Because technically the steam is dissolved in the water above its saturation point, right? If the gas were (say) CO2 instead of steam, wouldn’t “supersaturated” be the correct term?
If the gas were CO2 instead of steam, CO2 would be the solute, and water the solvent. In that case the term supersaturated would make sense because the solvent contains more solute than it can handle under normal conditions. The steam is not disolved in the water. The microwaved water is unable to form steam in the first place due to a lack of available nucleation sites.
I thought superheating referred to heating water over 100º by pressurizing it
That isn’t superheating. The boiling point of a given substance naturally varies with pressure. Liquid water at 200oC while pressurized sufficiently isn’t superheated. It is just hotter than you expect it to be. That technique can be used to superheat something like water if heated over it’s atmospheric boiling temperature while pressurized and then lowering the pressure without agitating it.
If the gas were CO2 instead of steam, CO2 would be the solute, and water the solvent. In that case the term supersaturated would make sense because the solvent contains more solute than it can handle under normal conditions. The steam is not disolved in the water. The microwaved water is unable to form steam in the first place due to a lack of available nucleation sites.
That isn’t superheating. The boiling point of a given substance naturally varies with pressure. Liquid water at 200oC while pressurized sufficiently isn’t superheated. It is just hotter than you expect it to be. That technique can be used to superheat something like water if heated over it’s atmospheric boiling temperature while pressurized and then lowering the pressure without agitating it.