Example: Boundary Work during an Isothermal Process A piston-cylinder device initially contains 0.4 m³ of air at 100 kPa and 80°C. The air is now compressed to 0.1 m³ in such a way that the temperature inside the cylinder remains constant. Determine the work done during this process. (Answer: -55.45 kJ) AIR V₁ = 0.4 m³ P₁ = 100 kPa To 80°C=const. PA To=80°C = const. 0.1 0.4 V, m³ 18