Capillarity
Capillarity is defined as the degree to which a material or object containing minute openings or passages, when immersed in a liquid, will draw the surface of the liquid above the hydrostatic level.
We can use the concepts of capillarity to predict the equilibrium shape of an interface.
Consider a bubble (Fig. 2.4).
![](images/Fig04.jpg)
Figure 2.4. A bubble in equilibrium with its surroundings
is the pressure in the dispersed phase
is the pressure in the surrounding medium and,
is the radius of the bubble
At the interface, the pressures ( and ) on two sides are equal only for flat surfaces, i.e. when goes to infinity. For a curved surface, these will not be equal.
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