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CAIE IGCSE Physics Thermal Expansion Overview

Practise comparing expansion in solids, liquids and gases and apply particle explanations to thermometers, thermostats, bridges, rails and expansion gaps.

Syllabus
2026–2028
Course
Physics 0625

Exam points

  • compare expansion by identifying gases as greatest and solids as least for equal heating
  • explain expansion through increased particle motion, separation and intermolecular forces
  • apply expansion to thermometer design, bimetallic thermostats and structural gaps

Covered syllabus points

2.2.1.1—Qualitatively the thermal expansion of2.2.1.2—Some of the everyday applications and2.2.1.3—Explain, using particle motion and

2.2.1 Thermal expansion of solids, liquids and gases question 1

[Maximum number: 5]

Question (a)

(a)

A glass tube passes through a stopper and into a glass flask. Fig. 4.1 shows that the flask is completely full of a liquid and that there is also some liquid in the tube.

Fig. 4.1

Fig. 4.1

The flask is immersed in a large beaker of very hot water. At first, the level of the liquid in the tube falls, but after a short time it rises.

[ 5 ]

Question (i)

(i)

Explain why, at first, the level of the liquid in the tube falls.

[ 3 ]

Question (ii)

(ii)

Explain why the liquid level in the tube stops falling and starts to rise.

[ 2 ]

2.2.1 Thermal expansion of solids, liquids and gases question 2

[Maximum number: 10]

Fig. 5.1 shows the structure of a liquid-in-glass thermometer.

Fig. 5.1

Fig. 5.1

The bulb of the thermometer is placed into a beaker of warm water. As the liquid expands, it moves along the tube.

Question (a)

(a)

Explain, in terms of molecules, why a liquid expands when heated.

[ 2 ]

Question (b)

(b)

Explain, in terms of molecules, why a liquid expands more than a solid when heated.

[ 2 ]

Question (c)

(c)

A second thermometer has a larger bulb that contains more of the same liquid than the thermometer shown in Fig. 5.1. It has a different scale. In every other way, it is identical.

[ 3 ]

Question (i)

(i)

Explain how the sensitivity of the second thermometer compares with the sensitivity of the thermometer in Fig. 5.1.

[ 2 ]

Question (ii)

(ii)

Explain how the range of the second thermometer compares with the range of the thermometer in Fig. 5.1.

[ 1 ]

Question (d)

(d)

State one everyday problem that is a result of thermal expansion.

[ 1 ]

Question (e)

(e)

Suggest and explain one way of solving this problem.
[Total: 10]

[ 2 ]
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