Thermal Physics is a core part of A-Level Physics. Revise the key concepts and common mistakes below, then lock them in with the free games.
Key concepts
Kinetic theoryModel treating gas as fast-moving particles.
Mean square speedAverage of v² across all particles.
Boltzmann constantk = 1.38 × 10⁻²³ J/K = R / N_A.
Mean KE½ m c² = 3/2 kT per molecule.
Internal energySum of KE + PE of all particles.
Monatomic gasU = 3/2 N k T (only translational KE).
HeatEnergy transferred due to temperature difference.
Specific heat capacityEnergy per kg per K: c = Q / (mΔT).
Q = m c ΔTHeat to change temperature of mass m.
Latent heatEnergy for phase change at fixed T.
L_fSpecific latent heat of fusion (solid↔liquid).
L_vSpecific latent heat of vaporisation (liquid↔gas).
Ideal gasPoint particles with elastic collisions only.
PressureForce per unit area: p = F/A, in pascals.
Common mistakes to avoid
Questions where students often pick the tempting wrong answer — make sure you know the right one:
Is the internal energy of a system the same as the heat it contains?✗ Yes — internal energy is just the stored heat in the object. ✓ No — a system doesn't 'contain heat'; internal energy is the total kinetic and potential energy of its particles, changed by heating or doing work.
If a car doubles its speed, what happens to its kinetic energy?✗ Kinetic energy doubles because energy is proportional to speed. ✓ It quadruples (because KE = 1/2 mv^2 — kinetic energy is proportional to v^2).
When energy is 'lost' as heat due to friction, what has really happened?✗ Energy has been used up and no longer exists. ✓ Energy has been transferred to the thermal store of the surroundings — it's not destroyed, just dissipated.
What does specific latent heat measure?✗ The energy required to raise the temperature of 1 kg by 1 degree. ✓ The energy required to change the state of 1 kg of a substance without changing its temperature.
Why does a metal spoon in hot water heat up faster than a wooden one?✗ Metal heats up faster because it has a lower specific heat capacity, requiring less energy per degree. ✓ Metals have higher thermal conductivity, so heat is transferred more rapidly through them.
Practise Thermal Physics — free games
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