Closed system
= Closed system
A <closed system> exchanges no matter with its surroundings, but can exchange <energy> through <heat> or <work>. A sealed cylinder with a moving piston is a typical idealized example. “Closed” fixes the material inventory, rather than the <volume (thermodynamics)> or the <internal energy>. An insulated cylinder can receive compression <work>; a rigid sealed vessel can receive <heat>. Neither is necessarily an <isolated system>.