Naked Science Forum

Non Life Sciences => Chemistry => Topic started by: janfebmar on 20/04/2011 11:52:09

Title: I had an explosion with my cocoa. Why?
Post by: janfebmar on 20/04/2011 11:52:09

I had a cup of Perrier, a sparkling water which supposedly has a pH of 5.46 according to http://en.wikipedia.org/wiki/Perrier (http://en.wikipedia.org/wiki/Perrier), and put it in a microwave and heated up for about two and a half minutes. When I took it out it was bubbling as if it was boiling and it was very hot.

I then put in a dutch processed cocoa powder, which is an alkalized 100% cocoa powder http://en.wikipedia.org/wiki/Dutch_process_chocolate (http://en.wikipedia.org/wiki/Dutch_process_chocolate). The powder was floating on the water's surface, sort of clumped together as powders often do. So I stirred it with a spoon, but the moment I stirred it, everything in the cup instantly erupted in a flash and flowed out of the cup and on to the table and the floor. Almost half the water was gone and it wasn't fun cleaning it all up.

But why did it happen? I was so surprised. What's the science behind it?

Title: I had an explosion with my cocoa. Why?
Post by: RD on 20/04/2011 12:24:10

Quote from: janfebmar on 20/04/2011 11:52:09

... put it in a microwave and heated up for about two and a half minutes.

Possibly the water had become “super-heated (http://en.wikipedia.org/wiki/Superheating#Occurrence_via_microwave)”.
Stirring super-heated water alone, (no powder necessary), can cause it to “erupt”, (many gas bubbles suddenly form).

http://www.thenakedscientists.com/forum/index.php?topic=261.0

Quote from: janfebmar on 20/04/2011 11:52:09

The powder was floating on the water's surface, sort of clumped together as powders often do. So I stirred it with a spoon, but the moment I stirred it, everything in the cup instantly erupted in a flash

Adding the powder would provide many sites for nucleation (http://en.wikipedia.org/wiki/Nucleation).

See http://en.wikipedia.org/wiki/Diet_Coke_and_Mentos_eruption

Title: I had an explosion with my cocoa. Why?
Post by: JP on 20/04/2011 20:13:03

I agree completely with RD.  I have this problem all the time with making tea.  We have a hot water dispenser at work that isn't quite at boiling, so I usually fill my mug and pop it in the microwave for a minute to bring it to boiling.  Oftentimes it ends up superheated, so if I drop the tea infuser in, it boils over everywhere. 

The way around it is to either microwave it with a plastic spoon in the mug so that the bubbles have somewhere to form or to put a spoon in (carefully!) after taking it out and stir it a bit, so that it cools down enough to go below superheated.  It's easy to tell, since as you stir it, you'll see bubbles boiling up from the spoon--just stir until that stops.

Title: I had an explosion with my cocoa. Why?
Post by: Geezer on 20/04/2011 20:23:53

Sounds like another good reason to stay away from hot beverages and stick with something a lot safer, like beer.

Title: I had an explosion with my cocoa. Why?
Post by: JP on 20/04/2011 20:33:07

Quote from: Geezer on 20/04/2011 20:23:53

Sounds like another good reason to stay away from hot beverages and stick with something a lot safer, like beer.

Bottle bombs, anyone? (http://www.homebrewtalk.com/wiki/index.php/Bottle_bomb)
 [;D]

Title: I had an explosion with my cocoa. Why?
Post by: janfebmar on 20/04/2011 22:15:28

Thanks. I never could've dreamt such phenomenon exists.

Title: I had an explosion with my cocoa. Why?
Post by: SeanB on 21/04/2011 19:49:31

Plastic spoon is bad in microwave ovens, as some can absorb enough energy to melt, plus you can leach out the plasicisers from the plastic itself. I leave a stainless steel spoon, it reflects the microwaves, and it is safe in a ceramic mug as it is not near any other conductive material other than the water.

Title: I had an explosion with my cocoa. Why?
Post by: Geezer on 21/04/2011 21:31:59

Thinks: Hmmmmmm??? Sounds like another opportunity for Geezer Enterprises, Inc. The Micronucleator. Only $19.95, plus shipping and handling.

But wait, there's more! If you order your Mironucleator within the next sixty minutes, we'll include a second one FREE!

Title: I had an explosion with my cocoa. Why?
Post by: Karen W. on 23/04/2011 08:34:10

Frankly I have never microwaved Sparkling Perrier water before... Wouldn't that cause more eruption when you stir it up..? Kind of like shaking it in the bottle?

Title: I had an explosion with my cocoa. Why?
Post by: Bored chemist on 23/04/2011 11:08:35

"plus you can leach out the plasicisers from the plastic itself."
For a start I doubt plastic spoons have a lot of plasticisers in then (they are meant to be rigid) and for an encore, why would it matter if the plasticisers leached out?

Title: I had an explosion with my cocoa. Why?
Post by: Mazurka on 13/05/2011 14:53:50

Are you sure it was not Volvic - famously filled with volcanicity?

Title: I had an explosion with my cocoa. Why?
Post by: SeanB on 14/05/2011 13:04:28

Most plastic spoons are made from styrene monomer, and this is not really a good thing to ingest, as it is an estrogen mimic. OK if you are a woman and want to please without seeing a plastic surgeon, but not good otherwise.

Title: I had an explosion with my cocoa. Why?
Post by: mattyh on 14/05/2011 17:31:34

Quote from: Bored chemist on 23/04/2011 11:08:35

"plus you can leach out the plasticisers from the plastic itself."
For a start I doubt plastic spoons have a lot of plasticisers in then (they are meant to be rigid) and for an encore, why would it matter if the plasticisers leached out?

There's the possibility they are carcinogenic. I rarely use plastic now for cooking purposes.  I heard that cling film or saran wrap is real bad, dunno how true that is though.