Practice question

**Energy transfer** first law ΔU = Q - W, W includes P-V work, shaft work, electrical work, Q includes conduction Fourier law, convection, radiation Stefan-Boltzmann, distinction important because work is controllable, heat spontaneous from hot to cold, entropy associated with heat not work, explaining why heat engine efficiency <100%. P₁ V₁^γ = P₂ V₂^γ . 9 × 18¹.4 = 3 × V₂¹.4 . V₂¹.4 = (9)/(3) × 18¹.4 = 3 × 18¹.4 . 18¹.4 ≈ 39.4 , V₂¹.4 = 3 × 39.4 ≈ 118.2 . V₂ = (118.2)¹/1.4 ≈ 31.8 L . Using first law ΔU = Q - W, W = ∫ P dV,