Practice question

**Modes of energy transfer** work is force times displacement, e.g., gas expansion W = P ΔV, heat is due to temperature gradient, internal energy change same for different combinations of Q and W, e.g., same ΔU can be achieved by adding heat at constant volume or doing work adiabatically, illustrating equivalence but distinction in mechanism. The Second Law limits efficiency and directionality (e.g., no 100% heat-to-work conversion, Kelvin-Planck). Option B is incorrect; it contradicts the law, which requires heat rejection to a cold reservoir. Using first law ΔU = Q - W, W = ∫ P dV, isobaric W = P ΔV, isothermal W =