The snapshot of the system (the global state) taken with a state camera does not change with time when a system is at steady state. The global state remaining frozen, the total  mass, energy, and entropy of the system remain constant and their time derivatives become zero. As a result, the differential balance equations simplifies into algebraic equations.

The bulk of open system problems involving devices such as nozzles, turbines, pumps, compressors, diffusers, condensers, evaporators, etc., belong to this category. A number of animations in VT, Chapter-4, illustrate open steady systems.

If the global image (state) changes with time, the system is called unsteady. Furthermore, if the instantaneous rate of change of any property (rate of change of temperature, for instance) is of interest, the problem is called a transient unsteady problem.

The state daemons can be used to evaluate neighboring states from which time rate of change can be calculated in the I/O panel. Currently, there is no dedicated daemon for transient analysis (hence no icon on the left column) since transient problems are rare in thermodynamics.

Most unsteady problems involve a process - transition of the system from a begin-state (b-state) to a finish-state (f-state). The balance equations (see below), therefore, can be integrated over the process, resulting in algebraic equations.