What's the temperature water boils at?
Boiling
The boiling point of water is typically considered to be 100 °C or 212 °F. Pressure and a change in the 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. In Denver, Colorado, USA, which is at an elevation of about one mile, water boils at approximately 95 °C or 203 °F. 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.
Boiling
Some science suggests adding a water-soluble substance, such as salt or sugar also increases the boiling point. This is called boiling-point elevation. At palatable concentrations of salt, the effect is very small, and the boiling point elevation is difficult to notice and this is why experiments to prove this are considered inconclusive. However, while making thick sugar syrup, such as for Gulab Jamun, one will notice boiling point elevation. Due to variations in composition and pressure, the boiling point of water is almost never exactly 100 °C, but rather close enough for cooking.
Fahrenheit
The Fahrenheit scale is a temperature scale based on one proposed in 1724 by Dutch–German–Polish physicist Daniel Gabriel Fahrenheit (1686–1736). It uses the degree Fahrenheit (symbol: °F) as the unit. Several accounts of how he originally defined his scale exist. The lower defining point, 0 °F, was established as the freezing temperature of a solution of brine made from equal parts of ice, water and salt (ammonium chloride). Further limits were established as the melting point of ice (32 °F) and his best estimate of the average human body temperature (96 °F, about 2.6 °F less than the modern value due to a later redefinition of the scale). The scale is now usually defined by two fixed points: the temperature at which water freezes into ice is defined as 32 °F, and the boiling point of water is defined to be 212 °F, a 180 °F separation, as defined at sea level and standard atmospheric pressure.
Superheated water
The solubility of gases in water is usually thought to decrease with temperature, but this only occurs to a certain temperature, before increasing again. For nitrogen, this minimum is 74 °C and for oxygen it is 94 °C
Gases are soluble in superheated water at elevated pressures. Above the critical temperature, water is completely miscible with all gasses. The increasing solubility of oxygen in particular allows superheated water to be used for wet oxidation processes.
Properties of water
Water has a very high specific heat capacity of 4.1814 J/(g·K) at 25 °C – the second highest among all the heteroatomic species (after ammonia), as well as a high heat of vaporization (40.65 kJ/mol or 2257 kJ/kg at the normal boiling point), both of which are a result of the extensive hydrogen bonding between its molecules. These two unusual properties allow water to moderate Earth's climate by buffering large fluctuations in temperature. Most of the additional energy stored in the climate system since 1970 has accumulated in the oceans.
Leiden scale
It has been reported that the scale is the kelvin scale shifted so that the boiling points of hydrogen and oxygen become zero and 70 respectively, but this is unlikely to be true. Oxygen under a standard atmosphere boils at a temperature in the 90.15 to 90.18 K range. For hydrogen, it depends on the molecular variety. The boiling point is 20.390 K for "normal" hydrogen (made up of 75% orthohydrogen and 25% parahydrogen) and 20.268 K for pure parahydrogen. Under the purported definition, absolute zero would lie at -20.15 °L.
Water
Water is a liquid at the temperatures and pressures that are most adequate for life. Specifically, at a standard pressure of 1 atm, water is a liquid between . Increasing the pressure slightly lowers the melting point, which is about at 600 atm and at 2100 atm. This effect is relevant, for example, to ice skating, to the buried lakes of Antarctica, and to the movement of glaciers. (At pressures higher than 2100 atm the melting point rapidly increases again, and ice takes several exotic forms that do not exist at lower pressures.)
Diamond tetra
The water should be very soft and a pH of 6 is preferable. A temperature of 28 degrees C (79 degrees F) is suitable.
Boiling point
where:
Temperature
The International System of Units (SI) defines a scale and unit for the kelvin or thermodynamic temperature by using the reliably reproducible temperature of the triple point of water as a second reference point (the first reference point being at absolute zero). The triple point is a singular state with its own unique and invariant temperature and pressure, along with, for a fixed mass of water in a vessel of fixed volume, an autonomically and stably self-determining partition into three mutually contacting phases, vapour, liquid, and solid, dynamically depending only on the total internal energy of the mass of water. For historical reasons, the triple point temperature of water is fixed at 273.16 units of the measurement increment.
Heat index
where
Bílinská kyselka
Bílinská kyselka (in English: Biliner, "Bílina acidulous water") is strongly mineralized alkaline bicarbonate (i.e. 5 to 7 grams per litre) mineral water from Bílina city (Czech Republic). Particularly sodium, potassium, calcium, magnesium, and iron are present as cations, as are anions of chloride, sulfate, and bicarbonate. The temperature of spring water ranges between 17 and 20 °C. (63 - 68 °F). Due to the high content of free carbon dioxide is naturally carbonated and packaged without additional chemical modifications. Water is collected from a borehole from a depth of 191 m under the mountain Bořeň. Biliner is available in Europe in one liter and 500 ml bottles. Biliner bottles are cobalt blue polyethylene terephthalate.
Lactococcus garvieae
Water temperature affects the disease seasonally as the climate changes, specifically when the water temperature is over . Infection is linked to water temperatures over 18 °C, although acute outbreaks have been discovered in water temperatures of 14–15 °C.
Boiling point
The boiling point of a liquid varies depending upon the surrounding environmental pressure. A liquid in a partial vacuum has a lower boiling point than when that liquid is at atmospheric pressure. A liquid at high pressure has a higher boiling point than when that liquid is at atmospheric pressure. For example, water boils at at sea level, but at at altitude. For a given pressure, different liquids will boil at different temperatures.
Smoke point
Standard Cooking Temperatures
Hydrothermal explosion
Hydrothermal explosions occur where shallow interconnected reservoirs of water at temperatures as high as 250° Celsius underlie thermal fields. Water usually boils at 100 °C, but under pressure its boiling point increases, causing the water to become superheated. A sudden reduction in pressure causes a rapid phase transition from liquid to steam, resulting in an explosion of water and rock debris. During the last Ice Age, many hydrothermal explosions were triggered by the release of pressure as glaciers receded. Other causes are seismic activity, erosion, or hydraulic fracturing.
Liquid air
The boiling point of liquid air is -194.35 °C, intermediate between the boiling points of liquid nitrogen and liquid oxygen. However, it can be difficult to keep at a stable temperature as the liquid boils, since the nitrogen will boil off first, leaving the mixture oxygen-rich and changing the boiling point. This may also occur in some circumstances due to the liquid air condensing oxygen out of the atmosphere.
Electrolysis of water
In the case of water electrolysis, Gibbs free energy represents the minimum "work" necessary for the reaction to proceed, and the reaction enthalpy is the amount of energy (both work and heat) that has to be provided so the reaction products are at the same temperature as the reactant (i.e. standard temperature for the values given above). Potentially, an electrolyser operating at 1.48 V would be 100% efficient.
Hydrohalite
Hydrohalite has a high nucleation energy, and solutions will normally need to be super cooled for crystals to form. The cryohydric point is at -21.2°C. Above this temperature liquid water saturated with salt can exist in equilibrium with hydrohalite. Hydrohalite has a strong positive temperature coefficient of solubility, unlike halite. Hydrohalite melts at 0.1°C. This is an incongruent melting point, as a liquid salty water, of different composition and solid halite is formed on melting. Under pressure, hydrohalite is stable between 7,900 and 11,600 atmospheres pressure. The melting point increases at the rate of 0.007°K per atmosphere. (for 1-1000 atmospheres). The maximum melting temperatures is at 25.8°C under 9400 atmospheres. Above this pressure the melting point reduces.
Scalding
It is recommended for the temperature of tap water not to exceed 38 — 45 °C to avoid discomfort and scalding. The technical implementation is complicated by the necessity to keep warm water at a temperature of 55 – 60 °C to inhibit the growth of legionella bacteria. 
Water hotter than 60 °C can induce scalding injuries within seconds, while it takes approximately 2 minutes to achieve an injury in 50 °C hot water.
Aix-les-Bains
The underground travel of the waters, from the opposite shore of the lake (more than thirty years at deep), explains its temperature of 46°. Many sources provide calcium, sulphated, silica-rich waters which are very slightly radioactive at 45° or cold, and finally with bicarbonatees. They, according to their origin and their temperature, are used either for showers or baths, in a swimming-pool, or to drink. These warm waters are especially indicated for degenerative rheumatism such as lumbar or cervical arthritis, osteoarthritis, sciatica, acute lumbago, recurrent arthritis of the hands, knee osteoarthritis, and for inflammatory rheumatism and spontylarthrite rheumatism. The use of sources is also beneficial for the algodystrophy, tendonitis, and phlebological problems (chronic venous insufficiency, suites and sequelae of thrombosis, lymphatic insufficiency, Raynaud's disease), on the other hand, these waters are contraindicated for the varicose ulcer, stroke or recent cardiac events. The cure techniques are the use of showers, individual enclosure (Berthollet), physiotherapy, mud application, underwater showers, and rehabilitation in a swimming pool. By their calming of the nervous system, the waters can cause euphoric relaxation.
The national baths of Aix-les-Bains consist of two buildings located on two very distinct sites. Thus the Thermes Pellegrini and the Thermes Chevalley Spa facilities are located on the height.
Superheated water
The energy required to heat water is significantly lower than that needed to vaporize it, for example for steam distillation
and the energy is easier to recycle using heat exchangers. The energy requirements can be calculated from steam tables. For example, to heat water from 25 °C to steam at 250 °C at 1 atm requires 2869 kJ/kg. To heat water at 25 °C to liquid water at 250 °C at 5 MPa requires only 976 kJ/kg. It is also possible to recover much of the heat (say 75%) from superheated water, and therefore energy use for superheated water extraction is less than one sixth that needed for steam distillation. This also means that the energy contained in superheated water is insufficient to vaporise the water on decompression. In the above example, only 30% of the water would be converted to vapour on decompression from 5 MPa to atmospheric pressure.
Handpresso
The temperature of the water is very important for the final result. If freshly boiled water from a kettle is used, the water temperature is about 203 °F (95 °C) when it gets in contact with the coffee. The water from a thermo flask is usually cooler, but temperatures down to 176 °F (80 °C) still gives an acceptable result with most coffees.
Boiling
Boiling is the rapid vaporization of a liquid, which occurs when a liquid is heated to its boiling point, the temperature at which the vapour pressure of the liquid is equal to the pressure exerted on the liquid by the surrounding atmosphere. There are two main types of boiling: nucleate boiling where small 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. Transition boiling is an intermediate, unstable form of boiling with elements of both types. The boiling point of water is 100 °C or 212 °F but is lower with the decreased atmospheric pressure found at higher altitudes.
Electric water boiler
An electric water boiler, also called a thermo pot, is a consumer electronics small appliance used for boiling water and maintaining it at a constant temperature. It is typically used to provide an immediate source of hot water for making tea, hot chocolate, coffee, instant noodles, or baby formula, or for any other household use where clean hot water is required. They are a common component of Japanese kitchens and the kitchens of many East Asian countries but are found in varying use globally. Some thermo pots are designed with a feature that can purify water.
Vapor
The normal boiling point of a liquid is the temperature at which the vapor pressure is equal to normal atmospheric pressure.
Heat transfer
The boiling point of a substance is the temperature at which the vapor pressure of the liquid equals the pressure surrounding the liquid and the liquid evaporates resulting in an abrupt change in vapor volume.
Pressurized water reactor
Light water is used as the primary coolant in a PWR. Water enters through the bottom of the reactor's core at about and is heated as it flows upwards through the reactor core to a temperature of about . The water remains liquid despite the high temperature due to the high pressure in the primary coolant loop, usually around 155 bar (15.5 MPa 153 atm, 2,250 psi).
In water, the critical point occurs at around and 22.064 MPa (3200 psi or 218 atm).
Temperature
By international agreement the Kelvin and Celsius scales are defined by two fixing points: absolute zero and the triple point of Vienna Standard Mean Ocean Water, which is water specially prepared with a specified blend of hydrogen and oxygen isotopes. Absolute zero is defined as precisely and . It is the temperature at which all classical translational motion of the particles comprising matter ceases and they are at complete rest in the classical model. Quantum-mechanically, however, zero-point motion remains and has an associated energy, the zero-point energy. Matter is in its ground state, and contains no thermal energy. The triple point of water is defined as and . This definition serves the following purposes: it fixes the magnitude of the kelvin as being precisely 1 part in 273.16 parts of the difference between absolute zero and the triple point of water; it establishes that one kelvin has precisely the same magnitude as one degree on the Celsius scale; and it establishes the difference between the null points of these scales as being ( = and = ).
Poaching (cooking)
Water is a relatively efficient conductor of heat, but it also has a fairly low limit to its maximum potential temperature (212 °F (100 °C) at sea level). As such, it is a technique that applies itself to a broad spectrum of methods and results.
It is used to regulate food at a low temperature for extended periods, as with sous-vide. It is also used to rapidly raise the temperature of foods, as with blanching.
Properties of water
The properties of water have historically been used to define various temperature scales. Notably, the Kelvin, Celsius, Rankine, and Fahrenheit scales were, or currently are, defined by the freezing and boiling points of water. The less common scales of Delisle, Newton, Réaumur and Rømer were defined similarly. The triple point of water is a more commonly used standard point today.
Boiler feedwater
Water has higher heat capacity than most other substances. This quality makes it an ideal raw material for boiler operations. Boilers are part of a closed system as compared to open systems in a gas turbine. The closed system that is used is the Rankine cycle. This means that the water is recirculated throughout the system and is never in contact with the atmosphere. The water is reused and needs to be treated to continue efficient operations. Boiler water must be treated in order to be proficient in producing steam. Boiler water is treated to prevent scaling, corrosion, foaming, and priming. Chemicals are put into boiler water through the chemical feed tank to keep the water within chemical range. These chemicals are mostly oxygen scavengers and phosphates. The boiler water also has frequent blowdowns in order to keep the chloride content down. The boiler operations also include bottom blows in order to get rid of solids. Scale is precipitated impurities out of the water and then forms on heat transfer surfaces. This is a problem because scale does not transfer heat very well and causes the tubes to fail by getting too hot. Corrosion is caused by oxygen in the water. The oxygen causes the metal to oxidize which lowers the melting point of the metal. Foaming and priming is caused when the boiler water does not have the correct amount of chemicals and there are suspended solids in the water which carry over in the dry pipe. The dry pipe is where the steam and water mixture are separated.
Rømer scale
In this scale, the zero was initially set using freezing brine. The boiling point of water was defined as 60 degrees. Rømer then saw that the freezing point of pure water was roughly one eighth of the way (about 7.5 degrees) between these two points, so he redefined the lower fixed point to be the freezing point of water at precisely 7.5 degrees. This did not greatly change the scale but made it easier to calibrate by defining it by reference to pure water. Thus the unit of this scale, a Rømer degree, is 100/52.5 = 40/21 of a kelvin or Celsius degree. The symbol is sometimes given as °R, but since that is also sometimes used for the Réaumur and Rankine scales, the other symbol °Rø is to be preferred.
Properties of water
The temperature and pressure at which ordinary solid, liquid, and gaseous water coexist in equilibrium is a triple point of water. Since 1954, this point had been used to define the base unit of temperature, the kelvin but, starting in 2019, the kelvin will be defined using the Boltzmann constant, rather than the triple point of water.
Nucleate boiling
Nucleate boiling is a type of boiling that takes place when the surface temperature is hotter than the saturated fluid temperature by a certain amount but where the heat flux is below the critical heat flux. For water, as shown in the graph below, nucleate boiling occurs when the surface temperature is higher than the saturation temperature (T) by between to . The critical heat flux is the peak on the curve between nucleate boiling and transition boiling. The heat transfer from surface to liquid is greater than that in film boiling.
Celsius
One effect of defining the Celsius scale at the triple point of Vienna Standard Mean Ocean Water (VSMOW, 273.16 K and 0.01 °C), and at absolute zero (0 K and −273.15 °C), is that neither the melting nor boiling point of water under one standard atmosphere (101.325 kPa) remains a defining point for the Celsius scale. In 1948 when the 9th General Conference on Weights and Measures (CGPM) in Resolution 3 first considered using the triple point of water as a defining point, the triple point was so close to being 0.01 °C greater than water's known melting point, it was simply defined as precisely 0.01 °C. However, current measurements show that the difference between the triple and melting points of VSMOW is actually very slightly (<0.001 °C) greater than 0.01 °C. Thus, the actual melting point of ice is very slightly (less than a thousandth of a degree) below 0 °C. Also, defining water's triple point at 273.16 K precisely defined the magnitude of each 1 °C increment in terms of the absolute thermodynamic temperature scale (referencing absolute zero). Now decoupled from the actual boiling point of water, the value "100 °C" is hotter than 0 °C – in absolute terms – by a factor of "precisely" (approximately 36.61% thermodynamically hotter). When adhering "strictly" to the two-point definition for calibration, the boiling point of VSMOW under one standard atmosphere of pressure is actually 373.1339 K (99.9839 °C). When calibrated to ITS-90 (a calibration standard comprising many definition points and commonly used for high-precision instrumentation), the boiling point of VSMOW is slightly less, about 99.974 °C.
Bain-marie
When the working fluid is water and the bain-marie is used at sea level, the maximum temperature of the material in the lower container will not exceed 100 degrees Celsius (212 °F), the boiling point of water at sea level. Using different working fluids, for example, oil, in the lower container will result in different maximum temperatures.
Vapor pressure
Like all liquids, water boils when its vapor pressure reaches its surrounding pressure. In nature, the atmospheric pressure is lower at higher elevations and water boils at a lower temperature. The boiling temperature of water for atmospheric pressures can be approximated by the Antoine equation:
Eriksdalsbadet
The water temperature is usually 27 degrees Celsius.
Hydrogen production
Water spontaneously dissociates at around 2500 °C, but this thermolysis occurs at temperatures too high for usual process piping and equipment. Catalysts are required to reduce the dissociation temperature.
Coffee extraction
Water temperature is subtler but crucial to the proper extraction of flavor from the ground coffee, as it affects the proportions in which solubles are extracted – one wishes to extract the desired flavors as much as possible, and the undesirable flavors as little as possible. The recommended brewing temperature range of coffee is 91–94 °C (195–202 °F), which is a trade-off between these goals. If cooler, some of the solubles that make up the flavor will not be extracted. If the water is too hot, some undesirable, bitter, elements will be extracted, adversely affecting the taste. Note that this desired temperature range is slightly below the boiling point of water (100 °C or 212 °F at standard pressure), so coffee is best made with water that has been allowed to come off the boil slightly. Another consideration is the difference between the temperature of the water and the temperature of the coffee slurry: for example, certain brewing methods (e.g., manual pourover) can result in losing a significant amount of heat to the atmosphere during the brewing process.
Frying Pan Lake
The water of Frying Pan Lake is typically steaming and can appear to be boiling due to carbon dioxide and hydrogen sulphide gas bubbling to the surface, however, the lake's average temperature is . The lake and its outflow, Waimangu Stream (referred to as Hot Water Creek in the Waimangu Wanderer Guide), have an average pH level of 3.8, even though some of the boiling hot springs and vents on the lake's bed feed it with alkaline water of pH 8.2 to 8.7. This leads to various gradients of pH levels, which govern which types of algae are present, the blue-green algae "Mastigocladus laminosus", or the eukaryotic algae "Cyanidium caldarium".
Summer Lake Hot Springs
In 1937, the Geological Survey measured the main spring’s temperature at with a flow of per minute. In 1948, the Geological Survey re-measured the flow at per minute. A more detailed measurement in 1978 found the reservoir temperature below the springs varied between and with an average reservoir temperature of 118. The average surface temperature of the springs was with discharge of per minute. In 2012, the Oregon Department of Geology and Mineral Industries reported that the hot springs’ temperature was with a water flow of per minute. At the release point in the main pool of the Summer Lake Hot Springs bathhouse, the water temperature is approximately . The three other hot springs produce water temperatures between and at their release points.
Daniel Gabriel Fahrenheit
Fahrenheit came up with the idea that Mercury boils around 300 degrees on this temperature scale. Work by others showed that water boils about 180 degrees above its freezing point. The Fahrenheit scale later was redefined to make the freezing-to-boiling interval exactly 180 degrees, a convenient value as 180 is a highly composite number, meaning that it is evenly divisible into many fractions. It is because of the scale's redefinition that normal body temperature today is taken as 98.6 degrees, whereas it was 96 degrees on Fahrenheit's original scale.
Water
The hydrogen bonds are also the reason why the melting and boiling points of water are much higher than those of other analogous compounds like hydrogen sulfide (). They also explain its exceptionally high specific heat capacity (about 4.2 J/g/K), heat of fusion (about 333 J/g), heat of vaporization (), and thermal conductivity (between 0.561 and 0.679 W/m/K). These properties make water more effective at moderating Earth's climate, by storing heat and transporting it between the oceans and the atmosphere. The hydrogen bonds of water are of moderate strength, around 23 kJ/mol (compared to a covalent O-H bond at 492 kJ/mol). Of this, it is estimated that 90% of the hydrogen bond is attributable to electrostatics, while the remaining 10% reflects partial covalent character.
Vienna Standard Mean Ocean Water
This boiling–point difference of 16.1 millikelvins between the Celsius scale's original definition and the current one (based on absolute zero and the triple point) has little practical meaning in real life because water's boiling point is highly sensitive to variations in barometric pressure. For example, an altitude change of only 28 cm (11 in) causes water's boiling point to change by one millikelvin.
Siamese fighting fish
"Betta" species prefer a water temperature of around but have been seen to survive temporarily at the extremes of or . When kept in colder climates, aquarium heaters are recommended.
Subcooling
The term subcooling also called undercooling refers to a liquid existing at a temperature below its normal boiling point. For example, water boils at 373 K; at room temperature (300 K) the water is termed "subcooled". A subcooled liquid is the convenient state in which, say, refrigerants may undergo the remaining stages of a refrigeration cycle. Normally, a refrigeration system has a subcooling stage, allowing technicians to be certain that the quality, in which the refrigerant reaches the next step on the cycle, is the desired one. Subcooling may take place in heat exchangers and outside them. Being both similar and inverse processes, subcooling and superheating are important to determine stability and well-functioning of a refrigeration system.
Plitvice Lakes National Park
The water temperature at the springs is usually below 10 °C (50 °F). Within the rivers and lakes, the water temperature rises up to 20 °C (68 °F). The following example for different water temperatures measured on July 7, 1954 demonstrates large temperature differences within the lakes: Within lake Kozjak at the depth of 4 m a temperature of 18.9 °C (66 °F) has been measured. At a depth of 20 m, 5 °C (41 °F) have been measured. At 44 m depth, virtually at the bottom of the lake, a temperature of 4.1 °C (39 °F) has been measured.
Multi-stage flash distillation
When the plant is operating in steady state, feed water at the cold inlet temperature flows, or is pumped, through the heat exchangers in the stages and warms up. When it reaches the brine heater it already has nearly the maximum temperature. In the heater, an amount of additional heat is added. After the heater, the water flows through valves back into the stages that have ever lower pressure and temperature. As it flows back through the stages the water is now called brine, to distinguish it from the inlet water. In each stage, as the brine enters, its temperature is above the boiling point at the pressure of the stage, and a small fraction of the brine water boils ("flashes") to steam thereby reducing the temperature until an equilibrium is reached. The resulting steam is a little hotter than the feed water in the heat exchanger. The steam cools and condenses against the heat exchanger tubes, thereby heating the feed water as described earlier.
The total evaporation in all the stages is up to approximately 15% of the water flowing through the system, depending on the range of temperatures used. With increasing temperature there are growing difficulties of scale formation and corrosion. 120 °C appears to be a maximum, although scale avoidance may require temperatures below 70 °C.
List of Dutch inventions and innovations
Various authors have credited the invention of the thermometer to Cornelis Drebbel, Robert Fludd, Galileo Galilei or Santorio Santorio. The thermometer was not a single invention, however, but a development. However, each inventor and each thermometer was unique – there was no standard scale. In 1665 Christiaan Huygens suggested using the melting and boiling points of water as standards. The Fahrenheit scale is now usually defined by two fixed points: the temperature at which water freezes into ice is defined as 32 degrees Fahrenheit (°F), and the boiling point of water is defined to be 212 °F, a 180 degree separation, as defined at sea level and standard atmospheric pressure. In 1742, Swedish astronomer Anders Celsius created a temperature scale which was the reverse of the scale now known by the name "Celsius": "0" represented the boiling point of water, while "100" represented the freezing point of water. From 1744 until 1954, 0 °C was defined as the freezing point of water and 100 °C was defined as the boiling point of water, both at a pressure of one standard atmosphere with mercury being the working material.
Aquastat
An aquastat is a device used in hydronic heating systems for controlling water temperature. To prevent the boiler from firing too often, aquastats have a high limit temperature and a low limit. If the thermostat is calling for heat, the boiler will fire until the high limit is reached, then shut off (even if the thermostat is still calling for heat). The boiler will re-fire if the boiler water temperature drops below a range around the high limit. The high limit exists for the sake of efficiency and safety. The boiler will also fire (regardless of thermostat state) when the boiler water temperature goes below a range around the low limit, ensuring that the boiler water temperature remains above a certain point. The low limit is intended for tankless domestic hot water---it ensures that boiler water is always warm enough to heat the domestic hot water. Many aquastats also have a differential ("diff") control which determines the size of the range around the "low" and/or "high" controls.
Water heating
Two conflicting safety issues affect water heater temperature—the risk of scalding from excessively hot water greater than , and the risk of incubating bacteria colonies, particularly "Legionella", in water that is not hot enough to kill them. Both risks are potentially life-threatening and are balanced by setting the water heater's thermostat to . The European Guidelines for Control and Prevention of Travel Associated Legionnaires’ Disease recommend that hot water should be stored at and distributed so that a temperature of at least and preferably is achieved within one minute at points of use.
Thermodynamic temperature
so that
Armstrong limit
At the nominal body temperature of 37 °C (98.6 °F), water has a vapour pressure of ; which is to say, at an ambient pressure of , the boiling point of water is 37 °C (98.6 °F). A pressure of 6.3 kPa—the Armstrong limit—is about 1/16 of the standard sea-level atmospheric pressure of . Modern formulas for calculating the standard pressure at a given altitude vary—as do the precise pressures one will actually measure at a given altitude on a given day—but a common formula shows that 6.3 kPa is typically found at an altitude of .
Newton scale
Newton used linseed oil as thermometric material and measured its change of volume against his reference points. He set as 0 on his scale "the heat of air in winter at which water begins to freeze" ("Calor aeris hyberni ubi aqua incipit gelu rigescere"), reminiscent of the standard of the modern Celsius scale (i.e. 0 °N = 0 °C), but he has no single second reference point; he does give the "heat at which water begins to boil" as 33, but this is not a defining reference; the values for body temperature and the freezing and boiling point of water suggest a conversion factor between the Newton and the Celsius scale of between about 3.08 (12 °N = 37 °C) and 3.03 (33 °N = 100 °C) but since the objectively verifiable reference points given result in irreconcilable data (especially for high temperatures), no unambiguous "conversion" between the scales is possible.
Laboratory water bath
A water bath is laboratory equipment made from a container filled with heated water. It is used to incubate samples in water at a constant temperature over a long period of time. All water baths have a digital or an analogue interface to allow users to set a desired temperature. Utilisations include warming of reagents, melting of substrates or incubation of cell cultures. It is also used to enable certain chemical reactions to occur at high temperature. Water bath is a preferred heat source for heating flammable chemicals instead of an open flame to prevent ignition. Different types of water baths are used depending on application. For all water baths, it can be used up to 99.9 °C. When temperature is above 100 °C, alternative methods such as oil bath, silicone bath or sand bath may be used.Circulating the 
water baths (also called "stirrers" ")" are ideal for applications when temperature uniformity and consistency are critical, such as enzymatic and serologic experiments. Water is thoroughly circulated throughout the bath resulting in a more uniform temperature.
Fahrenheit
Fahrenheit observed that water boils at about 212 degrees using this scale. The use of the freezing and boiling points of water as thermometer fixed reference points became popular following the work of Anders Celsius and these fixed points were adopted by a committee of the Royal Society led by Henry Cavendish in 1776. Under this system, the Fahrenheit scale is redefined slightly so that the freezing point of water is exactly 32 °F, and the boiling point is exactly 212 °F or 180 degrees higher. It is for this reason that normal human body temperature is approximately 98° (oral temperature) on the revised scale (whereas it was 90° on Fahrenheit's multiplication of Rømer, and 96° on his original scale).
Waterside hot water hay pellet furnace
The temperature in the water chamber of the furnace can reach the boiling point within seven minutes and at that rate the furnace can burn off the majority of the ash and leave little waste.
Once development was complete on the furnace the final working prototype of the Waterside Hay Hot Water Pellet Furnace was 45 inches tall and around a foot in diameter. It can burn 50 – 125 pounds of pellets a day and releases 30,000 – 190,000 BTU's (British thermal units) an hour.
Heat
There are important exceptions. They break the obviously apparent link between heat and temperature. They make it clear that empirical definitions of temperature are contingent on the peculiar properties of particular thermometric substances, and are thus precluded from the title 'absolute'. For example, water contracts on being heated near 277 K. It cannot be used as a thermometric substance near that temperature. Also, over a certain temperature range, ice contracts on heating. Moreover, many substances can exist in metastable states, such as with negative pressure, that survive only transiently and in very special conditions. Such facts, sometimes called 'anomalous', are some of the reasons for the thermodynamic definition of absolute temperature.
Bert Bolle Barometer
Visitors could walk up the stairs and take a reading in the Reading Room atop the Tower.
At the moment when the water reached its highest possible point in the glass pipe, visitors could witness an interesting physical phenomenon for about a minute. The air pressure above the water had lowered dramatically. Therefore, the evaporation of the water happened so vigorously that the water started to boil spontaneously, although its temperature rarely exceeded 20 °C. This ‘cold boiling’ is contributed to by air bubbles that were formed in the water column. 
As soon as the pump was disconnected, the evacuating of the pipe stopped and the water level became calm again, enabling people to take a reading. During the time the water level was calm, there was still some turbulence at the surface due to air bubbles rising to the top of the apparatus. 
Although water vapour pressure depressed the barometers pressure reading, visitors were told how to correct for this error and thus calculate the real air pressure, and could then compare it with the accurate Vaisala digital standard barometer in the Tower.
After a reading period of two minutes, air was gradually admitted to the vacuum in the top area of the pipe. Within another two minutes all the water had returned to the reservoir downstairs, after which the six-minute pump cycle of the Bert Bolle Barometer repeated.
Vienna Standard Mean Ocean Water
One effect of defining the triple point of VSMOW as both 0.01 °C and 273.16 K is that neither the melting or boiling point of water under one standard atmosphere (101.325 kPa) remain defining points for the Celsius scale. In 1948, when the 9th General Conference on Weights and Measures (CGPM) in Resolution 3 first considered using the triple point of water as a defining point, the triple point was so close to being 0.01 °C greater than water's known melting point, it was simply defined as exactly 0.01 °C. However, current measurements show that the triple and melting points of VSMOW water are only  °C apart. Thus, the actual melting point of ice is  °C. Also, defining water's triple point at 273.16 K defined the magnitude of each 1 °C increment in terms of the absolute thermodynamic temperature scale (referencing absolute zero). Now decoupled from the actual boiling point of water, the value "100 °C" is hotter than 0 °C, in absolute terms, by a factor of "exactly" formula_1 (approximately 36.61% thermodynamically hotter). When adhering "strictly" to the two-point definition for calibration, the boiling point of VSMOW water under one standard atmosphere of pressure is actually 373.1339 K (99.9839 °C). When calibrated to ITS-90 (a calibration standard comprising many definition points and commonly used for high-precision instrumentation), the boiling point of VSMOW water is slightly less, about 99.974 °C.
Atmospheric pressure
Pure water boils at at earth's standard atmospheric pressure. The boiling point is the temperature at which the vapor pressure is equal to the atmospheric pressure around the water. Because of this, the boiling point of water is lower at lower pressure and higher at higher pressure. Cooking at high elevations, therefore, requires adjustments to recipes or pressure cooking. A rough approximation of elevation can be obtained by measuring the temperature at which water boils; in the mid-19th century, this method was used by explorers.
Hot water storage tank
Hot water can cause painful, dangerous scalding injuries, especially in children and the elderly. Water at the outlet should not exceed 49 degrees Celsius. Some jurisdictions set a limit of 49 degrees on tank setpoint temperature. On the other hand, water stored below 60 degrees Celsius can permit the growth of bacteria, such as those that cause Legionnaire's disease, which is a particular danger to those with compromised immune systems. One technical solution would be use of mixing valves at outlets used for sinks, baths or showers, that would automatically mix cold water to maintain a maximum below 49 C. A proposal to add this to the building code of Canada was unsuccessful.
Boiling water reactor safety systems
At "T"+40, core temperature is at and rising steadily; CS and LPCI kick in and begins deluging the steam above the core, and then the core itself. First, a large amount of steam still trapped above and within the core has to be knocked down first, or the water will be flashed to steam prior to it hitting the rods. This happens after a few seconds, as the approximately 200,000 L/min (3,300 L/s, 52,500 US gal/min, 875 US gal/s) of water these systems release begin to cool first the top of the core, with LPCI deluging the fuel rods, and CS suppressing the generated steam until at approximately "T"+100 seconds, all of the fuel is now subject to deluge and the last remaining hot-spots at the bottom of the core are now being cooled. The peak temperature that was attained was (well below the maximum of established by the NRC) at the bottom of the core, which was the last hot spot to be affected by the water deluge.
Boiling point (disambiguation)
The boiling point of a substance is the temperature at which it can change its state from a liquid to a gas.
Yuwaku Onsen
The hot spring is at an altitude of 400 meters above sea level at the foot of Mount Ioh. The water is slightly alkaline and contains gypsum. The mean temperature for the water is 32°C.
Pseudoscientific metrology
More recently Butler and Knight claimed that, on a scale where the absolute zero is defined as being minus 1,000 degrees, water boils at the temperature of 366 degrees, an "utterly remarkable" result according to the authors, which they believe points at something intrinsically fundamental in these numbers.
Bath, Somerset
Water bubbling up from the ground as geothermal springs originates as rain on the Mendip Hills. The rain percolates through limestone aquifers to a depth of between where geothermal energy raises the water's temperature to between 64 and 96 °C (approximately 147–205 °F). Under pressure, the heated water rises to the surface along fissures and faults in the limestone. Hot water at a temperature of rises here at the rate of daily, from a geological fault (the Pennyquick fault). In 1983, a new spa-water bore-hole was sunk, providing a clean and safe supply for drinking in the Pump Room. There is no universal definition to distinguish a hot spring from a geothermal spring although, by several definitions, the Bath springs can be considered the only hot springs in the UK. Three of the springs feed the thermal baths.
Wulai Hot Spring
The water of the hot spring is clear and odorless with a temperature up to 80°C.
Kochbrunnen
The Kochbrunnen (in German: boil fountain) in Wiesbaden is the most famous hot spring in city. It is a sodium chloride hot spring. Its name refers to the water temperature of about 66 °C.
Compounds of fluorine
Hydrogen bonding amongst HF molecules gives rise to high viscosity in the liquid phase and lower than expected pressure in the gas phase. Hydrogen fluoride does not boil until 20 °C in contrast to the heavier hydrogen halides which boil between −85 °C and −35 °C (−120 °F and –30 °F). HF is fully miscible with water (will dissolve in any proportion), while the other hydrogen halides have large solubility gaps with water. Hydrogen fluoride and water also form several compounds in the solid state, most notably a 1:1 compound that does not melt until −40 °C (−40 °F), which is 44 degrees Celsius (79 degrees Fahrenheit) above the melting point of pure HF.
Boiler (water heating)
The boiler heats water to a temperature controlled by a thermostat. The water then flows (either by natural circulation or by a pump) to radiators in the rooms which are to be heated. Water also flows through a coil in the hot water tank to heat a separate mass of water for bathing, etc.
Pikes Peak
At the peak, the partial pressure of oxygen is only about 60% of that at sea level. Water boils at at 14,000 feet, rather than at sea level.
Superheating
Water is said to "boil" when bubbles of water vapor grow without bound, bursting at the surface. For a vapor bubble to expand, the temperature must be high enough that the vapor pressure exceeds the ambient pressure (the atmospheric pressure, primarily). Below that temperature, a water vapor bubble will shrink and vanish.
International Temperature Scale of 1990
There are often small differences between measurements calibrated per ITS–90 and thermodynamic temperature. For instance, precise measurements show that the boiling point of VSMOW water under one standard atmosphere of pressure is actually 373.1339 K (99.9839 °C) when adhering "strictly" to the two-point definition of thermodynamic temperature. When calibrated to ITS–90, where one must interpolate between the defining points of gallium and indium, the boiling point of VSMOW water is about 10 mK less, about 99.974 °C. The virtue of ITS–90 is that another lab in another part of the world will measure the very same temperature with ease due to the advantages of a comprehensive international calibration standard featuring many conveniently spaced, reproducible, defining points spanning a wide range of temperatures.
Heat
where by definition
United States customary units
The relationship between the different temperature scales is linear but the scales have different zero points, so conversion is not simply multiplication by a factor. Pure water freezes at 32 °F = 0 °C and boils at 212 °F = 100 °C at 1 atm. The conversion formula is:
Fahrenheit
According to a letter Fahrenheit wrote to his friend Herman Boerhaave, his scale was built on the work of Ole Rømer, whom he had met earlier. In Rømer's scale, brine freezes at zero, water freezes and melts at 7.5 degrees, body temperature is 22.5, and water boils at 60 degrees. Fahrenheit multiplied each value by four in order to eliminate fractions and make the scale more fine-grained. He then re-calibrated his scale using the melting point of ice and normal human body temperature (which were at 30 and 90 degrees); he adjusted the scale so that the melting point of ice would be 32 degrees and body temperature 96 degrees, so that 64 intervals would separate the two, allowing him to mark degree lines on his instruments by simply bisecting the interval six times (since 64 is 2 to the sixth power).
Electric water boiler
Black tea is typically steeped at 
while green tea is steeped at under . A number of thermo pot models offer an adjustable target temperature.
Superheated water
Self-ionization of water increases with temperature, and the pKw of water at 250 °C is closer to 11 than the more familiar 14 at 25 °C. This means the concentration of hydronium ion () and the concentration of hydroxide () are increased while the pH remains neutral. Specific heat capacity at constant pressure also increases with temperature, from 4.187 kJ/kg at 25 °C to 8.138 kJ/kg at 350 °C. A significant effect on the behaviour of water at high temperatures is decreased dielectric constant (relative permittivity).
Boiling point
The element with the lowest boiling point is helium. Both the boiling points of rhenium and tungsten exceed 5000 K at standard pressure; because it is difficult to measure extreme temperatures precisely without bias, both have been cited in the literature as having the higher boiling point.
Celsius
This boiling-point difference of 16.1 millikelvins between the Celsius scale's original definition and the current one (based on absolute zero and the triple point) has little practical meaning in common daily applications because water's boiling point is very sensitive to variations in barometric pressure. For example, an altitude change of only 28 cm (11 in) causes the boiling point to change by one millikelvin.
Pot still
The liquid being distilled is a mixture of mainly water and alcohol, along with smaller amounts of other by-products of fermentation (called congeners), such as aldehydes and esters. Alcohol (ethanol) has a normal boiling point of 78.4 °C (173.12 °F), compared with pure water, which boils at 100 °C (212 °F). As alcohol has a lower boiling point, it is more volatile and evaporates at a higher rate than water. Therefore, the concentration of alcohol in the vapour phase above the liquid is higher than in the liquid itself.
High-altitude cooking
At sea level, water boils at . For every increase in elevation, water's boiling point is lowered by approximately 0.5 °C. At in elevation, water boils at just . Boiling as a cooking method must be adjusted or alternatives applied. Vegetables and some starches will simply take longer to cook, while rice and legumes (beans) usually require a pressure cooker. Pasta will also require a pressure cooker.
Water heating
Domestically, water is traditionally heated in vessels known as "water heaters", "kettles", "cauldrons", "pots", or "coppers". These metal vessels that heat a batch of water do not produce a continual supply of heated water at a preset temperature. Rarely, hot water occurs naturally, usually from natural hot springs. The temperature varies with the consumption rate, becoming cooler as flow increases.
Azeotrope
In general, a negative azeotrope boils at a higher temperature than any other ratio of its constituents. Negative azeotropes are also called "maximum boiling mixtures" or "pressure minimum" azeotropes. An example of a negative azeotrope is hydrochloric acid at a concentration of 20.2% and 79.8% water (by mass). Hydrogen chloride boils at −84 °C and water at 100 °C, but the azeotrope boils at 110 °C, which is higher than either of its constituents. The maximum temperature at which any hydrochloric acid solution can boil is 110 °C. Other examples:
Critical point (thermodynamics)
In water, the critical point occurs at around 647 K (374 °C or 705 °F) and 22.064 MPa (3200 psia or 218 atm).
Ebullism
In 1960, Joseph Kittinger experienced localised ebullism during a ascent in a helium-driven gondola. His right-hand glove failed to pressurise and his hand expanded to roughly twice its normal volume accompanied by disabling pain. His hand took about 3 hours to recover after his return to the ground.
In the atmospheric pressure present at sea level, water boils at . At an altitude of , it boils at only , the normal body temperature of humans. This altitude is known as "Armstrong’s Line." In practice bodily fluids do not boil off at this altitude. This is because the skin and outer organs have enough strength to withstand this pressure, thus pressure inside the body would be significantly higher—however, bubbles starting to form is still an issue.
Thermodynamic temperature
By international agreement, the unit "kelvin" and its scale are defined by two points: absolute zero, and the triple point of Vienna Standard Mean Ocean Water (water with a specified blend of hydrogen and oxygen isotopes). Absolute zero, the lowest possible temperature, is defined as being precisely 0 K "and" −273.15 °C. The triple point of water is defined as being precisely 273.16 K "and" 0.01 °C. This definition does three things:
Water (data page)
For temperature range: 173.15 K to 273.15 K or equivalently −100 °C to 0 °C
Takhini Hot Springs
According to tests, it has taken a minimum of 60 years for the water in the pools to come from the ground into the source. During its underground journey to the surface, the water reaches a maximum temperature of 95° Celsius (203° Fahrenheit) and then cools down as it rises to the surface and into the source.
Vapor
"Vapor" refers to a gas phase at a temperature where the same substance can also exist in the liquid or solid state, below the critical temperature of the substance. (For example, water has a critical temperature of 374 °C (647 K), which is the highest temperature at which liquid water can exist.) If the vapor is in contact with a liquid or solid phase, the two phases will be in a state of equilibrium. The term "gas" refers to a compressible fluid phase. Fixed gases are gases for which no liquid or solid can form at the temperature of the gas, such as air at typical ambient temperatures. A liquid or solid does not have to boil to release a vapor.
Temperature
The United States commonly uses the Fahrenheit scale, on which water freezes at and boils at at sea-level atmospheric pressure.
Borjomi (water)
Borjomi is a water of volcanic origin which is over 1,500 years old. It is pushed up to the surface from 1500m below ground by natural carbon dioxide pressure. Borjomi does not cool down before it reaches the surface and comes out at a temperature of . The Borjomi springs are located in the central part of the Adjara-Imereti mountain range of Greater Caucasus at an altitude of above sea level. The average depth of each of the nine spring wells is .
Vapor
For example, water has a critical temperature of , which is the highest temperature at which liquid water can exist. In the atmosphere at ordinary temperatures, therefore, gaseous water (known as water vapor) will condense into a liquid if its partial pressure is increased sufficiently.
Water heating
Water typically enters residences in the US at about , depending on latitude and season. Hot water temperatures of are usual for dish-washing, laundry and showering, which requires that the heater raise the water temperature about if the hot water is mixed with cold water at the point of use. The Uniform Plumbing Code reference shower flow rate is per minute. Sink and dishwasher usages range from per minute.
Boiling
Evaporation only happens on the surface while boiling happens throughout the liquid.
When a liquid reaches its boiling point bubbles of gas form in it which rise into the surface and burst into the air. This process is called boiling. If the boiling liquid is heated more strongly the temperature does not rise but the liquid boils more quickly.
Thermal Battery
Phase change materials used for thermal storage are capable of storing and releasing significant thermal capacity at the temperature that they change phase. These materials are chosen based on specific applications because there is a wide range of temperatures that may be useful in different applications and a wide range of materials that change phase at different temperatures. These materials include salts and waxes that are specifically engineered for the applications they serve. In addition to manufactured materials, water is a phase change material. The latent heat of water is 334 joules/gram. The phase change of water occurs at 0°C (32°F).
Thermostatic mixing valve
It is increasingly common practice around the world to regulate the storage water temperature to above 60 °C (140 °F), and to circulate or distribute water at a temperature less than 50 °C (122 °F). Water above these temperatures can cause scald injuries. Many countries, states, or municipalities now require that the temperature of all bath water in newly built and extensively refurbished domestic properties be controlled to a maximum of 48 °C (118 °F). Installing thermostatic mixing valves can ensure that water is delivered at the required temperature, thereby reducing the risk of scalding accidents; it also reduces hot water consumption from a supply that is maintained at a higher temperature.
Yuseong Foot Spa
According to the signboard beside the foot spa, the spring’s waters originate between 215 and 450 meters deep and have various minerals. The water temperature is variable and rather high, ranging from a steamy 41 degrees to a blazing 57 degrees Celsius.