Final answer:
Water does not stop moving when equilibrium is reached in a system. The movement of water molecules may not be visible, but they are still in constant motion.
Step-by-step explanation:
In a system where water is in equilibrium, it means that there is no net movement of water molecules between different regions. However, individual water molecules are still constantly in motion due to their thermal energy. For example, in a scenario where water is held in a U-shaped tube with a semipermeable membrane, water molecules will continue to move through the membrane from a region of higher water potential to a region of lower water potential until equilibrium is reached.
At equilibrium, there will be an equal concentration of water molecules on both sides of the membrane, but the individual water molecules will still be in motion. In summary, while there may not be a visible movement of water when equilibrium is reached, the individual water molecules are still in constant motion due to their kinetic energy.