During a boil over, what happens to the boiling water at the bottom?

• A. It boils and expands rapidly
• B. It cools instantly
• C. It stays at constant temperature
• D. It disappears from the tank

Answer: (A)

When water reaches its boiling point, adding heat turns liquid water into steam. In a boil over, the water at the bottom keeps boiling vigorously, producing a large amount of steam that expands rapidly. This rapid vapor generation pushes the liquid and foam up to the surface, causing the contents to spill over the tank. The water isn’t cooling instantly or disappearing; it’s being converted into steam, and the steam volume is far greater than the liquid, leading to the overflow. So the bottom water boils and expands rapidly.