In a closed system, what happens to materials during a reversible reaction?

During a reversible reaction in a closed system, the total amount of reactants and products remains constant over time, although their concentrations may change as the reaction reaches equilibrium. In this type of reaction, the forward and reverse processes occur simultaneously, allowing the system to shift between reactants and products without any loss of material to the surroundings. This principle is a fundamental concept in chemical equilibrium, where the rate of the forward reaction equals the rate of the reverse reaction. As a result, the overall quantity of substances involved in the reaction remains the same, consistent with the law of conservation of mass.