Which statement accurately describes a boil over concept?

• A. Water at the bottom of the tank boils and causes rapid expansion
• B. Water at the bottom of the tank boils and causes rapid cooling
• C. Water at the top of the tank boils and causes rapid expansion
• D. No boiling occurs in a boil over

Answer: (A)

Boil-over occurs when water at the bottom of the tank is heated to boiling. The steam that forms expands rapidly, pushing the surrounding liquid upward and causing it to overflow over the sides. In tanks where oil sits on top of water, that bottom-water boiling creates enough expansion to lift the oil and push it out of the tank. This is why describing it as water at the bottom boiling and causing rapid expansion fits boil-over best. Boiling at the top wouldn’t produce the same pushing effect, and saying no boiling occurs ignores the key mechanism that drives the overflow.