Which type of system best demonstrates the Law of Conservation of Mass?

• A. Closed system
• B. Isolated system
• C. Open system
• D. Adiabatic system

Answer: (A)

Mass cannot be created or destroyed in a closed environment. In a closed system, no matter can enter or leave, so the total mass measured before and after a process stays the same. This makes a closed system the clearest way to demonstrate the Law of Conservation of Mass in practice. If the system were open, matter could escape or be added during the process, so the observed mass could change even though the actual reactions conserve mass overall. An isolated system also conserves mass, but it’s an idealized condition that’s harder to achieve in real experiments. An adiabatic system relates to no heat transfer, not mass transfer, so it doesn’t directly show mass conservation.