Question 22M.2.SL.TZ1.d.ii
| Date | May 2022 | Marks available | [Maximum mark: 3] | Reference code | 22M.2.SL.TZ1.d.ii |
| Level | SL | Paper | 2 | Time zone | TZ1 |
| Command term | Determine | Question number | d.ii | 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.
The missing section of insulation is 0.56 m long and the external radius of the pipe is 0.067 m. The emissivity of the pipe surface is 0.40. Determine the energy lost every second from the pipe surface. Ignore any absorption of radiation by the pipe surface.
[3]
use of where T = 357 K ✓
use of « = 0.236 m2» ✓
P = 87 «W» ✓
Allow 85 – 89 W for MP3.
Allow ECF for MP3.
Candidates at both levels were able to recognize that this was a blackbody radiation question. One common mistake candidates made was not calculating the area of a cylinder properly. It is important to remind candidates that they are expected to know how to calculate areas and volumes for basic geometric shapes. Other common errors included the use of T in Celsius and neglecting to raise T ^4. Examiners awarded a large number of ECF marks for candidates who clearly showed work but made these fundamental errors.
