Boiling

The boiling point of water is 100 °C or 212 °F but is lower with the decreased atmospheric pressure found at higher altitudes.

Boiling water is used as a method of making it potable by killing microbes and viruses that may be present.

The lowest heat flux seen in boiling is only sufficient to cause [natural convection], where the warmer fluid rises due to its slightly lower 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.

Since this vapour film is much less capable of carrying heat away from the surface, the temperature rises very rapidly beyond this point into the transition boiling regime.

The point at which this occurs is dependent on the characteristics of boiling fluid and the heating surface in question.

As a method of disinfecting water, bringing it to its boiling point at 100 °C (212 °F), is the oldest and most effective way since it does not affect the taste, it is effective despite contaminants or particles present in it, and is a single step process which eliminates most microbes responsible for causing intestine related diseases.

The heat sensitivity of micro-organisms varies, at 70 °C (158 °F), Giardia species (which cause giardiasis) can take ten minutes for complete inactivation, most intestine affecting microbes and E. coli (gastroenteritis) take less than a minute; at boiling point, Vibrio cholerae (cholera) takes ten seconds and hepatitis A virus (causes the symptom of jaundice), one minute.

Boiling does not ensure the elimination of all micro-organisms; the bacterial spores Clostridium can survive at 100 °C (212 °F) but are not water-borne or intestine affecting.

[8] The traditional advice of boiling water for ten minutes is mainly for additional safety, since microbes start getting eliminated at temperatures greater than 60 °C (140 °F) and bringing it to its boiling point is also a useful indication that can be seen without the help of a thermometer, and by this time, the water is disinfected.

[13] Simmering is gentle boiling, while in poaching the cooking liquid moves but scarcely bubbles.

High elevation cooking generally takes longer since boiling point is a function of atmospheric pressure.

[citation needed] Also known as "boil-in-bag", this involves heating or cooking ready-made foods sealed in a thick plastic bag.

The bag containing the food, often frozen, is submerged in boiling water for a prescribed time.

[17] The resulting dishes can be prepared with greater convenience as no pots or pans are dirtied in the process.

When a liquid reaches its boiling point bubbles of gas form in it which rise into the surface and burst into the air.