Melting/boiling points of elements

Is there a scientific reason (i.e., not editorial, not because I’m a moron, etc.) different resources differ in the boiling points of elements?

I’m trying to edit a series of lesson plans for chemistry teachers. The author has made a table of elements that has melting and boiling points. In verifying the information, I find that Webelements lists the melting point of Carbon as 3527 °C, while Chemicalelements lists it at 4827.0 °C. This is not the only example of various Web pages listing things differently. What am I missing?
As a side/bonus question; she also has “Ratio with H 1:2” for Carbon (and other ratios for other elements). What the heck is that?



4827 is the boiling point in your second cite, it lists the Melting Point: 3500.0 °C (3773.15 K, 6332.0 °F)


Your first source has:

and your second has:

That’s only 27 degrees difference in the melting points, but it is 800 degrees difference in the boiling points: were you concerned about the latter?

:smack: knew it could be the moron option!

But… but… but it took a bit of confusion before I thought to post here. Check out Krypton at Webelements with a melting point of -157.36 °C, and Chemicalelements with a melting point of -157.2 °C (If I have it right this time). Rounding doesn’t account (again, allowing for the moron factor) for getting from one to the other. I thought melting points were static at a standard atmosphere, and accepted as a constant. Or is the melting point a range?

Your worried about the difference between -157.36 ˚C and -157.2 ˚C? That sort of difference could be just slightly different experimental setup (determinate error). It could also just be that the measurements have an inherent uncertainty in them (indeterminate error). It would be very difficult to make these measurements at ± 0.01 ˚C. If these measurements were reported in a journal they would be reported with the error. If you really want to reconcile these two measurements you will have to consult the original source.

It is, however, a good lesson for the kids on uncertainty in measurements. It is a very important topic for people to learn. In todays calculator world, we can do the arithmatic to 10 decimal places, but often forget that only the first two are meaningful.

Have you ever gotten a noble gas to freeze? I can’t imagine that it’d be an easy process, and there’s probably plenty of experimental error involved. Looking at it that way, the difference between -157.36 and -157.2 doesn’t seem like all that much. Maybe one result is older than the other, and the new experiments have it pinned down a bit more precisely. Or maybe both results are up to date, and it’s not clear which one is more reliable. Or maybe the error bars are large enough that both can be considered equally reliable, and in agreement.

Oh, not worried per se, just fact checking. My intuition was that melting/boiling points were immutable facts, something that could be derived from other properties or something. So even though it’s a small disparity it struck me as their mistake (unlikely), my stupidity (good chance), or my ignorance (fought today). Thanks for chiming in!

Melting points are dependent on the form of the element: carbon bucky balls, nanotubes, graphite and diamond will have different metling points because of a different bond energies. I’m not sure how tables such as this choose which form they give the melting point for. Anyone know?

Boiling points will depend on the pressure. Tables will typically standardize this at a standard atmosphere, but it can’t hurt to check.

Both points will vary based on isotope as well. Usually the given numbers will be for the elements’ naturally occurring isotopic ratio, but again it doesn’t hurt to check.