Why do bubbles form when we hit the surface of water?

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Discussion Overview

The discussion centers around the phenomenon of bubble formation when an object hits the surface of water, particularly in the context of swimming pools. Participants explore the underlying physics and mechanics of this occurrence, considering factors such as air displacement and the role of surfactants.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant notes that bubbles typically do not form on the water's surface unless a surfactant is present.
  • A reference to the Marangoni effect is provided, although its relevance to the specific situation is questioned.
  • Another participant suggests that when an object hits the water, air trapped between the object and the surface is forced underwater, leading to bubble formation.
  • It is mentioned that as the object submerges, air and water rush to fill the space above, potentially trapping air underneath the water, contributing to bubble formation.
  • A participant adds that air trapped in swimwear may also escape and contribute to the bubbles observed.
  • One participant expresses gratitude for the explanations and clarifies that no surfactant was present in the water.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the necessity of surfactants for bubble formation, as some suggest that bubbles can form without them due to air displacement. The discussion remains open with multiple viewpoints presented.

Contextual Notes

There are assumptions about the conditions under which bubbles form, such as the presence of surfactants and the specific mechanics of air displacement, which are not fully resolved.

Adamuss
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Recently I went to a pool, and observed that when we hit the water/ create waves on the top layer of it, bubbles emerge.

It may sound like a silly question, but it really got stuck in my mind..Why does this happen?

Thank you for your answers in advance.

P.S: I am new to this forum, I hope that I opened this thread in the right section.
 
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Normally bubbles won't form on the surface unless there's some sort of surfactant (soap) involved.
 
Adamuss said:
Recently I went to a pool, and observed that when we hit the water/ create waves on the top layer of it, bubbles emerge.
<snip>

Are you referring to foam?
 
Adamuss said:
Recently I went to a pool, and observed that when we hit the water/ create waves on the top layer of it, bubbles emerge.

It may sound like a silly question, but it really got stuck in my mind..Why does this happen?

Thank you for your answers in advance.

P.S: I am new to this forum, I hope that I opened this thread in the right section.

You chose the right forum, and there's nothing silly about this sort of question - the physics of a good-sized object (chances are that you weigh many tens of kilograms) hitting water are complicated and interesting. Google might find you some high-speed images and videos of what's going on.

Several things to consider: First, as you are about to hit the water, the air between you and the surface will not be able to escape before you reach the surface - that air will be driven under water and will have to make it back to the surface as bubbles. Second, as you push below the surface, both air and water will rush into fill the space above you, and some of the air may end up underneath the water - another source of bubbles. And as KL7AJ points out, any surfactant (or even surface contaminant) in the water will affect how long the bubbles last and how noticeable they are.
 
Don't forget that some air is also trapped inside your bathing suit, and has to escape.

Chet
 
Thank you for your answers, there was no surfactant in the water, so I understood what happened, reading Nugatory's explanation.
 

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