IB Physics: Thermal Physics Revision

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Why does a gas's pressure rise when heated at constant volume?

Thermal Physics is a core part of IB Physics. Revise the key concepts and common mistakes below, then lock them in with the free games.

Key concepts

Ideal gasPoint particles, no IMF

pV = nRTp Pa, V m³, T K, R = 8.31

k_BBoltzmann constant, 1.38×10⁻²³ J/K

RMS speed√⟨v²⟩

Mean KE(3/2)k_B T per molecule

Maxwell-BoltzmannSpeed distribution

PhaseSolid, liquid, gas

Specific latent heat LEnergy per kg to change phase

L_fusionSolid → liquid (ice: 334 kJ/kg)

L_vaporisationLiquid → gas (water: 2260 kJ/kg)

PlateauFlat T on cooling/heating curve

SublimationSolid → gas directly

TemperatureMean KE of particles

Kelvin KAbsolute scale; 0 K = -273.15°C

Learn Thermal Physics step by step

Free interactive mini-lessons: short screens, worked examples and quick checks. Pick your exam board:

Common mistakes to avoid

Questions where students often pick the tempting wrong answer — make sure you know the right one:

Why does a gas's pressure rise when heated at constant volume?✗ The particles themselves expand. ✓ Particles move faster and hit the walls harder and more often.

What happens to temperature while a pure solid melts?✗ It keeps rising steadily. ✓ It stays constant — energy breaks bonds, not raises temperature.

Practise Thermal Physics — free games

Test yourself with these quick revision games for this topic:

▶ Two Truths, One Lie ▶ Reveal Race ▶ Connections Grid ▶ Falling Words ▶ Word Web

See all 22 games in the Revision Arcade →

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