Why does foam form on orange squash?

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Discussion Overview

The discussion centers around the phenomenon of foam formation on orange squash compared to plain water. Participants explore the underlying reasons for the observed differences in bubble behavior when water is mixed with squash, touching on aspects of chemistry and fluid dynamics.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant notes that foam forms on squash but not on plain water, raising questions about the underlying causes.
  • Another suggests that viscosity differences between squash and water might play a role in foam formation.
  • It is proposed that surfactants in the squash could lower the surface tension of water, allowing for more stable bubbles, similar to soap.
  • A participant elaborates that surfactants may not create bubbles but help contain air bubbles due to lower surface tension, while also expressing confusion over the presence of citric acid and its effects on bubbling.
  • One participant argues against the role of surfactants, proposing that oils in the cordial stabilize bubbles due to their hydrophobic nature.
  • Another participant counters the oil argument, suggesting that light oils might destabilize foaming due to differing surface tensions.

Areas of Agreement / Disagreement

Participants express differing views on the role of surfactants and oils in foam formation, indicating that there is no consensus on the primary factors responsible for the observed phenomenon.

Contextual Notes

Participants mention various ingredients such as citric acid and oils without resolving how these components interact with foam formation. The discussion also highlights the complexity of the chemistry involved, with some assumptions about the properties of the substances remaining unexamined.

wildwildebees
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Why do I get a foam forming on my glass of squash, but not just a glass of water?

i.e.

If I fill a glass with water from the tap, with the water flowing pretty fast, there are only a very few, quite large, bubbles which form on the surface of the water, and they quickly dissipate away.

If I add a small amount of squash (cordial) to the bottom of the glass and then add the water in the same way, a large number of small bubbles (a foam, I suppose) forms on the surface, and takes 3 or 4 seconds to disappear.

Anyone know what's responsible for the difference? It seems related to a soap foam, but I wouldn't have thought there any any ingredients in common...

Cheers!
 
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Hmm. Could it have something to do with the viscosity of the substance compared to water?
 
And/or
One agent needed to produce foam is a surficant which lowers the surface tension of water. Some ingrediant in the sqaush could midly be providing this feature, So in essence the action is the same as a soap. You could search for more information about foam, suficants, foaming agents.
 
Yes surfactants - presumably these don't actually create bubbles but just allow any air bubbles which enter the liquid to be contained? Since the surface tension is lower, so the restoring force which acts to close the bubble to reduce surface area is lower.

I've had a look around to see what the surfactants could be and couldn't find much - citric acid is present in 3 different liquids I tested, but then I also tried pure lemon juice and that didn't bubble at all! Also, milk does create bubbles. Very confusing. But I suppose this is really getting into chemistry now.
 
Not surfactants in fact quite the opposite - oils.

the cordial contains oils (in fact that's what gives the flavouring and smell of orange)

The oil is hydrophobic and so stabilise the bubble.

Regards

Sam
 
sambristol said:
Not surfactants in fact quite the opposite - oils.

the cordial contains oils (in fact that's what gives the flavouring and smell of orange)

The oil is hydrophobic and so stabilise the bubble.

Regards

Sam

I was under the impression that light oils, having a different surface tension than water, de-stabilise foaming.
 

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