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 |
A sample of vegetable oil, initially in the liquid state, is placed in a freezer that transfers thermal energy from the sample at a constant rate. The graph shows how temperature of the sample varies with time .
The following data are available.
Mass of the sample
Specific latent heat of fusion of the oil
Rate of thermal energy transfer
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]
«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.
