Which describes an open system?

Which describes an open system?

• A. Transfer of Both Mass and Energy With Surroundings
• B. No Mass Transfer Across Boundaries
• C. No Energy Exchange With Surroundings
• D. Energy Transfer Only, With No Mass Exchange

Answer: (A)

Open system behavior is defined by matter crossing the system boundary. When mass flows in or out, it carries energy with it, so there is exchange of both mass and energy with the surroundings. This is exactly what the description of transferring both mass and energy with the surroundings conveys, making it the correct way to describe an open system. If no mass crosses the boundary, you’re dealing with a closed system, even if energy can be exchanged. If there’s no energy exchange, the system is isolated. If energy can cross but mass cannot, that situation is effectively a closed system with energy transfer, not an open one.

Open system behavior is defined by matter crossing the system boundary. When mass flows in or out, it carries energy with it, so there is exchange of both mass and energy with the surroundings. This is exactly what the description of transferring both mass and energy with the surroundings conveys, making it the correct way to describe an open system.

If no mass crosses the boundary, you’re dealing with a closed system, even if energy can be exchanged. If there’s no energy exchange, the system is isolated. If energy can cross but mass cannot, that situation is effectively a closed system with energy transfer, not an open one.