When water is boiled, the dissolved oxygen gains thermal energy, becomes light, comes to the top as a bubble and bursts to go into the atmosphere. The evolution of gases is significant until most of them are removed.
Similarly, when milk is boiled, the d... moreWhen water is boiled, the dissolved oxygen gains thermal energy, becomes light, comes to the top as a bubble and bursts to go into the atmosphere. The evolution of gases is significant until most of them are removed.
Similarly, when milk is boiled, the dissolved gases move to the surface of the liquid in the form of bubbles. But they cannot burst to the atmosphere easily because of the layer of fat on milk. The bubbles moving to the top continue to push the fat layer due to their kinetic energy. They cannot burst since the pressure inside the bubble is less than that of the outside. When the fat layer surpasses the vessel walls, it results into the overflowing of milk. less
As milk heats, the water in its structure starts evaporating from the surface. This concentrates the
remaining fat and proteins (which are lighter than milk) into a thicker layer at the top of the pot.
This layer eventually becomes so thick that water vapour rising through the milk can't break through
very easily and gets trapped. ... moreAs milk heats, the water in its structure starts evaporating from the surface. This concentrates the
remaining fat and proteins (which are lighter than milk) into a thicker layer at the top of the pot.
This layer eventually becomes so thick that water vapour rising through the milk can't break through
very easily and gets trapped.
The layer is so uniform that you can't necessarily see what's boiling up right underneath, except in
little bubbles around the edges. Enough water vapor eventually collects that it raises the thickened
layer above it. If left to boil long enough, it breaks through pushing it over the top and the milk spills down. less
