Talk:Melting point

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Hi,

As just a student, I wanted to offer something I believe may be helpful to the average person looking for info on melting points.

I have always been taught that the melting point is the temperature at which liquid and solid exist in equilibrium with each other. I believe this would help explain why the change in Gibbs Free E is zero at the melting point because the system is in equilibrium.(?) Also, that if a melting point is reported as a single value it is understood to be the upper limit of the temperature range.

I believe it would be useful to explain why the mp is higher and tighter for pure substances, why does an impurity lower the mp and also mention the eutetic point for binary systems.

While it is an interesting tidbit about tungsten and carbon, I don't think this is why most people would search for melting point information. Also when reading this page, I felt like the author(s) where defending themselves against an attack....this was a major portion of the talk page....when really explaining melting point might have been a better.

Again this is only the viewpoint of a few students and not intended to disrespect the author(s) California SU (talk) 08:55, 28 December 2007 (UTC)

Contents

[edit] Crystalline M..P vs. Amporphous M.P.

I had thought that Crystalline solids melt at specific temperatures and it was only Amorphous solids that melt over a range of temperatures. This is due to the different strengths of intermolecular forces within Amorphous solids where as Crystalline solids have the same strength of intermolecular forces allowing them to break bonds at the same time. Is this not correct?AcrosstheSea=w= 30 April 2007


[edit] melting vs. freezing point

I'm not sure whether the melting point is for all substances the equivalent of the freezing point as stated in this article.

  • you are correct in fact. for example, agar solidifes at ~55C but melts at a higher temperature. i will work on this later when i have the time because it is very important. good find. -- Bubbachuck 17:49, 12 August 2005 (UTC)
This same problem exists in the article for Melting, where I flagged it awhile back. Would you fix it there, too, please and remove my dubious flag from that article. Thanks. PS. Someone else noticed it in this article. I sign my posts. 5Q5 14:39, 13 March 2007 (UTC)

[edit] Tungsten doesnt have the highest melting point of all elements

Tungsten doesnt have the highest melting point of all elements, it has the highest melting point of all metals. Carbon (melting point of 3823 K) has the highest melting point of all elements. However, Tungsten does have the highest boiling point. —The preceding unsigned comment was added by 24.242.200.33 (talk • contribs) 10:31, 7 February 2006 (UTC).

Carbon at ambient pressure does not melt but sublimates. A liquid phase only exists above 10 MPa. Femto 13:27, 7 February 2006 (UTC)


If we don't restrict this to elements and allow compounds, there's tantalum hafnium carbide (Ta4HfC5) with a m.p. of 4215 °C [1]. (Note though that even Britannica weasels around calling it "the" highest.) Femto 13:27, 7 February 2006 (UTC)

[edit] Crystalline solids only?

Message from OTRS: "The melting point is a characteristic of only crystalline solids, not all solids."

Amorphous solid materials may have a glass transition to which a fictive temperature can be attributed but many do not have even that.

[edit] Pure Substance

"The melting point of a pure substance is always higher than the melting point of that substance when a small amount of an impurity is present." Is this really true? Does it need qualification? Is this related to the unexplained phrase "melting-point depression" mentioned on the Lauric acid page? --Elijah 20:59, 25 August 2006 (UTC)

"Yes as far as I know and also based on first principles", "I don't think so", abd "exactly", respectively. Melting point depression is the phenomenon that impurities lower the melting point of a pure substance. DMacks 16:13, 28 August 2006 (UTC)
Then could someone more knowledgeable about the subject include that here in a way that articles like the lauric acid one could link to it? --Elijah 05:21, 29 August 2006 (UTC)

[edit] Picture of melting point vs pressure.

Should we perhaps change this from water to some other compound? Water is in the minority in that its melting point decreases with pressure, which could be misleading. Capuchin 11:52, 17 July 2007 (UTC)

[edit] Proposed merger

I oppose the proposal to merge this article (MP) with Melting. As an organic chemist, I see MP as a standard test that is done on compounds to ascertain their identity and purity. There are all sorts of rules that go along with that, relating to molecular size, symmetry, polarity, and it can be related to solubility. All that material deserves an article by itself. Melting is a phenomenon, a much broader subject than MP, and the article can describe the molecular forces, the physical chemistry of melting, effect of temperature and pressure, etc., latent heat of fusion, etc. MP can be covered as a paragraph within that article, using the summary style. Walkerma 20:42, 29 July 2007 (UTC)

In other words, if there had to be a merger it would be melting point into melting, not the current (reverse) proposal. Richard001 00:07, 15 September 2007 (UTC)

I strongly oppose the merging of the two articles. See boiling and boiling point for great examples on how to seperate those two words. "Boiling" is described as the action of heating a liquid up to its boiling point, while "boiling point" describes the matter of state and the significance of the boiling point itself. The exact same thing could and should be done for melting and melting point Francis The Bird 11:04, 2 October 2007 (UTC)

[edit] Melting point, disambiguated

There should be another article for "Melting Point", this second one referring to the rock group out of Berkeley, CA. Citations and more information can be found at www.meltingpointband.com.

[edit] WikiProject class rating

This article was automatically assessed because at least one WikiProject had rated the article as start, and the rating on other projects was brought up to start class. BetacommandBot 10:00, 10 November 2007 (UTC)