Superheating is a phenomenon that occurs when a liquid is heated above its boiling point such that the liquid does not boil. It is usually observed in pure homogenous liquids that do not have a nucleation centre to initiate the boiling once the temperature hits the boiling point.
Frequently Asked Questions
Why liquids need a nucleation centre to initiate boiling?
Nucleation centres are responsible for creating the initial air pockets inside the container in which the liquid is boiled. So when the liquid reaches its boiling point, the already existing air pocket at the nucleation centre aids the other molecules to aggregate into a bigger bubble and eventually escape the liquid as vapour. Impurities, rough surfaces of the container and other particulates serve as nucleation centres.
The typical example is the domestic water. It has many impurities that would serve as nucleation sites. This is the reason why you don't find your domestic water superheating in the stove or microwave oven. Distilled water, however, lacks impurities and thus lack nucleation centres. If boiled in a smooth container that doesn't have any air pockets in it, the water can be superheated.
Could superheated water explode?
Yes! Superheated water is simply a liquid that is above its boiling point with enough kinetic energy in its molecules that are one nucleation away from boiling instantaneously. So if you introduce a speck of dust enough to create an air pocket in it, the water would explosively boil.