If a closed system has adiabatic boundaries, then at least one boundary must be — Thermodynamics and Thermochemistry Chemistry Question

💡 Solution & Explanation

For a closed system with adiabatic boundaries, dq = 0. According to the first law, dU = dq + dw = dw. If all boundaries were fixed, dw = 0, which would mean dU = 0 always. To allow changes in state (dU != 0) via work, at least one boundary must be movable.