O-LevelPhysicsThermal Physics5054/21 · Oct/Nov 2021 · Q915 Marks

Liquid-in-glass thermometers use the expansion of a liquid to indicate the temperature.

(a)(i)Fig. 9.1 shows the molecular structure of a solid and a gas. [Figure 9.1] In the middle box of Fig. 9.1, sketch a diagram to show the molecular structure of a liquid.[2]
(a)(ii)Explain why it is easier to compress a gas than to compress a solid.[2]
(a)(iii)The temperature of a liquid-in-glass thermometer increases. State two ways in which the molecules of the liquid in the thermometer are affected. 1. 2.[2]
(b)(i)Fig. 9.2 shows the liquid-in-glass thermometer. [Figure 9.2] There is no scale on the thermometer. State what is meant by the ice point and the steam point. ice point steam point[2]
(b)(ii)Describe how the ice point and the steam point are used on the thermometer.[2]
(c)(i)Explain how the range of a liquid-in-glass thermometer is affected by: increasing the mass of liquid in the bulb[2]
(c)(ii)increasing the diameter of the narrow tube.[3]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2021). The mark or mark type is shown in brackets.

[B1] molecules with similar / slightly smaller packing density and most molecules touching
[B1] random arrangement
[B1] molecules (of gas) further apart
[B1] (repulsive) forces between molecules (much) smaller
[B2] any two of: move faster/greater kinetic energy; move further apart; forces (slightly) smaller
[B1] (ice point) where ice and water are in equilibrium or melting point / temperature of ice
[B1] (steam point) where water and steam (water vapour) are in equilibrium or boiling point / temperature of water
[B1] 0 (°C) marked at level of thread in ice-water mixture or at ice point or 100 (°C) marked at level of thread in water-steam mixture or above boiling water or at steam point
[B1] interval between marks divided into 100 divisions
[B1] it/range decreases
[B1] (a greater mass) expands more / further along the (capillary) tube (for same temperature increase) or range / it is inversely proportional to mass
[B1] it/range increases
[B1] range / it is proportional to square of diameter or more expansion / greater volume increase needed (for thread to reach end of the tube)
[B1] greater temperature increase needed (for greater volume increase)

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