Chemistry · Ch 7 — Thermodynamics
Types of Systems
Types of Systems
Thermodynamic systems are sorted into three types purely by what their boundary permits to cross it -- matter, energy, both, or neither.
Isolated system. A system whose boundary is both sealed and insulated, so that neither matter nor energy can cross it in either direction. Hot water sealed inside a thermos flask is the textbook example: as long as the flask holds, no water vapour (matter) escapes and no heat (energy) enters or leaves -- both stay trapped, keeping the system's total energy and composition fixed.
Closed system. A system whose boundary is sealed but not insulated -- it can exchange energy with its surroundings, but not matter. Hot water in a closed (but not vacuum-jacketed) beaker is a closed system: heat can conduct out through the glass to the surroundings, but no water vapour can physically escape. A gas trapped in a cylinder fitted with a piston is the other standard closed-system example -- the piston can move (letting energy in or out as work) but no gas molecules can leave the cylinder. …
What this figure shows. Three small vessels drawn side by side, each holding a pink liquid. 'Open' is a plain test tube, unstoppered, liquid level visible at the top -- free exchange with the room. 'Closed' is an identical test tube but capped with a green stopper -- sealed against matter loss, but an ordinary glass wall still conducts heat. 'Isolated' is drawn as a double-walled, jacketed flask (a thermos-like vessel) with its own cap -- both sealed AN …