Ever seen a bubble in the walls of a drinking glass?
Mar 04 2007, 11:59 AM
A bubble is a GAS trapped within a medium of denser material.
The physical boundary of a bubble is formed by the liquid medium through which it is passing. Once the bubble has finished passing through it may reach a place (such as the surface of boiling water) where the pressure that held it together is no longer present, the bubble will rapidly expand because the surface tension of the liquid medium is no longer able to contain it and "POP" goes the bubble.
There are instances of liquid bubbles. When oil and water are put together they do not mix. What happens is that because of the different densities and because the surface tension of each liquid is great, the liquids will remain apart and one will become a bubble(s) of liquid within the other.
"A bubble can exist because the surface layer of a liquid (usually water) has a certain surface tension, which causes the layer to behave somewhat like an elastic sheet."