Explanation: The level of the liquid in a sealed jar decreases slightly due to the evaporation of some of the liquid molecules into the air space above the liquid. However, once the concentration of the liquid molecules in the air space reaches a certain level, the rate of evaporation will slow down. This is because the concentration of the liquid molecules in the air space will eventually reach a point where the rate of evaporation is balanced by the rate of condensation.
At this point, the liquid molecules in the air space will be colliding with the surface of the liquid at the same rate that liquid molecules are evaporating from the surface of the liquid. As a result, the level of the liquid will cease to change, and the liquid will remain at a stable level within the jar.