O-LevelPhysicsThermal Physics5054/21 · May/June 2023 · Q57 Marks

Fig. 5.1 shows the particles (molecules) in a sample of liquid water. [Figure 5.1]

(a)Explain, using ideas about particles, why liquids expand more than solids for the same temperature rise.[2]
(b)(i)State the boiling point of water on the Kelvin scale of temperature.[1]
(b)(ii)The temperature remains constant as water turns from liquid to gas at the boiling point. Explain, in terms of particles, why energy must be provided even though the temperature stays constant.[1]
(c)An electric heater is used to heat a sample of metal, as shown in Fig. 5.2. There is no thermal energy transferred from the metal to the surroundings during the heating. [Figure 5.2] The metal has a mass of 200g and is initially at 15°C. The heater is switched on for 2.0 minutes and then switched off. The maximum temperature reached by the metal is 40°C. The power of the heater is 20 W. Calculate the specific heat capacity of the metal. Show your working.[3]

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Mark scheme

Marking points from the official mark scheme (May/June 2023). The mark or mark type is shown in brackets.

[B1] as temperature rises / heat added particles move faster / vibrate faster / move further apart
[B1] smaller force between particles (in liquid) OR regular/fixed arrangement of particles in a solid or more space between particles in a liquid / less tightly packed / particles further apart
[B1] 373 (K)
[B1] (energy needed) to separate particles / increase potential energy of particles / overcome (intermolecular) forces (of attraction)
[B1] E = Pt in any form, algebraic or numerical, seen, e.g. 2400 (J)
[B1] (shc =) E/ mT in any from
[B1] 0.48 (J/(g°C))

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