Naked Science Forum
Non Life Sciences => Chemistry => Topic started by: thedoc on 05/11/2015 21:50:02
-
Ian McDonald asked the Naked Scientists:
I poured a soda water I made with a soda stream at home into 2 glasses. One had vertical walls and the other had sloped walls and the bubbles stayed on the vertical walls and the other glass looked totally flat. Was it the glass surface or the slope? I convinced myself that it was the slope by pouring into a variable sloped wine glass and it stuck to the vertical wall and not the base but some persons in our house still say it is the surface and not the slope as sections of the glass could be made to create this effect or we clean the sides to make if rougher.
What do you think?
-
The bubbles in soda is dissolved CO2. When the pressure is released, by opening the bottle, the amount of the CO2 that can remain dissolved goes down, causing bubbles of CO2 come out of solution.
When bubbles form, what is happening is a phase change from one component system, into a two component system. Going from one to two phases is not always a clean transition but can do something similar to super saturation, where there is a inhibition to the change. The walls of the glass are acting as nucleation centers, lowering the activation energy allowing the phase change to occur.
If you took sugar and hot water and kept adding sugar, eventually the sugar will form a saturated solution. If we slowly cool only the hot sugar water, we can form a super saturated solution. This is where we can more sugar dissolved, than should it be at the cool temperature. If we sprinkle a little sugar into the sugar water, these will act like nucleation centers and cause all the excess sugar to fall out.
In your case the soda is saturated with CO2, and something on the glass is acting like a nucleation center to allow CO2 to come out easier.