System:
In thermodynamics, a substance or group of substances in which we have special interest is
called a system. It is that part of the universe which is set apart for our special consideration. It may
be a reaction vessel, a distillation column, or a heat engine.
Process:
The changes taking place within the system is referred to as a process. Thus, hydrocarbon
fuel and oxygen in a combustion chamber constitute the system and the combustion of fuel to form water and carbon dioxide constitutes a process.
Surrounding:
The part of the universe outside the system and separated from the system by
boundaries is called surroundings. The boundaries may be either physical or imaginary; they may be
rigid or movable. For practical reasons, the surroundings are usually restricted to that portion of the universe which is in the immediate vicinity of the system and are affected by changes occurring in the
