If you spend enough time near the water, you've probably encountered sea foam, a frothy material that gathers in breaking waves and occasionally washes up on beaches. You may even compare it to old-fashioned bubble baths! However, what actually creates foam? How does it get to the shorelines? As we all have guessed, air bubbles, stirred up in water can easily merge, especially when it’s pure, but why do they merge much more slowly in sea water or in other liquids containing dissolved impurities, which is the reason why persistent foam is produced
Since enduring foams are frequently formed in solutions with high electrolyte concentrations, scientists have long hypothesized that dissolved electrolytes may impede bubble mergers. Subtle force is generated by the electrolyte, mobile ions created when substances dissolve in liquid. When two bubbles collide, these forces greatly reduce the speed at which the liquid separating the bubbles can flow, which could explain why foam easily forms in salty seawater.
This being said, a number of tests have been conducted to determine how electrolytes impact bubble mergers. They made an air bubble at the tip of a glass capillary by submerging its end beneath a liquid surface. The bubble was then accelerated downhill until it combined with a bubble that was affixed to a silica surface below. The scientists used interferometry to detect the liquid film's thickness and track it as it shrank until it was zero.
The interferometric light signal for merging air bubbles in clear water (left), a salt solution (middle), and a sugar solution (right) is displayed in the three panels. Each time the bubbles approach and join, the disk or ring grows and vanishes. The researchers discovered that this impact delays the film drainage just enough to postpone film rupture and ultimate bubble merging in exact accord with the results. In summary, by extending the lifespan of the thin liquid sheet, electrolytes significantly slow down the coalescence of bubbles.
Finally, I hope that the next time you go to the beach or see the sea, you will have at least a vague idea of what is going on with that foamy sea stuff that tickles you, because after all, curiosity is the link between us and the world around us, and wholeness is the key to everything.
Fun fact:
A king tide with 25-foot (almost 8-meter) waves in Washington state during the winter of 2020 produced a "blender effect" that stirred up sea foam as high as a man's chest. Sea foam is produced in large quantities when the weather is absolutely out of control.
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