30
votes
Accepted
Why is the melting point of PCl3 less than that of PCl5?
Because $\ce{PCl5}$ does something which is not immediately obvious from its molecular formula: it autoionizes and becomes an ionic solid $\ce{PCl4+PCl6-}$. As such, it has much stronger interactions ...
- 31.2k
30
votes
What easily accessible material has melting point between 500 °C and 590 °C?
Temperature-indicating or thermo crayons are used by welders. These melt at specific temperatures.
Not as an endorsement, but to give you an idea of what's available, the crayons from McMaster-Carr ...
- 401
22
votes
Is honey really a supersaturated solution? Does heating to un-crystalize redissolve it or melt it?
Honey is indeed a complex mixture containing more than hundred compounds.
As for Wikipedia and depending on the point of view it is
a supersatured liquid solution
a viscous supercooled liquid (in ...
- 3,626
20
votes
Accepted
Melting point of aspirin, contradicting sources
Wolfram company doesn't conduct any experimental determinations of physical constants for chemical compounds and uses literature data sources.
The webpage for ChemicalData Source Information lists ...
- 37.6k
18
votes
Is honey really a supersaturated solution? Does heating to un-crystalize redissolve it or melt it?
Melting and dissolving are all the same when you look at mixtures close to saturation.
You can say water lowers the melting point of the sugar, or that the solubility of sugar increases with ...
- 12.1k
18
votes
What easily accessible material has melting point between 500 °C and 590 °C?
It might not qualify as 'available at home' but MakeItFrom has a database with engineering material you can search:
MakeItFrom.com is a curated database of engineering material properties that ...
- 2,075
16
votes
How can steel be so different from iron, even if amount of carbon is small?
One of the key considerations is that much of the interesting mechanical behaviour doesn't occur within the bulk of the material - it occurs at the interfaces between crystals (known as grains). Grain ...
13
votes
Melting point of obsidian
Obsidian
This is a volcanic glass, formed when rhyolitic lavas cool too quickly for crystals to form. From a chemistry point of view, it's a mixture of silicon dioxide, aluminium oxide, with sodium ,...
- 231
12
votes
Accepted
How to separate alloys?
You seem to approach the separation of alloys much like the separation of water-soluble salts, probably based on the fact that both involve the liquid/solid phase diagrams, which may even look alike. ...
- 31.2k
11
votes
How do you melt metals with super high melting points?
There are two alternatives to the other answers here, though whether they can be used on a large scale is open to question.
The first is to use an actively cooled vessel to hold the metal and a ...
- 36.1k
11
votes
What easily accessible material has melting point between 500 °C and 590 °C?
Name
Formula
m.p./°C
Copper(II) chloride
$\ce{CuCl2}$
498
Barium perchlorate
$\ce{Ba(ClO4)2}$
505
Potassium fluoroborate*
$\ce{KBF4}$
530
Antimony trisulfide (stibnite)
$\ce{Sb2S3}$
550
Calcium ...
- 28.3k
10
votes
d-Menthol vs dl-menthol: Does an enantiomer and its racemic mixture have different melting points?
In stereochemical vocabulary, a racemic mixture (racemate) is one that has equal amounts (50:50) of left- and right-handed ($d$- and $l$-) enantiomers of a chiral molecule. According to Wikipedia: ...
9
votes
Is it possible to freeze water by dissolving a salt?
It is possible, in a significantly different way that you envision. Freezing point depression via the cryoscopic constant is an example of a colligative property, which holds only for relatively ...
- 28.7k
9
votes
Melting point of aspirin, contradicting sources
The CRC Handbook of Chemistry and Physics ($\mathrm{86^{th} Ed.}$, section on Physical Constants of Organic Compounds) provides an MP of $\pu{135^\circ C}$
for aspirin (2-(Acetyloxy)benzoic acid).
...
- 21.7k
9
votes
Accepted
Can silicon dioxide melt at 20 °C?
Question: Can $\ce{SiO2}$ melt at $\pu{20 ^\circ C}$?
According to experimental and calculated data values, my answer is no. See the phase diagram of pure silica based on the experimental and ...
9
votes
How can steel be so different from iron, even if amount of carbon is small?
Elastic deformation properties like stiffness (Young's Modulus) vary very little with alloying element concentration since we are only working on the pre-yield bond strength. A pure iron, a carbon ...
- 239
9
votes
What easily accessible material has melting point between 500 °C and 590 °C?
There ought to be an alloy with the desired melting point. It doesn't seem to be commercially available, but you could experiment by obtaining tin or zinc, plus copper powder (or scrap brass / bronze),...
- 191
8
votes
Why is the melting point of magnesium oxide higher than aluminium oxide?
Two ideas to consider:
Alumina is not fully ionic. Neither is magnesia, but magnesia has more ionic character and we may see the greatest amount of ionic attraction in magnesia versus alumina which ...
- 57k
8
votes
d-Menthol vs dl-menthol: Does an enantiomer and its racemic mixture have different melting points?
If solid menthol were just amorphous, then you would expect the racemate and each enantiomer to exhibit identical melting points. However, if you read further on the Wikipedia page you reference, you'...
- 700
8
votes
melting and boiling ...really equilibrium?
I think what you are asking is this: Equilibria for chemical reactions typically* (see note at end) require specific ratios of products to reactants (as expressed by the equilibrium constant). By ...
- 12.1k
8
votes
How can steel be so different from iron, even if amount of carbon is small?
Let's consider that steel may contain $\pu{1\%}$ carbon. I know it is a bit much. Let us express this mass concentration as molar concentration for a sample of $\pu{100 g}$ of steel. Since this sample ...
- 28.3k
8
votes
Lower melting points of zinc, cadmium and mercury
Mercury is a rather special case, which cannot be compared to Zn and Cd. Mercury (Z = $80$) belongs to the heaviest elements of the periodic table. Pekka Pyykkö's calculations have shown that nuclei ...
- 28.3k
7
votes
Crystal structure vs melting point
Calcium oxide is double charged, meaning the force required to separate ion pairs is much larger than Sodium chloride.
Melting an ionic solid requires you give an ion sufficient energy to become free ...
- 6,619
7
votes
Why do the melting and boiling points of the noble gases increase when the atomic number increases?
As mentioned in other answers the dispersion force is responsible for noble gases forming liquids. The calculation of the boiling points is now outlined after some general comments about the ...
- 30.4k
7
votes
Why isn't the melting point of H2O very high, if the intermolecular forces are strong?
Melting points of the group 16 hydrides:
Water: 0 °C
Hydrogen sulfide: −82 °C
Hydrogen selenide: −65.73 °C
Hydrogen telluride: −49 °C
Polonium hydride: −35.3 °C
In theory, as the molecules grow ...
- 986
7
votes
Accepted
Why do DMSO and acetone have such radically different melting temperatures?
The first thing to remember is that boiling and melting points, while seemingly simple, are incredibly hard to predict. Yes, many teachers and professors give their pupils and students a number of ...
- 68k
7
votes
Accepted
How can we tell if a salt will melt or decompose?
As noted, chemistry is an experimental science. That being so, experimental data allow for a few rules. Given that salts are often formed from reactions of acids and bases, we should not be ...
- 57k
7
votes
Accepted
The melting and boiling point decreases down the group up to group 14 (not including transition metals), but the trend reverses from group 15. Why?
The problem is, we want to see a trend in everything. There are various factors that govern melting point and boiling point which is the reason of perceived anomalies. "The equation which has ...
- 1,272
7
votes
What easily accessible material has melting point between 500 °C and 590 °C?
As mentioned, various aluminium alloys melt in this range. Alloys and other mixtures don't have a single melting point. They melt over a temperature range between the solidus and liquidus ...
6
votes
Accepted
Are melting points for mixtures of solids ALWAYS below the melting points of the individual components?
Is this always true?
No. As a general rule of thumb, if two compounds are miscible in each other, that is they exhibit solid solution, then the melting point of a (chemical, not mechanical) mixture ...
- 5,274
Only top scored, non community-wiki answers of a minimum length are eligible