Question 22M.2.SL.TZ1.2d.iii
| Date | May 2022 | Marks available | [Maximum mark: 2] | Reference code | 22M.2.SL.TZ1.2d.iii |
| Level | SL | Paper | 2 | Time zone | TZ1 |
| Command term | Describe | Question number | d.iii | Adapted from | N/A |
Cold milk enters a small sterilizing unit and flows over an electrical heating element.
The temperature of the milk is raised from 11 °C to 84 °C. A mass of 55 g of milk enters the sterilizing unit every second.
Specific heat capacity of milk = 3.9 kJ kg−1 K−1
The milk flows out through an insulated metal pipe. The pipe is at a temperature of 84 °C. A small section of the insulation has been removed from around the pipe.
Describe one other method by which significant amounts of energy can be transferred from the pipe to the surroundings.
[2]
convection «is likely to be a significant loss» ✓
«due to reduction in density of air near pipe surface» hot air rises «and is replaced by cooler air from elsewhere»
OR
«due to» conduction «of heat or thermal energy» from pipe to air ✓
A few candidates recognized that convection was the third source of heat loss, although few managed to describe the mechanism of convection properly for MP2. Some candidates did not read the question carefully and instead wrote about methods to increase the rate of heat loss (such as removing more insulation or decreasing the temperature of the environment).
