DP Physics (first assessment 2025)
Question 20N.2.SL.TZ0.3b
| Date | November 2020 | Marks available | [Maximum mark: 3] | Reference code | 20N.2.SL.TZ0.3b |
| Level | SL | Paper | 2 | Time zone | TZ0 |
| Command term | Explain | Question number | b | Adapted from | N/A |
b.
[Maximum mark: 3]
20N.2.SL.TZ0.3b
(b)
The sample begins to freeze during the thermal energy transfer. Explain, in terms of the molecular model of matter, why the temperature of the sample remains constant during freezing.
[3]
Markscheme
«intermolecular» bonds are formed during freezing ✓
bond-forming process releases energy
OR
«intermolecular» PE decreases «and the difference is transferred as heat» ✓
«average random» KE of the molecules does not decrease/change ✓
temperature is related to «average» KE of the molecules «hence unchanged» ✓
To award MP3 or MP4 molecules/particles/atoms must be mentioned.
