CoachA physico-chemical system is the matter contained in a chosen region of space, the rest being its surroundings. It is a closed system if it exchanges no matter with the surroundings (it may exchange energy). A phase is a part of the system in which the intensive variables vary continuously: a gas mixture is one phase, two immiscible liquids are two phases, each solid is a phase of its own.
Chemistry · Glossary
What is System, phase?
Also known as: physico-chemical system · closed system · phase