Boiling fresh corn

On this Wikipedia the language links are at the top of the page across from the article title. There are two main types of boiling: nucleate boiling where boiling fresh corn bubbles of vapour form at discrete points, and critical heat flux boiling where the boiling surface is heated above a certain critical temperature and a film of vapor forms on the surface.

Boiling water is used as a method of making it potable by killing microbes and viruses that may be present. Boiling water is also used in several cooking methods including boiling, steaming, and poaching. The lowest heat flux seen in boiling is only sufficient to cause , where the warmer fluid rises due to its slightly higher density. This condition occurs only when the superheat is very low, meaning that the hot surface near the fluid is nearly the same temperature as the boiling point. A video showing water being boiled.

In general, the number of nucleation sites is increased by an increasing surface temperature. Homogeneous nucleation, where the bubbles form from the surrounding liquid instead of on a surface, can occur if the liquid is warmer in its center, and cooler at the surfaces of the container. This can be done, for instance, in a microwave oven, which heats the water and not the container. Transition boiling may be defined as the unstable boiling, which occurs at surface temperatures between the maximum attainable in nucleate and the minimum attainable in film boiling. The formation of bubbles in a heated liquid is a complex physical process which often involves cavitation and acoustic effects, such as the broad-spectrum hiss one hears in a kettle not yet heated to the point where bubbles boil to the surface. If a surface heating the liquid is significantly hotter than the liquid then film boiling will occur, where a thin layer of vapor, which has low thermal conductivity, insulates the surface. This condition of a vapor film insulating the surface from the liquid characterizes film boiling.

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