Practice question

**Zeroth law of thermodynamics** if two systems A and B each in thermal equilibrium with third C, then A and B in equilibrium with each other, defines temperature as property that is same for systems in thermal equilibrium, basis for thermometer, temperature scale, thermal equilibrium means no net heat flow, same temperature. First Law: Δ Q = Δ U + Δ W . Δ Q = 920 , Δ W = 280 (work by system). 920 = Δ U + 280 ⇒ Δ U = 920 - 280 = 640 J . Using first law ΔU = Q - W, W = ∫ P dV,