Home > Science > Features > Inventing Our World > In the Bathroom > Bubbles |
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In the Bathroom
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Air bubbles dive into water following the momentum of the flow from the tap. |
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Then, what is soap? Soap is a big molecule, composed of two parts, one likes water, the other doesn't.
When gently mixed with water, soap molecules gather on the surface so that the hydrophobic parts - the parts that don't like water - can escape water contact.
Sooner or later, the surface will be fully occupied by soap molecules. Unlucky molecules will have to find another way to escape water contact. Air bubbles, created under the tap, are perfect for that.
They get surrounded by soap molecules and, because air is lighter than water, the bubbles want to get back up to the surface.
Then, on the way up the air bubble with soap surrounding it meets the water surface, which is filled with other soap molecules.
And this is how a soap bubble is created. It's a sphere of air,surrounded by a layer of water that is trapped between soap molecules.
This would be nice but soap bubbles can't fly. The weight of the bubble, including its air, water and soap, is heavier than the weight of the same volume of air (even without the duck). Hence, following Archimedes' principle, bubbles can't fly.
Find out more about floating and sinking in floating duck chapter.
