Closed System Characteristics Explained

A closed system is a key concept in thermodynamics. Its behavior is defined by how its boundaries interact with the surroundings.

Defining a Closed System

The defining features of a closed system are:

• Energy can be exchanged across its boundaries with the surroundings (as heat or work).
• Mass cannot be exchanged across its boundaries; it remains constant within the system.

Analyzing the Options

Let's examine how each option fits the definition of a closed system:

• Options 1 & 2: State only one direction of energy transfer (in or out). This is incomplete as energy can flow both ways.
• Option 3: Accurately describes that energy transfers can occur between the system and the surroundings in both directions (system to surrounding and vice-versa). This aligns with the definition, as mass transfer is not mentioned or implied.
• Option 4: Describes both energy and mass crossing boundaries. This is the definition of an open system, not a closed one.

Correct Description

Option 3 correctly identifies the nature of energy exchange in a closed system, distinguishing it from mass transfer.