In an experiment, a student heats a solid substance until it completely melts into a liquid, and then allows it to cool. The temperature of the cooling substance is recorded every minute. The table below shows the results.
| 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 | 85 | 74 | 63 | 63 | 63 | 55 | 48 | 42 | 38 | 35 | 33 |
What is the melting point of this 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.