I am a student in my third year of engineering (materials science) and I was performing a lab experiment in which I was asked to calculate the heat capacity of metals using thermodynamic relationships. The experiment was done by placing a metal sample into a foam container filled with liquid nitrogen. I had to wait until the liquid nitrogen stopped boiling (this indicated that the temperature of the metal had reached the temperature of the liquid nitrogen. The amount of liquid nitrogen evaporated was measured and used to calculate how much energy was transferred from the metal to the liquid. And from there, the heat capacity was calculated. (That was the experiment in a nutshell). So the weird thing I noticed was this: During the time I had to wait until the liquid nitrogen stopped boiling, I noticed that RIGHT BEFORE the liquid nitrogen ceased boiling it actually boiled VERY FURIOUSLY and THEN it ceased. I don't how to explain how to explain this clearly but picture this: the metal is dropped in the container; you see the liquid nitrogen boiling as usual you wait and wait all of sudden it starts to boil a LOT more furiously then, about a second later, it suddenly calms down and reaches equilibrium. What I was expecting was that it would just boil then calmly cease to boil but this clearly was NOT what I saw. My mind was blown and I STILL can't figure out what happened. Would anyone please be kind enough to explain this strange phenomenon?