Thread: Weird phenomena while boiling water....

Earlier I was boiling water on the stove. For whatever reason, I added an ample amount of cold water to the kettle as it was boiling. What surprised me was that the kettle seemed to "explode" from the inside at random times.

Why does it do this?

My guess is that the extreme temperature difference and the cold water not being distributed evenly....but I can't seem to explain why the "explosion" was quite forceful.

Go ahead. Try it yourself:
1)Get water to boil in a kettle.
2)As the water is boiling, add a cup or more of cold water.
3)IMMEDIATELY cover the kettle and stand back! The water did splash at the top....

I tried searching for this phenomena but I failed. If you can tell me what this is, that'll be great.

I understand double posts are not allowed but I think given the circumstances, its allowed in this case.

So I tried the experiment again this morning. My results weren't as profound as last night. I decided to use a different pot this time to see if I'd get the same results. I got the water to boil and left it for a bit. After that, I poured a small amount of cold water. Results: Nothing happened.

Puzzled, I decided to use the teapot/kettle I used last night. I got the same results but the "explosions" were not as forceful as they had been the night before and they were less frequent (last nights "explosions" happened a lot).

It should be noted that:
1)The "explosions" came ONLY from the kettle. I got no results with the other pot.

2)The surface area of the bottom of the kettle was exactly the same as the other pot. They are both made of stainless steel. However, the bottom of the kettle has sediments (which gives it a rusted look) from the water and the other pot was clean.

3)I used normal cold water from the faucet and cold water I had from the fridge.
Results: The colder water yielded more "explosions".

4)Yesterday's weather was different than today's. It is possible that atmospheric pressure plays a big role in this experiment (no matter how small the difference).

I'm definitely looking for someone else to tell me what they have found. I'm sure that most of you won't get the same results (if any) as I did. But, its a shot.

Possibly there was poor convection in the kettle, so that although the water was, on average, hot enough to boil, most of the heat could have been trapped in small regions which had been superheated (close to the heating elemtent in this case). With the addition of the cold water, the water already in the kettle is mixed, rapidly heating all of the water to the boiling point, and supplying the latent heat, so that the water begins to evaporate.

This is a fairly well known phenomena in narrow vessels, e.g. mugs of water in a microwave often boil suddenly and rapidly because of superheated zones in the water where convection does not occur. What caused it to happen in your kettle, I couldn't tell you, but superheating and lack of convecting currents seems to be the only explanation to me.

Originally Posted by drowsy turtle

Possibly there was poor convection in the kettle, so that although the water was, on average, hot enough to boil, most of the heat could have been trapped in small regions which had been superheated (close to the heating elemtent in this case).

Makes sense. Poor convection and superheating. Maybe the cold water "held down" some hot water and that portion of hot water got superheated. That also explains why this did not happen on the other pot. Thanks man....