How does foam form and why does it disappear again?

Foam is a collection of soap bubbles. When the soapy water is surrounded on two sides, you can blow and get a bubble.

two sides of soap

Foam, for example, is the buildup of soap bubbles in dish water or shower water. For a soap bubble, we need soap or surfactants like those in washing up liquid.

What distinguishes surfactants? We know there are two different types of liquids: those that mix well with water – alcohol, for example – and those that don’t mix with water at all – and this includes fats and cooking oil.

The Soap or surfactants They now have the advantage that they have two sides: one The “water-loving” side and one more the “greasy” sidethat stays out of the water.

If you put a drop of the detergent in the water, it immediately spreads over the surface of the water as a very thin film. In this soap film, the hydrophilic side of the individual molecules is now pointing downward to the water, and the lipid side pointing away from the water, that is, upward. If we move this surface, the foam will appear in the form of many soap bubbles.

Bubble skin soap consists of three layers: soap – water – soap

This can be illustrated by thinking about soap bubbles that children make: they dip a “bubble ring” in soapy water so that a thin skin of soapy water forms inside the ring. The difference from the rinse water surface is that with the skin in the bubble ring, the soap film surrounds the water on both sides – like a sandwich. Outside is a soapy film, inside is water. And when you blow on it, a soap bubble forms.

The skin of a soap bubble consists of three layers: the inside and the outside of the soap, i.e., the pulling side, with water in between. The reason why this semi-spherical shape is perfect is that the sphere is the most economical shape: for a given amount of trapped air, the sphere requires the smallest surface area.

Also works without blowing: bubbles in bubble bath and dish water

When you allow water in, you disturb the surface of the soapy water. Air enters below the surface of the water. This air does not stay there for long, but rather rises in the form of bubbles. When air bubbles penetrate the surface of the water, they do the same thing as blowing soap bubbles: they take with them a layer of soapy water on the surface and form them into a bubble.

Economic nature: forms common borders rather than individual areas

However, the foam does not consist of pretty balls. This is due to the fact that several soap bubbles that initially form in the foam immediately grow together. Then nature returns to moderation again. Frugal means that many soap bubbles are trying to form a common boundary. And many irregular bubbles are created in the foam.

When the bubble burst

The reason the foam disappears is that the skin of the bubbles is made up of soapy water. This soapy water flows slowly, causing bubbles to burst.

When it comes to beer foam, proteins are involved

The physical principle is similar to beer foam, but the foam is caused not only by turbulence on the surface of the beer in the glass, but also by the rise of air bubbles. Beer contains carbon dioxide. When it rises, the air bubbles carry these substances that contain the protein found in beer.

Here is the second difference: the skin of bubbles in beer foam does not consist of soapy water, but of a substance containing protein. This is almost always the case with food. When we cook rice or beat eggs – there is always foam during cooking, the proteins are involved. But the physics is the same.

Leave a Comment