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the total mass will remain the same even if there are physical or chemical changes closed system prevents anything already in the system from leaving and does not allow anything else to get into the system. For example, the Alka tablets in the glass of water in the form an open system by escaping into the air while The balloon and conical flask form a closed because the gas produced in the flask is trapped by the balloon and cannot leave the system.

Conservation of mass in a closed system the total mass will remain the same even if there are physical or chemical changes.