Why does adding salt to boiling water cause it to flare up suddenly? I was expecting that the water would become less "boily" since the ions in $\ce{NaCl}$ would require energy to disassociate. Instead it turned whitish and the water level suddenly rose and then subsided. I think the white color can be attributed to the fact that table salt is white but why did the water suddenly flare up ?
The salt does not instantly dissolve so the surface of the crystals suddenly provides a lot of nucleation sites for the water to form vapour - hence the surge as it boils from these surfaces. The white is due to turbulence from the boiling just like waterfalls look white.