In a closed system, mass cannot be added or removed; hence this principle applies stating that mass remains constant irrespective of its transformations inside the system.
First Law of Thermodynamics: This law states that energy cannot be created or destroyed but only transferred or transformed, which perfectly describes what happens within a closed system.
Adiabatic Process: An adiabatic process occurs without transfer of heat or mass between a thermodynamic system and its surroundings - similar to what happens in some types of closed systems.