O-LevelPhysicsThermal Physics5054/21 · May/June 2022 · Q36 Marks

Define latent heat of fusion.

(a)Define latent heat of fusion.[2]
(b)(i)A sample of metal P at 100°C is heated steadily until its temperature reaches 400 °C. The melting point of the metal is 250 °C. On Fig. 3.1, sketch a graph to show how the temperature of the metal changes with time.[Figure 3.1][2]
(b)(ii)A sample of a different metal Q has a greater latent heat of fusion than the sample of P. P and Q are metals with the same melting points and the samples have the same heat capacity. The experiment is repeated with the sample of Q. This sample is supplied with the same amount of energy per second as is supplied to the sample of P. Explain how the graph of temperature against time for Q differs from the graph in (b)(i).[2]

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Mark scheme

Marking points from the official mark scheme (May/June 2022). The mark or mark type is shown in brackets.

[1] (a) amount (of heat / energy) needed to change the state from solid to liquid
[1] (a) without a change in temperature
[1] (b)(i) rising from 100 °C and flat section at 250 °C
[1] (b)(i) rising from flat section to 400 °C / longer at 250 °C
[1] (b)(ii) longer flat section or longer time at 250 °C
[1] (b)(ii) needs more energy / heat to melt

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