Hello! This question is not about a particular homework exercise, or any exercise, but rather an astonishing real life fact, which I just experienced, and, as I am still on my way to becoming educated in science, I would like to ask for your help on how to explain this phenomena. I had a rather warm pure water, and I wanted to warm it up, almost to a boiling point. I put a small uncovered flat round pan (radius about 10, or less, cm; and the hight of edges is about 4 - 5 cm), filled with water of about 3 cm in hight, on the electric stove and turned on the heat. As the water was already warm, it should have come to a boiling point within 2 - 3 minutes, given the way my stove works. But in 5 minutes I didn't see any boiling, nor even any air tiny bubble, which usually form before the water reaches the boiling point; the water was flat and tranquil, with a tiny steam coming out of it. I decided to use it as it is. But! When I lifted the pan, and thus stirred the water a bit by starting to move the pan away from the stove, the water suddenly bursted out, started bubbling heavily, really heavily, spilling all over. It looked as if there was something on top of it that prevented it from showing the physical boiling while it was quietly sitting on the hot stove, even though it had reached the boiling temperature. What could it be? What type of physical / chemical phenomena is it? Thank you very much!