different shape between evaporation in boiling
Answers
To begin with, i’ll talk about this two phenomena first.
When the liquid get heated, tiny vapor bubbles come out around the condensation nucleus in liquid, which could be air in water or ashes. Vapor has its pressure at certain temperature, which is called Saturated Vapor Pressure. When the vapor pressure is lower than the pressure that vapor bubbles received from out side, such as the air pressure (and the liquid pressure considering the depth of liquid, however, in most cases, the liquid pressure is much too low), the bubbles stay there and waiting. As long as the Saturated Vapor Pressure in vapor bubbles reach the same as air pressure, the vapor bubbles will unstoppablely expand and move up, and that’s how boiling works.
But for the evaporation, it occurs on the surface of liquid. The molecules of liquid move at the surface of liquid. Most of the molecules are trapped by intermolecular forces, whereas a few molecules escaped to the air as vapor. Meanwhile, some vapor molecules move back to the liquid surface and are trapped by the liquid again. So if the escaping rate is higher than the tracpping rate, this is how evaporation works. if you blow a liquid, the vapor on that area is gone, and the evaporation speeds up.
So the difference is:
1, boiling can occurs everywhere, depending on the heat source. Whereas evaporation only takes place at surface of the liquid.
2, boiling requires certain temperature at certain pressure, and continuous heating source, while evaporation works at any temperature and pressure.
3, evaporation is a slow and soft process, while boiling is violent and fast.
4. Wind and surface area affect evaporation. Wind and surface area do not affect boiling