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CAIE A-Level Physics 14.1.2 Equal Temperature and Thermal Equilibrium

Practise recognising thermal equilibrium from equal temperatures and interpreting when no net thermal energy transfer occurs between regions.

Syllabus
2028–2030
Course
Physics 9702
Level
A2

Exam points

  • identify thermal equilibrium as the condition in which regions have equal temperature
  • interpret whether energy transfer has ceased between regions at thermal equilibrium

14.1.2—Regions of equal temperature are in thermal equilibrium question 1

[Maximum number: 3]

Fig. 2.1 shows a laboratory thermometer that is calibrated to measure temperature in degrees Celsius.

Fig. 2.1

Fig. 2.1

The thermometer makes use of the fact that the density of mercury varies with temperature.

The thermometer is initially at 23.0∘C23.0^{\circ} \mathrm{C}, as shown in Fig. 2.1. It is used to measure the temperature of an insulated beaker of water that is at 37.4∘C37.4^{\circ} \mathrm{C}. The bulb of the thermometer is inserted into the water, and the water is stirred until the reading on the thermometer becomes steady.

The mass of water in the beaker is 18.7 g .
The mass of mercury in the thermometer is 6.94 g .
The specific heat capacity of water is 4.18 J g−1 K−14.18 \mathrm{~J} \mathrm{~g}^{-1} \mathrm{~K}^{-1}.
The specific heat capacity of mercury is 0.140 J g−1 K−10.140 \mathrm{~J} \mathrm{~g}^{-1} \mathrm{~K}^{-1}.
The glass of the thermometer and the beaker containing the water can be considered to have negligible heat capacity.

Calculate, to three significant figures, the final steady temperature indicated by the thermometer in the water. ∘C{ }^{\circ} \mathrm{C}

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