What is an isolated system?

An isolated system is defined as a physical system that does not exchange either matter or energy with its surroundings. This means that the total energy and the amount of matter within the system remain constant over time, as no external influences can alter these quantities.

In the realm of thermodynamics, this concept is crucial because it establishes a boundary where no external work is done on or by the system, and no heat is exchanged. The importance of this definition lies in the fact that isolated systems are often used as idealizations in theoretical models, helping to simplify the analysis of thermodynamic processes under controlled conditions.

Considerations regarding the other options clarify the distinctions in types of systems: systems that can exchange energy but not matter are known as closed systems; those that allow interaction with their environment are referred to as open systems; and systems that permit matter transfer while restricting energy transfer represent a different category altogether. Thus, the true characterization of an isolated system is clearly captured by the definition of no exchange of matter or energy.