Boiling (also called ebullition), a type of phase transition, is the rapid vaporization of a liquid, which typically occurs when a liquid is heated to its boiling point, the temperature at which the vapor pressure of the liquid is equal to the pressure exerted on the liquid by the surrounding environmental pressure. In Thermodynamics, phase transition or phase change is the transformation of a thermodynamic system from one phase to another Evaporation is the process by which Molecules in a Liquid state (e Liquid is one of the principal States of matter. A liquid is a Fluid that has the particles loose and can freely form a distinct surface at the boundaries of The boiling point of a liquid is the temperature at which the Vapor pressure of the liquid equals the environmental pressure surrounding the liquid Temperature is a physical property of a system that underlies the common notions of hot and cold something that is hotter generally has the greater temperature Vapor pressure (also known as equilibrium vapor pressure or saturation vapor pressure) is the Pressure of a Vapor in equilibrium Thus, a liquid may also boil when the pressure of the surrounding atmosphere is sufficiently reduced, such as the use of a vacuum pump or at high altitudes. A vacuum pump is a device that removes gas molecules from a sealed volume in order to leave behind a partial Vacuum. High altitude are regions on the Earth 's surface (or in its atmosphere) that are high above Mean sea level. Boiling occurs in three characteristic stages, which are nucleate, transition and film boiling. These stages generally take place from low to high surface temperatures, respectively.

Contents 1 Nucleate boiling 2 Transition boiling 3 Film boiling 4 Boiling in cookery 5 Boiling for water purification 6 See also 7 See also

Nucleate boiling

Nucleate boiling is characterized by the incipience and growth of bubbles on a heated surface, which rise from discrete points on a surface, whose temperature is only slightly above the liquid’s saturation temperature. The boiling point of a liquid is the temperature at which the Vapor pressure of the liquid equals the environmental pressure surrounding the liquid In general, the number of nucleation sites are increased by an increasing surface temperature. Nucleation is the onset of a Phase transition in a small region An irregular surface of the boiling vessel (i. e. increased surface roughness) can create additional nucleation sites, while an exceptionally smooth surface, such as glass, lends itself to superheating. See Superheater for the device used in Steam engines In Physics, superheating (sometimes referred to as boiling retardation Under these conditions, a heated liquid may show boiling delay and the temperature may go somewhat above the boiling point and fail to boil. See Superheater for the device used in Steam engines In Physics, superheating (sometimes referred to as boiling retardation

Transition boiling

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 roil the surface. Soda bubbles macrojpg|right|thumb|Bubbles of Gas in a Soft drink]] A bubble is a globule of one substance in another usually Gas in a Liquid Cavitation is defined as the phenomenon of formation of vapour bubbles of a flowing liquid in a region where the pressure of the liquid falls below its vapour pressure

Film boiling

Main article: Leidenfrost effect

If a surface heating the liquid is significantly hotter than the liquid then film boling will occur, where a thin layer of vapour, which has low thermal conductivity insulates the surface. The Leidenfrost effect is a Phenomenon in which a liquid in near contact with a mass significantly hotter than its Boiling point, produces an insulating Vapor In Physics, thermal conductivity, k is the property of a material that indicates its ability to conduct Heat. This condition of a vapor film insulating the surface from the liquid characterizes film boiling.

Boiling in cookery

In cookery, boiling is cooking food in boiling water, or other water-based liquid such as stock or milk. Cooking is the process of preparing Food by applying Heat, selecting measuring and combining of ingredients in an ordered procedure for producing safe and edible Water is a common Chemical substance that is essential for the survival of all known forms of Life. Stock is a flavoured liquid It forms the basis of many dishes particularly Soups and Sauces Stock is prepared by simmering various ingredients in water including Milk is an opaque white liquid produced by the Mammary glands of female Mammals (including Monotremes. Simmering is gentle boiling, while in poaching the cooking liquid moves but scarcely bubbles. Simmering is a Cooking technique in which Foods are cooked in hot liquids kept at or just barely below the boiling point of Water (at average sea level Poaching is the process of gently Simmering food in liquid generally Water, stock or Wine.

The open-air boiling point of water is typically considered to be 100 C degrees. The boiling point of a liquid is the temperature at which the Vapor pressure of the liquid equals the environmental pressure surrounding the liquid Pressure and a change in composition of the liquid may alter the boiling point of the liquid. For this reason, high elevation cooking generally takes longer since boiling point is a function of atmospheric pressure. The elevation of a Geographic location is its height above a fixed reference point often the mean sea level. In Denver, Colorado, which is at an elevation of about one mile, water boils at approximately 95 C. The City and County of Denver (pronounced /ˈdɛnvɚ/ is the Capital and the most populous city of Colorado, in the United States A mile is a unit of Length, usually used to measure Distance, in a number of different systems including Imperial units United States [1] Depending on the type of food and the elevation, the boiling water may not be hot enough to cook the food properly. Similarly, increasing the pressure as in a pressure cooker raises the temperature of the contents above the open air boiling point.

Adding a water soluble substance, such as salt or sugar also increases the boiling point. Solubility is the characteristic Physical property referring to the ability of a given substance the Solute, to dissolve in a Solvent. Salt is a Dietary mineral composed primarily of Sodium chloride that is essential for Animal life but toxic to most land plants Sugar is a class of edible Crystalline substances mainly Sucrose, Lactose, and Fructose. This is called boiling-point elevation. Boiling-point elevation describes the phenomenon that the Boiling point of a Liquid (a Solvent) will be higher when another compound is added meaning that However, the effect is very small, and the boiling point will be increased by an insignificant amount. On the other hand, salt or ethylene glycol can cause significant freezing point depression. Ethylene glycol ( monoethylene glycol ( MEG) 12-ethanediol, IUPAC name: ethane-12-diol) is an Alcohol with two -OH Freezing-point depression describes the phenomenon that the freezing point of a Liquid (a Solvent) is depressed when another compound is added meaning Due to variations in composition and pressure, the boiling point of water is almost never exactly 100 C, but rather close enough for cooking.

In places where the available water supply is contaminated with disease-causing bacteria, boiling water and allowing it to cool before drinking it is a valuable health measure. Water supply is the process of self-provision or provision by third parties of water of various qualities to different users The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have Boiling water for a few minutes kills most bacteria, amoeba, and other microbial pathogens. Amoeba (sometimes amœba or ameba, plural amoebae) is a Genus of Protozoa that moves A pathogen (from Greek πάθος pathos "suffering passion" and γἰγνομαι (γεν- gignomai (gen- "I give birth to" infectious It thus can help prevent cholera, dysentery, and other diseases caused by microorganisms. Cholera, sometimes known as Asiatic cholera or epidemic cholera, is an infectious Gastroenteritis caused by the Bacterium Dysentery (formerly known as flux or the bloody flux) is an infection of the digestive system that results in severe Diarrhea containing mucus and blood A microorganism (also spelled micro organism or micro-organism and also called a microbe) is an Organism that is Microscopic (usually

Foods suitable for boiling include fish, vegetables, farinaceous foods such as pasta, eggs, meats, sauces, stocks and soups.

Boiling has several advantages. It is safe and simple, and it is appropriate for large-scale cookery. Older, tougher, cheaper cuts of meat and poultry can be made digestible. Nutritious, well flavoured stock is produced. Also, maximum color and nutritive value is retained when cooking green vegetables, provided boiling time is kept to the minimum.

On the other hand, there are several disadvantages. There is a loss of soluble vitamins from foods to the water, and boiled foods can look unattractive. Boiling can also be a slow method of cooking food.

Boiling can be done in two ways: The food can be placed into already rapidly boiling water and left to cook, the heat can be turned down and the food can be simmered; or the food can also be placed into the pot, and cold water may be added to the pot. This may then be boiled until the food is satisfactory.

Water on the outside of a pot, i. e. a wet pot, increases the time it takes the pot of water to boil. The pot will heat at a normal rate once all excess water on the outside of the pot evaporates.

Boiling for water purification

Boiling is used as a method of water purification. Water purification is the process of removing contaminants and other harmful microorganisms from a raw water source Boiling is commonly advocated as an emergency water treatment method, or as a method of portable water purification in rural or wilderness settings without access to a potable water infrastructure. Portable water purification devices — also known as point-of-use (POU water treatment systems and field water disinfection techniques — are self-contained

See also

• Phase diagram
• Phase transition

See also

In Physical chemistry, Mineralogy, and Materials science, a phase diagram is a type of graph used to show the equilibrium conditions In Thermodynamics, phase transition or phase change is the transformation of a thermodynamic system from one phase to another

© 2009 citizendia.org; parts available under the terms of GNU Free Documentation License, from http://en.wikipedia.org
Dapyx Software network: MP3 Explorer | Ebook Manager | Zenithic