Witchy: "What the hell has Science to do with Science?"

1st CLIL Twin: ""They are often used as a children's plaything, but they can be fascinating for scientists too.

Structure
The bubble "skin" consists of a thin layer of water trapped between two layers of molecules, often soap.
These layers possess hydrophilic heads and hydrophobic tails. The hydrophilic heads are attracted to the thin water layer and keep the bubble intact. When the hydrophobic tails are agitated, the bubble pops.
1st CLIL Twin says:

A bubble can exist because the surface layer of a liquid (usually water) has a certain surface tension, which causes the layer to behave somewhat like an elastic sheet. However, a bubble made with a pure liquid alone is not stable and a dissolved surfactant such as soap is needed to stabilize a bubble. As the soap film stretches, the surface concentration of soap decreases, which causes the surface tension to increase.

 
  Bubbles' spherical shape is also caused by surface tension. The tension causes the bubble to form a sphere, as a sphere has the smallest possible surface area for a given volume. But this leads us to another important problem we can study through *bubbles watching*: the mathematical problem of minimal surfaces!"
Witchy: "Don't worry kids! The CLIL brothers will manage to make even this lesson easy for you. I promise! However, if you want to learn more about bubbles and surface tension you'd better visit Wikipedia, the world know on-line encyclopedia". However, next time will meet there will be an exciting test on bubbles and their surface tension... alas!!
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