MCQ Detailed View

In thermodynamics, systems are classified based on their ability to exchange matter and energy with their surroundings. An open system can exchange both matter and energy. For example, a boiling pot without a lid allows steam to escape, so both energy and matter are transferred to the environment.

A closed system, on the other hand, can exchange energy only, but not matter. Heat can flow into or out of the system, but the contents remain fixed. A good example is a sealed container placed on a heat source. Energy in the form of heat is transferred across the walls of the container, but the mass inside stays constant.

An isolated system exchanges neither matter nor energy with its surroundings. Perfectly isolated systems are ideal and rare in reality. A thermos bottle with perfect insulation is a practical approximation of an isolated system, as it minimizes heat exchange and prevents matter transfer.

Understanding these distinctions is crucial in physical chemistry, especially when studying chemical reactions, thermodynamic processes, and energy balances. The behavior of a system depends on whether it allows energy, matter, or both to pass through its boundaries.

In the given question, the system that exchanges only energy and does not allow matter transfer is the closed system. This property makes it distinct from open and isolated systems. Closed systems are widely used in laboratory and industrial processes to control reactions, conserve mass, and study energy changes without the loss or gain of substances.

This knowledge is essential for students to understand energy flow, reaction dynamics, and thermodynamic laws in Physical Chemistry.