Overcharging a battery commonly causes the water to evaporate.

• A. Increase
• B. Decrease
• C. Evaporate
• D. Remain unchanged

Answer: (C)

Overcharging pushes more current into the battery than it can safely handle, causing the electrolyte to heat up and water to be lost. The excess voltage drives water in the electrolyte to split into hydrogen and oxygen, which leaves as gases, and the hot liquid can also turn to vapor and escape. This combination means the water content drops because it turns into vapor and escapes from the battery. So describing the effect as water evaporating fits the observed loss of water due to both heat and gas evolution. The water isn’t increasing, and it isn’t simply staying the same; it’s being converted to vapor and leaving the cell.