Thermodynamics Problem Solving

This final lesson brings together all the concepts from the course — specific heat capacity, specific latent heat, the ideal gas equation, kinetic theory, molecular kinetic energy, and the first law of thermodynamics — into multi-step problems that mirror the style and difficulty of Edexcel A-Level exam questions. Work through each example carefully, noting the problem-solving strategies.

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Strategy for Multi-Step Thermal Physics Problems

1. Identify what is being asked and which concepts are involved.
2. List the known quantities with their SI units.
3. Choose the correct equation(s): Q = mcΔθ, Q = mL, pV = nRT, pV = NkT, pV = ⅓Nm⟨c²⟩, ½m⟨c²⟩ = 3/2 kT, ΔU = Q + W, W = pΔV.
4. Convert all units to SI before substituting.
5. Check the sign conventions for the first law (Edexcel: W = work done on gas).
6. Evaluate your answer — does it make physical sense?

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Worked Example 1: Combined SHC and Latent Heat

How much energy is needed to convert 0.40 kg of ice at −15 °C into steam at 100 °C?