[mana]

Hi all
some students were trying to measure boiling point of water by heating a half full beaker containing distilled water on a heater, near the boiling point of water (above 90 ^oC) when their thermometer contacted with the bottom of the beaker, the boiled water spilled out suddenly, all the time that they did that the water spilled out. can anyone explain why this happen?

[Hunter2]

At the bottom the temperature is more hot and the water is overheated. To ditch with something to the bottom it disturbs and the water directly vaporise and the steam pull out the liquid water.
Compare put some small boiling stones in the Beaker and it will not happen.

[Vidya]

Hunter is right. When we add pumice stone during boiling of liquids ,we create a passage for steam collected at the bottom(due to difference in temp) to move out and this helps in preventing liquid to *Ignore me, I am impatient* out.