closed systems

A closed system is a type of system where matter cannot enter or exit; it is self-contained. In such systems, only energy can be exchanged with the surroundings, but not matter. For example, a sealed container holding gas is a closed system—no gas leaks in or out, though heat might transfer in or out. Closed systems are useful in scientific and engineering contexts to analyze processes where matter remains constant, and only energy transfer occurs, simplifying the study of how systems behave over time.