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Name: Juliette S.
Status: student
Age: 10
Location: N/A
Country: N/A
Date: Thursday, April 25, 2002


Question:
Do soap bubbles need air to be formed?


Replies:
Hello,

To form a bubble, some sort of a gas is needed. It is the gas pressure inside a bubble that keeps the thin film of the soup from collapsing. If you slowly drain the gas from inside of a bubble, the bubble shrinks. When the gas is entirely taken out, you end up with a tiny droplet of soap water.

Air is primarily nitrogen but you can use other gases for this purpose.

Ali Khounsary, Ph.D.


Soap bubbles require some gas inside the bubble. It need not necessarily be air but that is the most available gas around. Other gases may give different bubble behavior. For example: Helium will cause a bubble to rise in the air because helium is less dense than air, but the bubble will not last long because the helium diffuses rapidly across the bubble membrane. If the bubble is blown up with carbon dioxide, it will fall rapidly because it is more dense than air, but the bubble also will not long because carbon dioxide is soluble in the soap/water solution of the bubble.

Vince Calder



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