What is the immediate effect described in a boil over?

• A. Rapid expansion due to boiling water
• B. Rapid cooling of the water
• C. Steady pressure with no change
• D. Condensation at the surface

Answer: (A)

When water reaches a boil, energy drives rapid conversion of liquid into steam. That steam takes up much more space than the liquid, so the volume expands quickly. In a boil over, that sudden expansion, driven by dense vapor forming inside the liquid, pushes liquid up and over the container’s rim. So the immediate effect is rapid expansion due to boiling water turning into steam, which causes the overflow. The other options don’t fit because boiling is not about cooling, it’s not a situation of steady, unchanged pressure, and condensation at the surface would actually reduce volume rather than drive overflow.