Now that we know the different types of systems (batch, semi-batch, continuous) and how they might be operated (steady, transient), it is useful to have one further layer of classification:
A closed system is one where no mass moves across the boundaries. In terms of a flowchart, this means that there are no streams entering or leaving the closed system (in practice, this means that stuff goes in at the beginning and comes out only at the end).
An open system is one where mass does move across the boundaries. In practice, this means that stuff goes in or out at some point during the process (not simply at the beginning and/or ending).
Open/closed tells us whether the system is isolated from its surroundings in terms of mass flow across the boundaries. Our last classifications have to do with whether a system is isolated from its surroundings in terms of heat flow and whether it changes temperature:
An adiabatic system is one where no thermal energy (heat) moves across the boundaries (in practice, this is accomplished through the use of insulation, so this is often also called an "insulated" system).
An isothermal system stays at a single constant temperature with respect to time.
Define open system, closed system, adiabatic, isothermal