Isolated System

An isolated system is characterize by the fact which it has no interaction with its surroundings. The grouping of system plus surroundings, making up the universe, is an illustration of an isolated system.  

In summing up, the permissible interactions for the three classes of areas defined above might be defined as follows:

System:

Heat and/or work.

Control Volume:

Heat and/or work and/or mass.

Isolated system:

No interaction allowable.

                  Figure: Permissible Interactions for System, control volume & isolated system