CFE Physical Science Honors 2025 – 400 Free Practice Questions to Pass the Exam

A closed system is characterized by the inability to allow matter to enter or leave, while still permitting the exchange of energy with the surroundings. This definition is crucial in various scientific contexts, particularly in thermodynamics, where closed systems help researchers understand the behavior of energy transfers without the complexity introduced by matter exchange.

For example, in a closed container of gas, the gas molecules can move and interact with each other, demonstrating energy transfer through temperature changes or work done on the system, but no gas can escape or enter the container. This concept helps in analyzing processes such as heat engines where energy is converted from one form to another while ensuring that the mass remains constant.

The other scenarios provided do not accurately capture the principle of a closed system. Systems that could allow matter to flow freely or those that permit both matter and energy exchange do not meet the definition of a closed system, as they involve interactions that allow for changes in mass within the system.