Naked Science Forum

Non Life Sciences => Chemistry => Topic started by: thedoc on 04/12/2016 04:53:02

Title: Does cocoa powder fortify the walls of a bubble? Why are bubbles coated in cocoa able to be picked up on a spoon?
Post by: thedoc on 04/12/2016 04:53:02

Miranda Norlin asked the Naked Scientists:
   Hello Naked Scientists,
While making my cocoa this morning, I noticed an interesting phenomenon. When I make cocoa I use milk and baking cocoa rather than the formula you get at the store and water. When I pour the milk into the pot it foams. Then, when I put the heaping spoonful of baking cocoa in, the bubbles get covered on the top with a thin layer of cocoa. The milk must be cold or else it melts the cocoa and the whole thing doesn't work. When the bubbles are covered, you can roll them with a spoon onto the other cocoa that is floating in heaps all around the pot. After you gently roll it around for a bit, you have a cocoa-coated orb that is just air inside but can be picked up on a spoon.

I am guessing this is because the cocoa fortifies the walls of the bubble. Could you tell me if this is correct? By the way the podcast is great. I listen to it while I am "cleaning" my room.

Thanks a lot,
       Miranda

What do you think?

Title: Re: Does cocoa powder fortify the walls of a bubble? Why are bubbles coated in cocoa able to be pic
Post by: ProjectSailor on 05/12/2016 10:20:01

Pretty much spot on..

The cocoa powder obviously has an impact on the surface tension of the milk making these bubbles tough to break.

If you sprinkle some on top of a cappucino, if you notice the foam drops more rapidly where you havent sprinkled it..