2 Answers

  1. Andrey Sanin, Professor, Doctor of Physical and Mathematical Sciences, Associate of the Institute of Physics of Peter the Great St. Petersburg Polytechnic University, explains:

    A pot of milk is filled with gas bubbles that do not burst.

    To begin with, it is necessary to understand how many small air bubbles appear at all when boiling. It is impossible to notice the approach of this phase in opaque milk. And in the case of water, the process is clear, especially if you watch it through a transparent vessel. As you heat up, that is, as the temperature increases, you will see that the bottom and walls of the vessel are covered with small gas bubbles. They are formed by the release of gases dissolved in water. In the thin bottom layer, the temperature is slightly higher, and the water, in theory, should evaporate more intensively. Only where does it evaporate in the depths? It finds a way out-it evaporates inside tiny bubbles. They always form between the vessel wall and the liquid, especially where there are traces of fat or small scratches, invisible to the eye microcracks.

    As the temperature rises, the bubble gradually expands until the pressure of air and steam inside it is balanced by the external pressure. Finally, the buoyant force pulls it away and it floats up. And a new one is already maturing on the wall.

    Milk, in addition to water, contains long polymer molecules. When water evaporates from near-surface layers when milk is heated, these molecules bond and form a strong film. Meanwhile, tiny bubbles appear at the bottom — this is the release of gas dissolved in the liquid. Water also begins to evaporate inside the bubbles, they grow, and their walls are reinforced with a polymer film. When the bubbles pop up, they rest against the film on the surface and can not, as in water, burst and release steam. As the milk approaches the boiling point, the number of bubbles increases, they form a foam that lifts the polymer film. At the same time, the bubbles themselves are quite strong and do not burst. Propped up from the bottom with new ones, they quickly overflow the pan.

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  2. Do not be afraid ,it will not run far, maximum on the floor .

    If you are interested in the “escape “process:

    It's all a physical and chemical process .

    When a container of milk is heated, the water (which is in the milk ) begins to form bubbles (this can be noticed when heating ordinary water )

    And complex polymer structures in milk form a “film” on the surface ,so the bubbles have nowhere to go and they accumulate under the film .While the heating continues, according to the law of physics, the gas expands at increasing t°, which means that a bunch of small bubbles pushes the “film” to form a foam that tends upwards� .And then as if on a roll, milk on the floor, you with a rag, screams, mats .

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