Soap bubble physics are stunning

Soap bubble physics are stunning

Bubbles are everywhere. They do not just fascinate individuals. Science is also looking into it with great attention. Their physique is indeed particular: a new study highlights one of these particularities.

At New Year, the bubbles are (moderately) in champagne. But they are actually everywhere, every day. In carbonated water, of course, but also when you use soap, in children’s bubble guns, and in many other circumstances such as condensation on the windows in case of humidity. Many researchers are interested to their physique — which is quite amazing.

The latest study, published on December 19, 2022, is signed by a group of French scientists, based at the University of Paris-Saclay. François Boulogne, Frédéric Restagno and Emmanuelle Rio have studied the surface temperature variations of bubbles.

8 degrees difference between bubble and ambient temperature

The temperature variation identified in this publication is not the least: on the surface of a bubble, the very delicate film that constitutes it can go down to 8 degrees Celsius below the ambient temperature. The French team therefore put the bubbles to the test by preparing a cocktail of washing-up liquid, water and glycerol, whose composition and exposure conditions they regularly modified. The objective is to understand this cooling and its potential extent.

Bubbles form on all sorts of occasions. // Source: Pexels

When we sweat, we lose water by evaporation: this serves to cool the body. The same thing happens in a bubble, which loses liquid by evaporation, releasing energy. The temperature of the bubble therefore begins by falling during this process (until this difference of 8 degrees), but then it rises until it reaches ambient temperature. The French scientists have also noticed that two parameters change the extent of the variation: the ” relative humidity » of the place and the « initial concentration of glycerol “.

Based on these discoveries, the research team was able to build a model of the formation and evolution of bubbles (and more generally of the soapy “films” that can form). ” We emphasize that this cooling effect is significant and should be carefully considered in future studies of soap film dynamics. “say the scientists. Yes, because bubbles can be involved in many manufacturing processes on an industrial scale: understanding their evolution is also a matter of their mastery.

But there is also something to marvel at in all of this. The next time you brush your hand against a soap bubble, while washing the dishes, for example, you will know that an amazing physical mechanism is taking place under your hand. And a mechanism of which we are only now beginning to understand certain elements: this study is the first of its kind regarding the temperature variations of bubbles.

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