Reference code | 19M.3.hl.TZ1.8d |
| Level | hl | 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”.
Responses to explain how including starch in plastics makes them biodegradable were sometimes lacking in detail. Some candidates simply said that “starch is soluble in water”. Some said that “starch can be broken down/hydrolyzed” but omitted the key words “by bacteria or microorganisms”.
