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IB Physics HL B.1.5 Temperature and Kinetic Energy Question Bank

Practise HL temperature and kinetic-energy calculations for gases, astrophysics, particle speeds and early-universe energy scales.

Syllabus
First assessment 2025
Course
Physics HL
Level
HL

Exam points

  • Apply 3/2 kT to estimate molecular speeds, mean kinetic energy and temperatures in gases and astrophysical systems.
  • Use particle mass and temperature to compare speeds, then calculate kinetic-energy or pair-production thresholds.
  • Explain heating, compression and high-energy early-universe conditions through molecular motion and energy scales.

B.1.5—Kelvin temperature and kinetic energy question 1

[Maximum number: 1]

Ceres is a dwarf planet in the asteroid belt. The following data are available.

 Mean distance of Ceres from the Sun =4.4×1011 m Mean power output of the Sun =3.8×1026 W\begin{array}{ll} \text { Mean distance of Ceres from the Sun } & =4.4 \times 10^{11} \mathrm{~m} \\ \text { Mean power output of the Sun } & =3.8 \times 10^{26} \mathrm{~W} \end{array}

At low temperatures such as the mean temperature of Ceres, water undergoes a phase change directly from solid to gas.

The maximum surface temperature of Ceres is −38∘C-38^{\circ} \mathrm{C}. Observations show that significant quantities of water vapour are released from the surface of Ceres every second when the temperature is at this maximum. Calculate the mean kinetic energy of a molecule of water vapour at this temperature.

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