A bubble in water is a pocket of gas
surrounded by liquid water. The gas pressure
pushes against the water nearly equally in all
directions so bubbles are generally
approximately spherical. Since the gas is less
dense than the water, it rises to the top. When
the bubble reaches the surface of the water,
sometimes the surface tension keeps it trapped
There are many different reasons that bubbles
form in water.
Carbonation - Carbonated water involves carbon
dioxide dissolved in water at high pressures.
When the pressure is released (e.g. a beverage
container is opened), some of the dissolved
carbon dioxide comes out of solution and
Boiling - When water boils, it undergoes a
phase change from a liquid to a gas. As the
transition takes place, gaseous water molecules
collect together (nucleate) within the liquid
and form bubbles.
Chemical reaction - If an aqueous chemical
reaction that produces a gas takes place, it
will also create bubbles in water.
Soap - Soap itself does not create bubbles,
but it acts as a surfactant in water, reducing
the surface tension and allowing bubbles to form
more easily and persist longer since they are
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