What is the boiling process?

During heating, air bubbles appear at the bottom of the vessel C with water, in which there is water vapor evaporated there when the water is heated. As the temperature rises, the vapor pressure in the bubble increases, the bubble increases and at some point rises. At the top, the water temperature is lower and the bubble collapses. As the liquid warms up, the bubbles expand throughout the volume and burst, throwing steam into the atmosphere. The liquid is boiling.