Originally Posted by
Brandon Chew
Generally speaking: the temperature at which boiling occurs (boiling point) depends upon pressure. At sea level (14.7 psia or 0 psig), yes water boils at 212 degrees.
Yes, I was referencing the sea level boiling point as Jack stated 212 degrees.
Water will boil at higher temperatures when under pressure (hence the use of the "pressure cooker") ...
Correct, but an open pot is not under pressure. I may have erred when I "assumed" Jack was referencing an "open pot".
When it begins boiling, liquid water will continue to boil at the same temperature (dictated by the pressure). As more heat is applied the rate of boiling increases but the temperature remains the same. The steam will be at a much higher temperature than the boiling water.
Okay, that is what I was referring to.
However there is also a special case called superheating. A liquid can be heated to a temperature significantly above it's normal boiling point if it is heated in a smooth walled container and kept very still. This prevents those little bubbles from forming in the water (called nucleation) and delays the onset of boiling. When being superheated, the water is storing energy that will be released in a steam explosion accompanied with rapid boiling if the water is disturbed.
Superheating is a concern when using microwave ovens to boil water, especially those units without turntables. Opening the door, setting the cup down on the counter, dropping a tea bag or a spoon of sugar into it ... any of these could kick off the boiling process and send scalding water flying. Many people have gotten severe burns from this.
Thank you, learned something new today. I had heard of "superheating" but never in reference to something like that.