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Slovak Physics Olympiad Cat A study materials
Slovak Physics Olympiad Cat A study resources

Slovak Physics Olympiad Cat A: Molecular Physics and Thermodynamics

Slovak Physics Olympiad Cat A · Work through your exam, one topic at a time.

All guide sections

Molecular Physics and Thermodynamics

Core concepts

You must know the ideal-gas law in all forms (pV = nRT = NkT), the kinetic interpretation of temperature (⟨E_k⟩ = (3/2)kT per molecule), and the equipartition of energy over degrees of freedom. First law: ΔU = Q − W (or Q = ΔU + W depending on sign convention - state yours explicitly). Know isothermal, isobaric, isochoric and adiabatic processes, and the adiabatic relation pV^γ = const. Heat capacities: C_p − C_V = R for ideal gases; γ = C_p/C_V. Phase changes involve latent heat with no temperature change. Second law: entropy, reversibility, Carnot efficiency η = 1 − T_c/T_h.

Traps

  • Sign conventions for work (work done by vs on the gas).
  • Using C_p where C_V is required (isochoric heating).
  • Forgetting that temperature is constant during a phase change.
  • Mixing kelvin and celsius in efficiency formulas.
  • Assuming adiabatic means isothermal.

Worked example

One mole of monatomic ideal gas expands isothermally at T from V to 2V. W = nRT ln(2V/V) = RT ln 2. Since ΔU = 0 for an ideal gas at constant T, Q = W = RT ln 2. Rule of thumb: for an ideal gas, ΔU depends only on ΔT - a quick sanity check on any process.