In a science laboratory experiment, a student heats a sample of a liquid substance in a test tube and then allows it to cool. The temperature of the substance is measured and recorded every minute as it cools and solidifies. The results are shown in the table below:
| Time (minutes) | 0.0 | 1.0 | 2.0 | 3.0 | 4.0 | 5.0 | 6.0 | 7.0 | 8.0 | 9.0 | 10.0 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Temperature (∘C^\circ\text{C}∘C) | 68 | 57 | 49 | 44 | 44 | 44 | 38 | 33 | 29 | 26 | 24 |
What is the melting point of the substance?
528 exam-style questions on CIE IGCSE Physics 2.2 Thermal properties and temperature, covering 2.2.1 Thermal expansion of solids, liquids and gases, 2.2.2a Internal energy and temperature, 2.2.2b Specific heat capacity, 2.2.3a Melting, boiling, condensation and solidification, 2.2.3b Evaporation, and 2.2.3c Cooling by evaporation. Each one has a worked solution and a mark scheme showing where the marks go.