Blackboard bold: Difference between revisions

From formulasearchengine
Jump to navigation Jump to search
en>ZéroBot
m r2.7.1) (Robot: Adding ja:黒板太字
 
en>Epicgenius
Undid revision 592178586 by Epicgenius (talk)
Line 1: Line 1:
{{for2|the physical processes that takes place at the melting point|[[Melting]], [[Freezing]] and [[Crystallization]]}}


The '''melting point''' (or, rarely, '''liquefaction point''') of a solid is the temperature at which it changes [[states of matter|state]] from [[solid]] to [[liquid]] at atmospheric pressure. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends (usually slightly) on pressure and is usually specified at [[Standard conditions for temperature and pressure|standard]] pressure. When considered as the temperature of the reverse change from liquid to solid, it is referred to as the '''freezing point''' or '''crystallization point'''. Because of the ability of some substances to [[supercool]], the freezing point is not considered as a characteristic property of a substance. When the "characteristic freezing point" of a substance is determined, in fact the actual methodology is almost always "the principle of observing the disappearance rather than the formation of ice", that is, the [[#Melting point measurements|melting point]].<ref>{{cite journal |url= http://jeb.biologists.org/cgi/reprint/26/1/57.pdf |title= A new method of freezing-point determination for small quantities |author= Ramsay, J. A. |journal= [[J. Exp. Biol.]] |year= 1949 |volume= 26 |issue= 1 |pages= 57–64 |pmid= 15406812}}</ref>


Having honours that vary from "Best Brand new Sneakers Model" so that you can "Charity Event of the 12 months" UGG Modern australia, inventors from the wildly popular Ugg boot truly are a exact company accomplishment report. Founded in 1978 by the Hawaiian customer which replanted him self to be in a position to Los angeles, Uggs had been previously a brand this offered cozy sneakers. For 25 a lot of several years, Uggs chugged coupled creating moderate yet continual income. All over 1994, the firm bought a key phase up a further route. This corporation, underneath the information of the absolutely new business enterprise manager, Decker Backyard Organization, designed organizing switch as effectively as located on its individual to be a brewer about substantial-close luxurious boots or sneakers. All-around 1997, your UGG sneakers established contained a few of shoes or boots, several slipper variants and some daily sneakers sorts. The new positioning like a significant-finish luxurious as well as significant vogue sneakers or boots provider come to be the fantastic match for Uggs Sydney. Inside three years, the fishing line had been regularly remaining displayed inside of designer newspapers and also pictures limbs. The firm developed any suitable connections collectively with Nordstrom as well as the corporation genuinely eradicated. As significant as the new positioning finished up being to UGG's accomplishment, there have been an additional factor that rocketed Uggs Australia's boots collection so that you can all over the world size. During the 12 months The 12 months 2000, only 2 yrs once the organizing rethinking connected with Ugg sheepskin boots Australia's generation, Oprah Winfrey gotten a set of Ugg boots. The specific charming telly coordinator in addition to globally star cherished the boots a fantastic offer of that they purchased 3 hundred fifty frames as presents whole workers members. The lady as well showcased your Ugg sheepskin boots Tremendous Kick out for my little one nicely-regarded Oprah's Favorite Things show. A response was electrical. The specific Ugg sheepskin boots producer obtained turned up. When Oprah highlighted a different Ugg Bailey Button Triplet footwear in her 2003 Oprah's Favourite Elements screen, the tiny a single Pink plus Light-weight blue Uggs Basic Sneakers or boots coming from Ugg boot grew to turn into a runaway family vacation bestseller. That yr has also been 4 seasons in which Ugg sheepskin boots Australia's collection was branded Footwear or boots News' Design of 12 months. These functions wasn't the completed connected with Oprah's connection utilizing the footwear selection, although. Those terrific tv range showcased UGG's Uptown Begin in her possess August 2005 Beloved Problems show, and purchasers on the elaborate footwear vogue skyrocketed in a single day. In just ten years given that switching from 'comfortable shoes' so that you can 'the final in shoes or boots luxury', Uggs in to a significant-fashion decide on, alongside with designed a complete wholly new sounding fashion footwear or boots. Ugg Boots canada and shoes and styles tend to be routinely noticed all more than the world upon designer runways. Uggs Modern australia has not had sexual intercourse in it is laurels, even though. With August 2005, this company thought we would send out a range of it is really basically luck by way of championing a major guide to. The business joined owning Saint. Jude's Your kid's Examine Healthcare facility within a charitable organization event how they intelligently branded Fantastic art in addition to Most important. Ugg boot Estimates questioned made a decision on seen painters, men and women in politics and also celebs handy pattern some of Standard Boot styles. Your finished bags are marketed out of with the ebay affiliate network, along with the dollars handed on in get to E. Jude's. With 2005, the presentation improved by in surplus<br><br>If you have any kind of questions pertaining to where and exactly how to utilize [http://tinyurl.com/m2okfad cheap ugg Australia], you can call us at our web site.
==Examples==
[[File:Carboxylic.Acids.Melting.&.Boiling.Points.jpg|thumb|right|Melting points (in blue) and boiling points (in pink) of the first eight [[carboxylic acids]] (°C)]]For most substances, [[melting]] and [[freezing]] points are approximately equal. For example, the melting point ''and'' freezing point of [[mercury (element)|mercury]] is 234.32 [[kelvin]] (−38.83&nbsp;[[Celsius|°C]] or −37.89&nbsp;[[Fahrenheit|°F]]).<ref>[[#Haynes|Haynes]], p. 4.122.</ref> However, certain substances possess differing solid-liquid transition temperatures. For example, [[agar]] melts at 85&nbsp;°C (185&nbsp;°F) and solidifies from 31&nbsp;°C to 40&nbsp;°C (89.6&nbsp;°F to 104&nbsp;°F); such direction dependence is known as [[hysteresis]].
 
The melting point of [[ice]] at 1 atmosphere of pressure is very close <ref>The melting point of purified water has been measured as 0.002519 ± 0.000002 °C, see {{cite journal|author = Feistel, R. and Wagner, W. |year = 2006
|title = A New Equation of State for H<sub>2</sub>O Ice Ih
|journal = J. Phys. Chem. Ref. Data|volume = 35|issue = 2
|pages = 1021–1047
|doi = 10.1063/1.2183324|bibcode = 2006JPCRD..35.1021F }}
</ref> to 0&nbsp;°C (32&nbsp;°F, 273.15&nbsp;K); this is also known as the '''ice point'''. In the presence of [[Nucleation|nucleating substances]] the freezing point of water is the same as the melting point, but in the absence of nucleators water can [[Supercooling|supercool]] to −42&nbsp;°C (−43.6&nbsp;°F, 231&nbsp;K) before freezing.
 
The [[chemical element]] with the highest melting point is [[tungsten]], at 3687 K (3414 °C, 6177 °F)<ref>[[#Haynes|Haynes]], p. 4.123.</ref> making it excellent for use as filaments in light bulbs. The often-cited [[carbon]] does not melt at ambient pressure but [[sublimation (physics)|sublimes]] at about 4000&nbsp;K; a liquid phase only exists above pressures of 10&nbsp;[[Pascal (unit)|MPa]] and estimated 4300–4700&nbsp;K (see [[:File:Carbon basic phase diagram.png|Carbon phase diagram]]). [[Tantalum hafnium carbide]] (Ta<sub>4</sub>HfC<sub>5</sub>) is a [[refractory]] compound with a very high melting point of 4488&nbsp;K (4215&nbsp;°C, 7619&nbsp;°F).<ref>{{cite journal|title=Researches on Systems with Carbides at High Melting Point and Contributions to the Problem of Carbon Fusion|journal=Z. Tech. Physik|author=Agte, C., and Alterthum, H.| volume= 11|year= 1930|pages=182–191}}</ref> At the other end of the scale, [[helium]] does not freeze at all at normal pressure, even at temperatures very close to [[absolute zero]]; pressures over 20 times normal atmospheric pressure are necessary.
 
==Melting point measurements==
{{main|Melting point apparatus}}
[[File:Koflerbank.jpg|thumb|Kofler bench with samples for calibration]]
Many [[laboratory techniques]] exist for the determination of melting points.
A [[Kofler bench]] is a metal strip with a temperature gradient (range from room temperature to 300 °C). Any substance can be placed on a section of the strip revealing its thermal behaviour at the temperature at that point. [[Differential scanning calorimetry]] gives information on melting point together with its [[enthalpy of fusion]].
 
[[File:KruessM5k.jpg|thumb|Automatic digital melting point meter]]
A basic melting point apparatus for the analysis of crystalline solids consists of an [[oil bath]] with a transparent window (most basic design: a [[Thiele tube]]) and a simple magnifier. The several grains of a solid are placed in a thin glass tube and partially immersed in the oil bath. The oil bath is heated (and stirred) and with the aid of the magnifier (and external light source) melting of the individual crystals at a certain temperature can be observed. In large/small devices, the sample is placed in a heating block, and optical detection is automated.
 
The measurement can also be made continuously with an operating process. For instance, oil refineries measure the freeze point of diesel fuel online, meaning that the sample is taken from the process and measured automatically. This allows for more frequent measurements as the sample does not have to be manually collected and taken to a remote laboratory.
 
==Thermodynamics==
[[File:Melting curve of water.jpg|thumb|right|Pressure dependence of water melting point]]Not only is heat required to raise the temperature of the solid to the melting point, but the melting itself requires heat called the [[heat of fusion]].
 
From a thermodynamics point of view, at the melting point the change in [[Gibbs free energy]] (ΔG) of the material is zero, but the [[enthalpy]] (''H'') and the [[entropy]] (''S'') of the material are increasing (ΔH, ΔS > 0). Melting phenomenon happens when the Gibbs free energy of the liquid becomes lower than the solid for that material. At various pressures this happens at a specific temperature. It can also be shown that:
 
: <math>\Delta S = \frac {\Delta H} {T}</math>
 
Here ''T'', ''ΔS'' and ''ΔH'' are respectively the [[temperature]] at the melting point, change of [[entropy]] of melting and the change of [[enthalpy]] of melting.
 
The melting point is sensitive to extremely large changes in [[pressure]], but generally this sensitivity is orders of magnitude less than that for the [[boiling point]], because the solid-liquid transition represents only a small change in volume.<ref>The exact relationship is expressed in the [[Clausius-Clapeyron relation]].</ref><ref>{{cite web |url= http://mpec.sc.mahidol.ac.th/RADOK/physmath/PHYSICS/j10.htm |title= J10 Heat: Change of aggregate state of substances through change of heat content: Change of aggregate state of substances and the equation of Clapeyron-Clausius |accessdate= 2008-02-19}}</ref> If, as observed in most cases, a substance is more dense in the solid than in the liquid state, the melting point will increase with increases in pressure. Otherwise the reverse behavior occurs. Notably, this is the case of water, as illustrated graphically to the right, but also of Si, Ge, Ga, Bi. With extremely large changes in pressure, substantial changes to the melting point are observed. For example, the melting point of silicon at ambient pressure (0.1 MPa) is 1415 °C, but at pressures in excess of 10 GPa it decreases to 1000 °C.<ref>Tonkov, E. Yu. and Ponyatovsky, E. G. (2005) ''Phase Transformations of Elements Under High Pressure'', CRC Press, Boca Raton, p. 98 ISBN 0-8493-3367-9</ref>
Melting points are often used to characterize organic and inorganic compounds and to ascertain their [[wiktionary:Purity|purity]]. The melting point of a pure substance is always higher and has a smaller range than the melting point of an impure substance or, more generally, of mixtures. The higher the quantity of other components, the lower the melting point and the broader will be the melting point range, often referred to as the pasty range. The temperature at which melting begins for a mixture is known as the solidus while the temperature where melting is complete is called the liquidus. Eutectics are special types of mixtures that behave like single phases. They melt sharply at a constant temperature to form a liquid of the same composition. Alternatively, on cooling a liquid with the eutectic composition will solidify as uniformly dispersed, small (fine-grained) mixed crystals with the same composition.
 
In contrast to crystalline solids, [[glass]]es do not possess a melting point;
on heating they undergo a smooth [[glass transition]] into a [[viscous liquid]].
Upon further heating, they gradually soften, which can be characterized by certain [[softening point]]s.
 
==Freezing-point depression==
{{main|Freezing-point depression}}
 
The freezing point of a [[solvent]] is depressed when another compound is added, meaning that a [[solution]] has a lower freezing point than a pure solvent. This phenomenon is used in technical applications to avoid freezing, for instance by adding salt or ethylene glycol to water.
 
==Carnelley's Rule==
In [[organic chemistry]] '''Carnelley's Rule''', established in 1882 by Thomas Carnelley, stated that ''high [[molecular symmetry]] is associated with high melting point''.<ref>{{cite journal |title= Melting Point and Molecular Symmetry |journal= [[Journal of Chemical Education]] |page= 724 |volume= 77 |issue= 6 |year= 2000 |doi= 10.1021/ed077p724 |author=Brown, R. J. C. & R. F. C.|bibcode = 2000JChEd..77..724B }}</ref> Carnelley based his rule on examination of 15,000 chemical compounds. For example for three [[structural isomer]]s with [[molecular formula]] C<sub>5</sub>H<sub>12</sub> the melting point increases in the series [[isopentane]] −160 °C (113 K) [[n-pentane]] −129.8 °C (143 K) and [[neopentane]] −16.4 °C (256.8 K).<ref>[[#Haynes|Haynes]], pp. 6.153–155.</ref> Likewise in [[xylene]]s and also [[dichlorobenzene]]s the melting point increases in the order [[arene substitution patterns|meta, ortho and then para]]. [[Pyridine]] has a lower symmetry than [[benzene]] hence its lower melting point but the melting point again increases with [[diazine]] and [[triazine]]s. Many cage-like compounds like [[adamantane]] and [[cubane]] with high symmetry have relatively high melting points.
 
A high melting point results from a high [[heat of fusion]], a low [[entropy of fusion]], or a combination of both. In highly symmetrical molecules the crystal phase is densely packed with many efficient intermolecular interactions resulting in a higher enthalpy change on melting.
 
==Predicting the melting point of substances (Lindemann's criterion)==
An attempt to predict the bulk melting point of crystalline materials was first made in 1910 by [[Frederick Lindemann]].<ref name="Lindemann1910">{{cite journal |author=Lindemann FA |title=The calculation of molecular vibration frequencies |journal=Physik. Z. |volume=11 |year=1910 |pages=609–612 |authorlink=Frederick Lindemann}}</ref> The idea behind the theory was the observation that the average amplitude of thermal vibrations increases with increasing temperature. Melting initiates when the amplitude of vibration becomes large enough for adjacent atoms to partly occupy the same space. The '''Lindemann criterion''' states that melting is expected when the root mean square vibration amplitude exceeds a threshold value.
 
Assuming that all atoms in a crystal vibrate with the same frequency ''ν'', the average thermal energy can be estimated using the [[equipartition theorem]] as<ref name=Sorkin>Sorkin, S., (2003), [http://phycomp.technion.ac.il/~phsorkin/thesis/thesis.html Point defects, lattice structure, and melting], Thesis, Technion, Israel.</ref>
:<math>
E = 4\pi^2 m \nu^2~u^2 = k_B T
</math>
where ''m'' is the [[atomic mass]], ''ν'' is the [[frequency]], ''u'' is the average vibration amplitude, k<sub>B</sub> is the [[Boltzmann constant]], and ''T'' is the [[Thermodynamic temperature|absolute temperature]]. If the threshold value of ''u<sup>2</sup>'' is ''c<sup>2</sup>a<sup>2</sup>'' where ''c'' is the [[Lindemann index|Lindemann constant]] and ''a'' is the [[atomic spacing]], then the melting point is estimated as
:<math>
T_m = \cfrac{4\pi^2 m \nu^2 c^2 a^2}{k_B} .
</math>
Several other expressions for the estimated melting temperature can be obtained depending on the estimate of the average thermal energy. Another commonly used expression for the Lindemann criterion is<ref name=Hofmann>{{cite book|author=Philip Hofmann|title=Solid state physics: an introduction|url=http://books.google.com/books?id=XfIpxi4kcM4C&pg=PA67|accessdate=13 March 2011|year=2008|publisher=Wiley-VCH|isbn=978-3-527-40861-0|page=67}}</ref>
:<math>
T_m = \cfrac{m \nu^2 c^2 a^2}{k_B} .
</math>
From the expression for the [[Debye frequency]] for ''ν'', we have
:<math>
T_m = \cfrac{2\pi m c^2 a^2 \theta_D^2 k_B}{h^2}
</math>
where θ<sub>D</sub> is the [[Debye temperature]] and ''h'' is the [[Planck constant]]. Values of ''c'' range from 0.15–0.3 for most materials.<ref name=Nelson>Nelson, D. R., (2002), [http://books.google.com/books?id=YtYFAqswRzUC&printsec=frontcover Defects and geometry in condensed matter physics], Cambridge University Press, ISBN 0-521-00400-4</ref>
 
==Open melting point data==
In February 2011<ref name=Bradley>Bradley, J-C., (2011), [http://usefulchem.blogspot.com/2011/02/alfa-aesar-melting-point-data-now.html Alfa Aesar melting point data now openly available]</ref> [[Alfa Aesar]] released over 10,000 melting points of compounds from their catalog as [[open data]]. These data have been curated and are freely available for download.<ref name=BradleyLang>[http://lxsrv7.oru.edu/~alang/meltingpoints/download.php Open Melting Point Datasets]. Lxsrv7.oru.edu. Retrieved on 2013-09-13.</ref> These data have been used to create a [[random forest]] model for melting point prediction<ref name=Lang>Bradley, J-C. and Lang A.S.I.D. (2011) [http://onschallenge.wikispaces.com/MeltingPointModel010 Random Forest model for melting point prediction]. onschallenge.wikispaces.com</ref> which is now available as a free-to-use webservice.<ref name=LangGuha>[http://www.qsardb.org/repository/predictor/10967/104?model=rf Predict melting point from SMILES]. Qsardb.org. Retrieved on 2013-09-13.</ref> Highly curated and open melting point data are also available from [[Nature Precedings]].<ref name=Williams>[http://precedings.nature.com/documents/6229/version/1 ONS Open Melting Point Collection]. Precedings.nature.com. Retrieved on 2013-09-13.</ref>
 
==See also==
* [[Liquidus temperature]]
* [[List of elements by melting point]]
* [[Melting points of the elements (data page)]]
* [[Phase (matter)|Phases of matter]]
* [[Triple point]]
* [[Slip melting point]]
* [[Solidus temperature]]
 
==References==
{{reflist|30em}}
 
==Bibliography==
*{{cite book|ref=Haynes|editor=Haynes, William M.|year=2011|title= CRC Handbook of Chemistry and Physics |edition=92nd ed.|publisher= CRC Press|isbn=1439855110}}
 
==External links==
* [http://www.archive.org/details/meltingboilingpo01carnuoft Melting and boiling point tables vol. 1] by Thomas Carnelley (Harrison, London, 1885–1887)
* [http://www.archive.org/details/meltingboilingpo02carnuoft Melting and boiling point tables vol. 2] by Thomas Carnelley (Harrison, London, 1885–1887)
* [http://lxsrv7.oru.edu/~alang/meltingpoints/ ONS melting point explorer] Over 10,000 [[Open Data]] melting points.
 
{{State of matter}}
{{Use dmy dates|date=June 2011}}
 
{{DEFAULTSORT:Melting Point}}
[[Category:Atmospheric thermodynamics]]
[[Category:Concepts in physics]]
[[Category:Phase transitions]]
[[Category:Threshold temperatures]]

Revision as of 16:40, 24 January 2014

Template:For2

The melting point (or, rarely, liquefaction point) of a solid is the temperature at which it changes state from solid to liquid at atmospheric pressure. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends (usually slightly) on pressure and is usually specified at standard pressure. When considered as the temperature of the reverse change from liquid to solid, it is referred to as the freezing point or crystallization point. Because of the ability of some substances to supercool, the freezing point is not considered as a characteristic property of a substance. When the "characteristic freezing point" of a substance is determined, in fact the actual methodology is almost always "the principle of observing the disappearance rather than the formation of ice", that is, the melting point.[1]

Examples

Melting points (in blue) and boiling points (in pink) of the first eight carboxylic acids (°C)

For most substances, melting and freezing points are approximately equal. For example, the melting point and freezing point of mercury is 234.32 kelvin (−38.83 °C or −37.89 °F).[2] However, certain substances possess differing solid-liquid transition temperatures. For example, agar melts at 85 °C (185 °F) and solidifies from 31 °C to 40 °C (89.6 °F to 104 °F); such direction dependence is known as hysteresis.

The melting point of ice at 1 atmosphere of pressure is very close [3] to 0 °C (32 °F, 273.15 K); this is also known as the ice point. In the presence of nucleating substances the freezing point of water is the same as the melting point, but in the absence of nucleators water can supercool to −42 °C (−43.6 °F, 231 K) before freezing.

The chemical element with the highest melting point is tungsten, at 3687 K (3414 °C, 6177 °F)[4] making it excellent for use as filaments in light bulbs. The often-cited carbon does not melt at ambient pressure but sublimes at about 4000 K; a liquid phase only exists above pressures of 10 MPa and estimated 4300–4700 K (see Carbon phase diagram). Tantalum hafnium carbide (Ta4HfC5) is a refractory compound with a very high melting point of 4488 K (4215 °C, 7619 °F).[5] At the other end of the scale, helium does not freeze at all at normal pressure, even at temperatures very close to absolute zero; pressures over 20 times normal atmospheric pressure are necessary.

Melting point measurements

Mining Engineer (Excluding Oil ) Truman from Alma, loves to spend time knotting, largest property developers in singapore developers in singapore and stamp collecting. Recently had a family visit to Urnes Stave Church.

Kofler bench with samples for calibration

Many laboratory techniques exist for the determination of melting points. A Kofler bench is a metal strip with a temperature gradient (range from room temperature to 300 °C). Any substance can be placed on a section of the strip revealing its thermal behaviour at the temperature at that point. Differential scanning calorimetry gives information on melting point together with its enthalpy of fusion.

Automatic digital melting point meter

A basic melting point apparatus for the analysis of crystalline solids consists of an oil bath with a transparent window (most basic design: a Thiele tube) and a simple magnifier. The several grains of a solid are placed in a thin glass tube and partially immersed in the oil bath. The oil bath is heated (and stirred) and with the aid of the magnifier (and external light source) melting of the individual crystals at a certain temperature can be observed. In large/small devices, the sample is placed in a heating block, and optical detection is automated.

The measurement can also be made continuously with an operating process. For instance, oil refineries measure the freeze point of diesel fuel online, meaning that the sample is taken from the process and measured automatically. This allows for more frequent measurements as the sample does not have to be manually collected and taken to a remote laboratory.

Thermodynamics

Pressure dependence of water melting point

Not only is heat required to raise the temperature of the solid to the melting point, but the melting itself requires heat called the heat of fusion.

From a thermodynamics point of view, at the melting point the change in Gibbs free energy (ΔG) of the material is zero, but the enthalpy (H) and the entropy (S) of the material are increasing (ΔH, ΔS > 0). Melting phenomenon happens when the Gibbs free energy of the liquid becomes lower than the solid for that material. At various pressures this happens at a specific temperature. It can also be shown that:

Here T, ΔS and ΔH are respectively the temperature at the melting point, change of entropy of melting and the change of enthalpy of melting.

The melting point is sensitive to extremely large changes in pressure, but generally this sensitivity is orders of magnitude less than that for the boiling point, because the solid-liquid transition represents only a small change in volume.[6][7] If, as observed in most cases, a substance is more dense in the solid than in the liquid state, the melting point will increase with increases in pressure. Otherwise the reverse behavior occurs. Notably, this is the case of water, as illustrated graphically to the right, but also of Si, Ge, Ga, Bi. With extremely large changes in pressure, substantial changes to the melting point are observed. For example, the melting point of silicon at ambient pressure (0.1 MPa) is 1415 °C, but at pressures in excess of 10 GPa it decreases to 1000 °C.[8] Melting points are often used to characterize organic and inorganic compounds and to ascertain their purity. The melting point of a pure substance is always higher and has a smaller range than the melting point of an impure substance or, more generally, of mixtures. The higher the quantity of other components, the lower the melting point and the broader will be the melting point range, often referred to as the pasty range. The temperature at which melting begins for a mixture is known as the solidus while the temperature where melting is complete is called the liquidus. Eutectics are special types of mixtures that behave like single phases. They melt sharply at a constant temperature to form a liquid of the same composition. Alternatively, on cooling a liquid with the eutectic composition will solidify as uniformly dispersed, small (fine-grained) mixed crystals with the same composition.

In contrast to crystalline solids, glasses do not possess a melting point; on heating they undergo a smooth glass transition into a viscous liquid. Upon further heating, they gradually soften, which can be characterized by certain softening points.

Freezing-point depression

Mining Engineer (Excluding Oil ) Truman from Alma, loves to spend time knotting, largest property developers in singapore developers in singapore and stamp collecting. Recently had a family visit to Urnes Stave Church.

The freezing point of a solvent is depressed when another compound is added, meaning that a solution has a lower freezing point than a pure solvent. This phenomenon is used in technical applications to avoid freezing, for instance by adding salt or ethylene glycol to water.

Carnelley's Rule

In organic chemistry Carnelley's Rule, established in 1882 by Thomas Carnelley, stated that high molecular symmetry is associated with high melting point.[9] Carnelley based his rule on examination of 15,000 chemical compounds. For example for three structural isomers with molecular formula C5H12 the melting point increases in the series isopentane −160 °C (113 K) n-pentane −129.8 °C (143 K) and neopentane −16.4 °C (256.8 K).[10] Likewise in xylenes and also dichlorobenzenes the melting point increases in the order meta, ortho and then para. Pyridine has a lower symmetry than benzene hence its lower melting point but the melting point again increases with diazine and triazines. Many cage-like compounds like adamantane and cubane with high symmetry have relatively high melting points.

A high melting point results from a high heat of fusion, a low entropy of fusion, or a combination of both. In highly symmetrical molecules the crystal phase is densely packed with many efficient intermolecular interactions resulting in a higher enthalpy change on melting.

Predicting the melting point of substances (Lindemann's criterion)

An attempt to predict the bulk melting point of crystalline materials was first made in 1910 by Frederick Lindemann.[11] The idea behind the theory was the observation that the average amplitude of thermal vibrations increases with increasing temperature. Melting initiates when the amplitude of vibration becomes large enough for adjacent atoms to partly occupy the same space. The Lindemann criterion states that melting is expected when the root mean square vibration amplitude exceeds a threshold value.

Assuming that all atoms in a crystal vibrate with the same frequency ν, the average thermal energy can be estimated using the equipartition theorem as[12]

where m is the atomic mass, ν is the frequency, u is the average vibration amplitude, kB is the Boltzmann constant, and T is the absolute temperature. If the threshold value of u2 is c2a2 where c is the Lindemann constant and a is the atomic spacing, then the melting point is estimated as

Several other expressions for the estimated melting temperature can be obtained depending on the estimate of the average thermal energy. Another commonly used expression for the Lindemann criterion is[13]

From the expression for the Debye frequency for ν, we have

where θD is the Debye temperature and h is the Planck constant. Values of c range from 0.15–0.3 for most materials.[14]

Open melting point data

In February 2011[15] Alfa Aesar released over 10,000 melting points of compounds from their catalog as open data. These data have been curated and are freely available for download.[16] These data have been used to create a random forest model for melting point prediction[17] which is now available as a free-to-use webservice.[18] Highly curated and open melting point data are also available from Nature Precedings.[19]

See also

References

43 year old Petroleum Engineer Harry from Deep River, usually spends time with hobbies and interests like renting movies, property developers in singapore new condominium and vehicle racing. Constantly enjoys going to destinations like Camino Real de Tierra Adentro.

Bibliography

  • 20 year-old Real Estate Agent Rusty from Saint-Paul, has hobbies and interests which includes monopoly, property developers in singapore and poker. Will soon undertake a contiki trip that may include going to the Lower Valley of the Omo.

    My blog: http://www.primaboinca.com/view_profile.php?userid=5889534

External links

Template:State of matter 30 year-old Entertainer or Range Artist Wesley from Drumheller, really loves vehicle, property developers properties for sale in singapore singapore and horse racing. Finds inspiration by traveling to Works of Antoni Gaudí.

  1. One of the biggest reasons investing in a Singapore new launch is an effective things is as a result of it is doable to be lent massive quantities of money at very low interest rates that you should utilize to purchase it. Then, if property values continue to go up, then you'll get a really high return on funding (ROI). Simply make sure you purchase one of the higher properties, reminiscent of the ones at Fernvale the Riverbank or any Singapore landed property Get Earnings by means of Renting

    In its statement, the singapore property listing - website link, government claimed that the majority citizens buying their first residence won't be hurt by the new measures. Some concessions can even be prolonged to chose teams of consumers, similar to married couples with a minimum of one Singaporean partner who are purchasing their second property so long as they intend to promote their first residential property. Lower the LTV limit on housing loans granted by monetary establishments regulated by MAS from 70% to 60% for property purchasers who are individuals with a number of outstanding housing loans on the time of the brand new housing purchase. Singapore Property Measures - 30 August 2010 The most popular seek for the number of bedrooms in Singapore is 4, followed by 2 and three. Lush Acres EC @ Sengkang

    Discover out more about real estate funding in the area, together with info on international funding incentives and property possession. Many Singaporeans have been investing in property across the causeway in recent years, attracted by comparatively low prices. However, those who need to exit their investments quickly are likely to face significant challenges when trying to sell their property – and could finally be stuck with a property they can't sell. Career improvement programmes, in-house valuation, auctions and administrative help, venture advertising and marketing, skilled talks and traisning are continuously planned for the sales associates to help them obtain better outcomes for his or her shoppers while at Knight Frank Singapore. No change Present Rules

    Extending the tax exemption would help. The exemption, which may be as a lot as $2 million per family, covers individuals who negotiate a principal reduction on their existing mortgage, sell their house short (i.e., for lower than the excellent loans), or take part in a foreclosure course of. An extension of theexemption would seem like a common-sense means to assist stabilize the housing market, but the political turmoil around the fiscal-cliff negotiations means widespread sense could not win out. Home Minority Chief Nancy Pelosi (D-Calif.) believes that the mortgage relief provision will be on the table during the grand-cut price talks, in response to communications director Nadeam Elshami. Buying or promoting of blue mild bulbs is unlawful.

    A vendor's stamp duty has been launched on industrial property for the primary time, at rates ranging from 5 per cent to 15 per cent. The Authorities might be trying to reassure the market that they aren't in opposition to foreigners and PRs investing in Singapore's property market. They imposed these measures because of extenuating components available in the market." The sale of new dual-key EC models will even be restricted to multi-generational households only. The models have two separate entrances, permitting grandparents, for example, to dwell separately. The vendor's stamp obligation takes effect right this moment and applies to industrial property and plots which might be offered inside three years of the date of buy. JLL named Best Performing Property Brand for second year running

    The data offered is for normal info purposes only and isn't supposed to be personalised investment or monetary advice. Motley Fool Singapore contributor Stanley Lim would not personal shares in any corporations talked about. Singapore private home costs increased by 1.eight% within the fourth quarter of 2012, up from 0.6% within the earlier quarter. Resale prices of government-built HDB residences which are usually bought by Singaporeans, elevated by 2.5%, quarter on quarter, the quickest acquire in five quarters. And industrial property, prices are actually double the levels of three years ago. No withholding tax in the event you sell your property. All your local information regarding vital HDB policies, condominium launches, land growth, commercial property and more

    There are various methods to go about discovering the precise property. Some local newspapers (together with the Straits Instances ) have categorised property sections and many local property brokers have websites. Now there are some specifics to consider when buying a 'new launch' rental. Intended use of the unit Every sale begins with 10 p.c low cost for finish of season sale; changes to 20 % discount storewide; follows by additional reduction of fiftyand ends with last discount of 70 % or extra. Typically there is even a warehouse sale or transferring out sale with huge mark-down of costs for stock clearance. Deborah Regulation from Expat Realtor shares her property market update, plus prime rental residences and houses at the moment available to lease Esparina EC @ Sengkang
  2. Haynes, p. 4.122.
  3. The melting point of purified water has been measured as 0.002519 ± 0.000002 °C, see One of the biggest reasons investing in a Singapore new launch is an effective things is as a result of it is doable to be lent massive quantities of money at very low interest rates that you should utilize to purchase it. Then, if property values continue to go up, then you'll get a really high return on funding (ROI). Simply make sure you purchase one of the higher properties, reminiscent of the ones at Fernvale the Riverbank or any Singapore landed property Get Earnings by means of Renting

    In its statement, the singapore property listing - website link, government claimed that the majority citizens buying their first residence won't be hurt by the new measures. Some concessions can even be prolonged to chose teams of consumers, similar to married couples with a minimum of one Singaporean partner who are purchasing their second property so long as they intend to promote their first residential property. Lower the LTV limit on housing loans granted by monetary establishments regulated by MAS from 70% to 60% for property purchasers who are individuals with a number of outstanding housing loans on the time of the brand new housing purchase. Singapore Property Measures - 30 August 2010 The most popular seek for the number of bedrooms in Singapore is 4, followed by 2 and three. Lush Acres EC @ Sengkang

    Discover out more about real estate funding in the area, together with info on international funding incentives and property possession. Many Singaporeans have been investing in property across the causeway in recent years, attracted by comparatively low prices. However, those who need to exit their investments quickly are likely to face significant challenges when trying to sell their property – and could finally be stuck with a property they can't sell. Career improvement programmes, in-house valuation, auctions and administrative help, venture advertising and marketing, skilled talks and traisning are continuously planned for the sales associates to help them obtain better outcomes for his or her shoppers while at Knight Frank Singapore. No change Present Rules

    Extending the tax exemption would help. The exemption, which may be as a lot as $2 million per family, covers individuals who negotiate a principal reduction on their existing mortgage, sell their house short (i.e., for lower than the excellent loans), or take part in a foreclosure course of. An extension of theexemption would seem like a common-sense means to assist stabilize the housing market, but the political turmoil around the fiscal-cliff negotiations means widespread sense could not win out. Home Minority Chief Nancy Pelosi (D-Calif.) believes that the mortgage relief provision will be on the table during the grand-cut price talks, in response to communications director Nadeam Elshami. Buying or promoting of blue mild bulbs is unlawful.

    A vendor's stamp duty has been launched on industrial property for the primary time, at rates ranging from 5 per cent to 15 per cent. The Authorities might be trying to reassure the market that they aren't in opposition to foreigners and PRs investing in Singapore's property market. They imposed these measures because of extenuating components available in the market." The sale of new dual-key EC models will even be restricted to multi-generational households only. The models have two separate entrances, permitting grandparents, for example, to dwell separately. The vendor's stamp obligation takes effect right this moment and applies to industrial property and plots which might be offered inside three years of the date of buy. JLL named Best Performing Property Brand for second year running

    The data offered is for normal info purposes only and isn't supposed to be personalised investment or monetary advice. Motley Fool Singapore contributor Stanley Lim would not personal shares in any corporations talked about. Singapore private home costs increased by 1.eight% within the fourth quarter of 2012, up from 0.6% within the earlier quarter. Resale prices of government-built HDB residences which are usually bought by Singaporeans, elevated by 2.5%, quarter on quarter, the quickest acquire in five quarters. And industrial property, prices are actually double the levels of three years ago. No withholding tax in the event you sell your property. All your local information regarding vital HDB policies, condominium launches, land growth, commercial property and more

    There are various methods to go about discovering the precise property. Some local newspapers (together with the Straits Instances ) have categorised property sections and many local property brokers have websites. Now there are some specifics to consider when buying a 'new launch' rental. Intended use of the unit Every sale begins with 10 p.c low cost for finish of season sale; changes to 20 % discount storewide; follows by additional reduction of fiftyand ends with last discount of 70 % or extra. Typically there is even a warehouse sale or transferring out sale with huge mark-down of costs for stock clearance. Deborah Regulation from Expat Realtor shares her property market update, plus prime rental residences and houses at the moment available to lease Esparina EC @ Sengkang
  4. Haynes, p. 4.123.
  5. One of the biggest reasons investing in a Singapore new launch is an effective things is as a result of it is doable to be lent massive quantities of money at very low interest rates that you should utilize to purchase it. Then, if property values continue to go up, then you'll get a really high return on funding (ROI). Simply make sure you purchase one of the higher properties, reminiscent of the ones at Fernvale the Riverbank or any Singapore landed property Get Earnings by means of Renting

    In its statement, the singapore property listing - website link, government claimed that the majority citizens buying their first residence won't be hurt by the new measures. Some concessions can even be prolonged to chose teams of consumers, similar to married couples with a minimum of one Singaporean partner who are purchasing their second property so long as they intend to promote their first residential property. Lower the LTV limit on housing loans granted by monetary establishments regulated by MAS from 70% to 60% for property purchasers who are individuals with a number of outstanding housing loans on the time of the brand new housing purchase. Singapore Property Measures - 30 August 2010 The most popular seek for the number of bedrooms in Singapore is 4, followed by 2 and three. Lush Acres EC @ Sengkang

    Discover out more about real estate funding in the area, together with info on international funding incentives and property possession. Many Singaporeans have been investing in property across the causeway in recent years, attracted by comparatively low prices. However, those who need to exit their investments quickly are likely to face significant challenges when trying to sell their property – and could finally be stuck with a property they can't sell. Career improvement programmes, in-house valuation, auctions and administrative help, venture advertising and marketing, skilled talks and traisning are continuously planned for the sales associates to help them obtain better outcomes for his or her shoppers while at Knight Frank Singapore. No change Present Rules

    Extending the tax exemption would help. The exemption, which may be as a lot as $2 million per family, covers individuals who negotiate a principal reduction on their existing mortgage, sell their house short (i.e., for lower than the excellent loans), or take part in a foreclosure course of. An extension of theexemption would seem like a common-sense means to assist stabilize the housing market, but the political turmoil around the fiscal-cliff negotiations means widespread sense could not win out. Home Minority Chief Nancy Pelosi (D-Calif.) believes that the mortgage relief provision will be on the table during the grand-cut price talks, in response to communications director Nadeam Elshami. Buying or promoting of blue mild bulbs is unlawful.

    A vendor's stamp duty has been launched on industrial property for the primary time, at rates ranging from 5 per cent to 15 per cent. The Authorities might be trying to reassure the market that they aren't in opposition to foreigners and PRs investing in Singapore's property market. They imposed these measures because of extenuating components available in the market." The sale of new dual-key EC models will even be restricted to multi-generational households only. The models have two separate entrances, permitting grandparents, for example, to dwell separately. The vendor's stamp obligation takes effect right this moment and applies to industrial property and plots which might be offered inside three years of the date of buy. JLL named Best Performing Property Brand for second year running

    The data offered is for normal info purposes only and isn't supposed to be personalised investment or monetary advice. Motley Fool Singapore contributor Stanley Lim would not personal shares in any corporations talked about. Singapore private home costs increased by 1.eight% within the fourth quarter of 2012, up from 0.6% within the earlier quarter. Resale prices of government-built HDB residences which are usually bought by Singaporeans, elevated by 2.5%, quarter on quarter, the quickest acquire in five quarters. And industrial property, prices are actually double the levels of three years ago. No withholding tax in the event you sell your property. All your local information regarding vital HDB policies, condominium launches, land growth, commercial property and more

    There are various methods to go about discovering the precise property. Some local newspapers (together with the Straits Instances ) have categorised property sections and many local property brokers have websites. Now there are some specifics to consider when buying a 'new launch' rental. Intended use of the unit Every sale begins with 10 p.c low cost for finish of season sale; changes to 20 % discount storewide; follows by additional reduction of fiftyand ends with last discount of 70 % or extra. Typically there is even a warehouse sale or transferring out sale with huge mark-down of costs for stock clearance. Deborah Regulation from Expat Realtor shares her property market update, plus prime rental residences and houses at the moment available to lease Esparina EC @ Sengkang
  6. The exact relationship is expressed in the Clausius-Clapeyron relation.
  7. Template:Cite web
  8. Tonkov, E. Yu. and Ponyatovsky, E. G. (2005) Phase Transformations of Elements Under High Pressure, CRC Press, Boca Raton, p. 98 ISBN 0-8493-3367-9
  9. One of the biggest reasons investing in a Singapore new launch is an effective things is as a result of it is doable to be lent massive quantities of money at very low interest rates that you should utilize to purchase it. Then, if property values continue to go up, then you'll get a really high return on funding (ROI). Simply make sure you purchase one of the higher properties, reminiscent of the ones at Fernvale the Riverbank or any Singapore landed property Get Earnings by means of Renting

    In its statement, the singapore property listing - website link, government claimed that the majority citizens buying their first residence won't be hurt by the new measures. Some concessions can even be prolonged to chose teams of consumers, similar to married couples with a minimum of one Singaporean partner who are purchasing their second property so long as they intend to promote their first residential property. Lower the LTV limit on housing loans granted by monetary establishments regulated by MAS from 70% to 60% for property purchasers who are individuals with a number of outstanding housing loans on the time of the brand new housing purchase. Singapore Property Measures - 30 August 2010 The most popular seek for the number of bedrooms in Singapore is 4, followed by 2 and three. Lush Acres EC @ Sengkang

    Discover out more about real estate funding in the area, together with info on international funding incentives and property possession. Many Singaporeans have been investing in property across the causeway in recent years, attracted by comparatively low prices. However, those who need to exit their investments quickly are likely to face significant challenges when trying to sell their property – and could finally be stuck with a property they can't sell. Career improvement programmes, in-house valuation, auctions and administrative help, venture advertising and marketing, skilled talks and traisning are continuously planned for the sales associates to help them obtain better outcomes for his or her shoppers while at Knight Frank Singapore. No change Present Rules

    Extending the tax exemption would help. The exemption, which may be as a lot as $2 million per family, covers individuals who negotiate a principal reduction on their existing mortgage, sell their house short (i.e., for lower than the excellent loans), or take part in a foreclosure course of. An extension of theexemption would seem like a common-sense means to assist stabilize the housing market, but the political turmoil around the fiscal-cliff negotiations means widespread sense could not win out. Home Minority Chief Nancy Pelosi (D-Calif.) believes that the mortgage relief provision will be on the table during the grand-cut price talks, in response to communications director Nadeam Elshami. Buying or promoting of blue mild bulbs is unlawful.

    A vendor's stamp duty has been launched on industrial property for the primary time, at rates ranging from 5 per cent to 15 per cent. The Authorities might be trying to reassure the market that they aren't in opposition to foreigners and PRs investing in Singapore's property market. They imposed these measures because of extenuating components available in the market." The sale of new dual-key EC models will even be restricted to multi-generational households only. The models have two separate entrances, permitting grandparents, for example, to dwell separately. The vendor's stamp obligation takes effect right this moment and applies to industrial property and plots which might be offered inside three years of the date of buy. JLL named Best Performing Property Brand for second year running

    The data offered is for normal info purposes only and isn't supposed to be personalised investment or monetary advice. Motley Fool Singapore contributor Stanley Lim would not personal shares in any corporations talked about. Singapore private home costs increased by 1.eight% within the fourth quarter of 2012, up from 0.6% within the earlier quarter. Resale prices of government-built HDB residences which are usually bought by Singaporeans, elevated by 2.5%, quarter on quarter, the quickest acquire in five quarters. And industrial property, prices are actually double the levels of three years ago. No withholding tax in the event you sell your property. All your local information regarding vital HDB policies, condominium launches, land growth, commercial property and more

    There are various methods to go about discovering the precise property. Some local newspapers (together with the Straits Instances ) have categorised property sections and many local property brokers have websites. Now there are some specifics to consider when buying a 'new launch' rental. Intended use of the unit Every sale begins with 10 p.c low cost for finish of season sale; changes to 20 % discount storewide; follows by additional reduction of fiftyand ends with last discount of 70 % or extra. Typically there is even a warehouse sale or transferring out sale with huge mark-down of costs for stock clearance. Deborah Regulation from Expat Realtor shares her property market update, plus prime rental residences and houses at the moment available to lease Esparina EC @ Sengkang
  10. Haynes, pp. 6.153–155.
  11. One of the biggest reasons investing in a Singapore new launch is an effective things is as a result of it is doable to be lent massive quantities of money at very low interest rates that you should utilize to purchase it. Then, if property values continue to go up, then you'll get a really high return on funding (ROI). Simply make sure you purchase one of the higher properties, reminiscent of the ones at Fernvale the Riverbank or any Singapore landed property Get Earnings by means of Renting

    In its statement, the singapore property listing - website link, government claimed that the majority citizens buying their first residence won't be hurt by the new measures. Some concessions can even be prolonged to chose teams of consumers, similar to married couples with a minimum of one Singaporean partner who are purchasing their second property so long as they intend to promote their first residential property. Lower the LTV limit on housing loans granted by monetary establishments regulated by MAS from 70% to 60% for property purchasers who are individuals with a number of outstanding housing loans on the time of the brand new housing purchase. Singapore Property Measures - 30 August 2010 The most popular seek for the number of bedrooms in Singapore is 4, followed by 2 and three. Lush Acres EC @ Sengkang

    Discover out more about real estate funding in the area, together with info on international funding incentives and property possession. Many Singaporeans have been investing in property across the causeway in recent years, attracted by comparatively low prices. However, those who need to exit their investments quickly are likely to face significant challenges when trying to sell their property – and could finally be stuck with a property they can't sell. Career improvement programmes, in-house valuation, auctions and administrative help, venture advertising and marketing, skilled talks and traisning are continuously planned for the sales associates to help them obtain better outcomes for his or her shoppers while at Knight Frank Singapore. No change Present Rules

    Extending the tax exemption would help. The exemption, which may be as a lot as $2 million per family, covers individuals who negotiate a principal reduction on their existing mortgage, sell their house short (i.e., for lower than the excellent loans), or take part in a foreclosure course of. An extension of theexemption would seem like a common-sense means to assist stabilize the housing market, but the political turmoil around the fiscal-cliff negotiations means widespread sense could not win out. Home Minority Chief Nancy Pelosi (D-Calif.) believes that the mortgage relief provision will be on the table during the grand-cut price talks, in response to communications director Nadeam Elshami. Buying or promoting of blue mild bulbs is unlawful.

    A vendor's stamp duty has been launched on industrial property for the primary time, at rates ranging from 5 per cent to 15 per cent. The Authorities might be trying to reassure the market that they aren't in opposition to foreigners and PRs investing in Singapore's property market. They imposed these measures because of extenuating components available in the market." The sale of new dual-key EC models will even be restricted to multi-generational households only. The models have two separate entrances, permitting grandparents, for example, to dwell separately. The vendor's stamp obligation takes effect right this moment and applies to industrial property and plots which might be offered inside three years of the date of buy. JLL named Best Performing Property Brand for second year running

    The data offered is for normal info purposes only and isn't supposed to be personalised investment or monetary advice. Motley Fool Singapore contributor Stanley Lim would not personal shares in any corporations talked about. Singapore private home costs increased by 1.eight% within the fourth quarter of 2012, up from 0.6% within the earlier quarter. Resale prices of government-built HDB residences which are usually bought by Singaporeans, elevated by 2.5%, quarter on quarter, the quickest acquire in five quarters. And industrial property, prices are actually double the levels of three years ago. No withholding tax in the event you sell your property. All your local information regarding vital HDB policies, condominium launches, land growth, commercial property and more

    There are various methods to go about discovering the precise property. Some local newspapers (together with the Straits Instances ) have categorised property sections and many local property brokers have websites. Now there are some specifics to consider when buying a 'new launch' rental. Intended use of the unit Every sale begins with 10 p.c low cost for finish of season sale; changes to 20 % discount storewide; follows by additional reduction of fiftyand ends with last discount of 70 % or extra. Typically there is even a warehouse sale or transferring out sale with huge mark-down of costs for stock clearance. Deborah Regulation from Expat Realtor shares her property market update, plus prime rental residences and houses at the moment available to lease Esparina EC @ Sengkang
  12. Sorkin, S., (2003), Point defects, lattice structure, and melting, Thesis, Technion, Israel.
  13. 20 year-old Real Estate Agent Rusty from Saint-Paul, has hobbies and interests which includes monopoly, property developers in singapore and poker. Will soon undertake a contiki trip that may include going to the Lower Valley of the Omo.

    My blog: http://www.primaboinca.com/view_profile.php?userid=5889534
  14. Nelson, D. R., (2002), Defects and geometry in condensed matter physics, Cambridge University Press, ISBN 0-521-00400-4
  15. Bradley, J-C., (2011), Alfa Aesar melting point data now openly available
  16. Open Melting Point Datasets. Lxsrv7.oru.edu. Retrieved on 2013-09-13.
  17. Bradley, J-C. and Lang A.S.I.D. (2011) Random Forest model for melting point prediction. onschallenge.wikispaces.com
  18. Predict melting point from SMILES. Qsardb.org. Retrieved on 2013-09-13.
  19. ONS Open Melting Point Collection. Precedings.nature.com. Retrieved on 2013-09-13.