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What holds air bubbles in place?

Article 2 Module 1

In the first lesson, I identified the primary reason for the whiteness in natural objects.

When air bubbles of different sizes are trapped in a transparent material, the light is refracted in multiple directions. It is as if the light entered a hall with innumerable nano-sized mirrors at different angles to each other. Does that clarify why snow is blinding?

The air molecules are held hostage in different sized packets by a transparent netting. If the netting was not transparent, we would not get the effect of a pure white color coming back to us.

What kind of mesh or web holds air bubbles captive? There are three kinds.


1. Liquid, cold, or frozen water molecules 

ice cubes with central white cloud
white snow on deck

When water vapor molecules cool down, they form hydrogen bonds that are very sticky. Those hydrogen bonds bind water molecules together forming a strong net that holds air molecules captive.

Clouds


The white color is due to a reflection of white light off disorganized molecules of air held together in a web of liquid or frozen water. 

Liquid water splash - White water

For clouds and fog, water vapor molecules cool down at higher altitudes in the troposphere. This allows the formation of a web of connected vapor molecules. 

The web holds microscopic liquid water droplets intermingled with bubbles of air.

Air bubbles while diving
Water splashes - white water
Blanket of fog

2. Proteins 

Spitting crab
Whipped egg whites
White air bubbles beer

There are proteins released in the liquid of the crab's saliva; similarly there are proteins in egg whites and in beer foam. Mynah bird feathers and polar bear fur are made of keratin which is also a protein.

White snow/white Mynah bird


All the instances show proteins helping forming a transparent mesh or tube that entraps air molecules in one position.

White polar bear

Adding cohesive molecules to foamy liquids makes the foaming bubbles last longer. This is the reason sea foam is formed. Proteins from broken down biodegradable material, like algae, mixes with the water. Thin layers of protein and water hold countless bubbles in place. 

Lake foam

3. Fats or soaps 

Soapy foam on man's hand
white fluffy whipped cream
Overbubbles

Pockets of air are not only encompassed with water or proteins. Other natural materials hold air bubbles hostage. For example, molecules such as fats (whipped cream) and soaps are really good at this. Even glass can trap air bubbles.  


Fat globules of whipped cream: one needs at least 30% fat in cream to allow air bubbles to be held in place for a whipped texture. 

Giant soap bubble

In the instances above, fat or soap molecules form a transparent mesh that entraps air molecules. 

Transparent glass with air bubbles

Detergents/soap foams:  A white foam develops when we use soap to lather our hands. Contrast the picture of the white foam with its multitude chaotic mass of bubbles with the see-through single soap bubble shown here. 


Picture credits:

  1. F Delventhal. Ginger Ale. Flickr photo-sharing. Taken on April 30, 2010.
  2. Hijab, J. Ice cubes with entrapped air bubbles. Winter, 2018.
  3. Hijab, J. White snow on the deck. Winter 2018.
  4. Hijab, J. Snow wonderland. Winter 2019.
  5. Joao Alves. Clouds. Flickr photo-sharing, Taken on May 13, 2009.
  6. Horia Varlan. Splash made by a swimmer jumping into the sea. Flicker - photo sharing. Taken on Aug 5, 2009.
  7. Andreas Bjärlestam Bubbles . Flickr photo-sharing. Taken July 25, 2008.
  8. lpiepiora. Splash. Flickr photo-sharing. Taken Feb 23, 2006
  9. tracyshaun. blanket of fog pouring over the headlands. Flicker photo-sharing, taken on Oct 29, 2008.
  10. devra . Spittling crab in Morro State Park Marina. This crab was foaming at the mouth. Flickr photo-sharing. Taken July 5, 2010. 
  11. Scott Mindeaux. whipped_egg_whites. Flickr photo-sharing. Taken July 6, 2005. 
  12. Martin Garrido. Beer. Flickr - photosharing. Taken on Dec 27, 2011.
  13. Charles Barilleaux Bali Mynah. Flickr photosharing..March 31, 2014. 
  14. Jessica Merz. Polar bear. Flickr photo-sharing. Taken on Feb 20, 2006.
  15. James St. John. Lake foam along the shoreline of Storr's Lake (San Salvador Island, Bahamas) . Flickr photo-sharing; taken on March 24, 2007. ".... The dissolved organic matter (from biodegraded Algae) increases the surface tension of the water, so wind-induced wave agitation creates more trapped bubbles in the water, resulting in a relatively persistent foam."
  16. By jocic. Soapy foam on man's hand. Shutterstock. ID: 160713749.
  17. Brian Teutsch. Whipped cream. Flickr - photo sharing, taken on Nov 22, 2007.
  18. rjp. Overbubbles. Flickr photo-sharing, taken Oct 26, 2010. 
  19. elPadawan. Giant Soap Bubble: Giant soap bubble outside the New Yorker shop, Můstek subway station, Prague. Flickr photo-sharing. July 12, 2012.
  20. By LVV. Transparent glass ball with air bubbles inside on a blue background. Shutterstock. ID: 45809566.
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