Questions tagged [melting-point]

The melting point of a solid is the temperature at which it changes state from solid to liquid.

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1answer
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Melting and boiling point trend in Group II

The following picture shows the melting and boiling point trends down group II elements. I have added question marks where the variability in data was rather disturbing (over two hundred degrees ...
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How can we tell if a salt will melt or decompose?

Take $\rm NaCl$ for instance, a salt that will melt when it reaches its melting point, and compare it with $\rm NH_4NO_3$, a salt that doesn't melt, but instead decomposes to $\rm N_2O$ and $\rm H_2O$ ...
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Is there a material that reduces copper melting point and completely dissolves?

Is there any material that you mix/alloy with copper that will result in something that behaves similar to plastic (that is at room temperature it is solid, at maybe 500K or similar it can be easily ...
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Why are the melting and boiling points of the group 1 metals lower than the group 2 metals in the same period?

I thought it was because the group 1 metals are smaller than the group 2 metals but the answer sheet says it's because there are more valence electrons and a stronger positive charge in group 2 metals....
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Methanol-water mix freezing points - clarify contradictory online data > 60% w/w?

Extending an exploration of windshield washer-fluid choices to freezing points of methanol-water mixes, all web-sources located agreed to within a couple of degrees from 0-60% w/w, yet above this ...
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Why do the boiling and melting points decrease as you go down group 1 and vice versa for group 7?

I used to think that because an alkali metal needs to lose one electron to complete its outer shell, when the atom increases in size (atomic radius), the electron would be easier to lose as the ...
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Why is the melting point of magnesium nitride less than that of beryllium nitride?

Why is melting point of $\ce{Mg3N2}$ lower than that of $\ce{Be3N2}$ ? I have two reasonings: The lattice energy of $\ce{Be3N2}$ is higher than that of $\ce{Mg3N2}$ so accordingly the melting point ...
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Why is there no exothermic crystallization peak visible during cooling of PLA and no endothermic melting peak visible during a second heating of PLA?

I am doing lab research on DSC measurement (Heat-cool-heat) for understanding melting characteristics of polymers (PLA, PA6 and PE). During cooling i saw exothermic peak and during second heating i ...
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How do you melt metals with super high melting points?

At the Renaissance fair a few years back I was watching a smith forge metal into shapes. During this time a very odd question came to me. I was wondering what the furnace was made of. My logic stated ...
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Hydrates and melting points

Basalt melting point: wet vs dry I had a student ask me this in class the other day; I thought about it, but I still can't work it out. Many mineral and rock hydrates (take basalt, for instance) ...
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What happens if you superheat timber in a zero oxygen environment? [duplicate]

I was thinking to myself, what would happen if you were to put a lump of wood in a zero oxygen environment and superheat it? It couldn’t burn because fire needs fuel, heat and oxygen however because ...
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Caffeine boiling and melting points

According to both caffeine's PubChem page and ChemSpider page its boiling point lies at $\pu{173 °C}$ and its melting point at $\pu{\sim 235 °C}.$ How can it melt at that temperature if it already ...
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Comparing of melting point of dibromo p-xylenes

How to compare the melting points of the above isomers? I know that melting point depends upon the packing of the molecule, more efficient the packing, higher is the melting point. Symmetry in a ...
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Can you melt wood?

We talked about it in our chemistry class but we couldn't get to a conclusion, any help?
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What effect on boiling and melting points does intramolecular hydrogen bonding have? [duplicate]

I know that intermolecular forces increase the boiling and melting point of a compound, but what is the effect of intramolecular forces on boiling and melting points? I found contradicting answers ...
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Why are highly branched alcohols solid?

Usually branching (or decrease in surface area) leads to increased volatility. But in case of alcohols, my book states that: The higher alcohols (butanols to decanols) are somewhat viscous, and ...
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Compound with pressure sensitive melting point at moderate temperature and pressure

I'm in need for a compound with ideally all of the following properties: A melting point of 5 °C or less at 1 atmosphere (or slightly lower pressure) A melting point of 12 °C or more at less than 20 ...
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Crucible design for melting alumina

I'd like to melt alumina in a slow, controlled manner. So I thought a graphite crucible with a tungsten wire wrapped around it for heating would be a good start. To reduce heat losses, I put that ...
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1answer
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Melting points of benzoic and stearic acids

I wonder, why does benzoic acid have a higher melting point than stearic acid? Here is the data: Benzoic acid melting point = 122.3 °C Stearic acid melting point = 69.3 °C I do understand that organic ...
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At what temperature does charcoal burn?

According to some sources, charcoal burns at temperatures as high as 2600 °C (Wikipedia), others (that seem less reliable) say around 1000 °C. I know that it depends on the air flow, but how high of ...
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How to calculate which ionic compound has the highest melting point?

Which of the following compounds has the highest melting point: $\ce{PCl5}$, $\ce{H2O}$, $\ce{NaCl}$, $\ce{SrCl2}$, $\ce{CaF2}$? In general, ionic compounds will have higher boiling points than those ...
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Judging orders in a series of compounds

My teacher frequently gives us questions where we have to arrange the given binary compounds on basis of their melting points or solubilities. He did give us some instructions in order to judge this ...
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ethanol/water %vol/vol and freezing temperature

Main Question: Where can I find a table (or realistic formula) for isopropanol/water %vol/vol mixes and corresponding freezing temperature with public access? Background: Trying to get the freezing ...
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Why are the melting points of Sb and Bi lower than that of As?

My book says it has something to do with the inert pair effect. And unlike As, Sb and Bi tend to form 3 covalent bonds rather than 5. I don't understand what's really going on here.
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Why is the melting point of magnesium oxide higher than aluminium oxide?

There's a graph of the melting points of period three oxides. The melting point of magnesium oxide is several hundred Kelvin higher than aluminiumoxide. I can't find any explanations for this on the ...
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Change in boiling and freezing point

I recently encountered a question while solving previous year question papers for JEE. This is a JEE 2005 question. The question demands to complete this statement: Equimolar solutions in the ...
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Why is melting point of Vanadium higher than Iron? [duplicate]

The iron is found to have four unpaired electrons while vanadium has 3 of them. we say the binding energy is directly proportional to number of unpaired electrons and hence number of metallic bonds ...
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Why does diethylmethylamine have such a low melting point?

According to PubChem, diethylmethylamine has a remarkably low melting point of $-196.0\ \mathrm{^\circ C}$. This is substantially lower than the melting points of dimethylethylamine ($-140.0\ \mathrm{^...
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Why the melting point increase up to arsenic and then decrease down the group 16? [duplicate]

I am already google this but can't find the answer that staisfy me. I know down the group, mass and atomic size increase which result in increase in van-der-waal forces. But in group 16 the trend is ...
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Melting point of objects and food

What is the melting point of egg yolk? Well, generally, when we break an egg, the yolk is in liquid state. After we pour it on a pan, the egg starts to cook and it hardens. My question is, can an egg ...
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Effect of impurities on melting point

This is a 10th-grade question. The melting point of a substance decreases with increase in presence of impurities in it. The melting point of ice decreases from 0 °C to -22 °C on mixing salt in it ...
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Why is brine solution more effective than granular salt in melting ice on a surface?

Why is a brine solution consisting of a small fraction of salt in water, more effective in melting ice on a surface, than just pure salt?
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Comparing melting points of substituted benzaldehydes

The correct decreasing order of melting point for the given organic compounds is: 3 has maximum melting point because of intermolecular hydrogen bonding. I am unable to predict rest of the order ...
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Why do the melting points of Group 15 elements increase upto Arsenic but then decrease upto Bismuth?

The boiling points of group 15 elements increase on going down the group (or, as size increases) but the same is not true for the melting points. The melting points increase from $\ce{N}$ to $\ce{As}$ ...
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Can silicon dioxide melt at 20 °C?

Can $\ce{SiO2}$ melt at $\pu{20 ^\circ C}$? I have searched the web for $\ce{SiO2}$ phase diagram, but it seems to me that almost all the graph I can find have the temperature axis where the minimum ...
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Why is the melting point of p-dichlorobenzene higher than those of o-dichlorobenzene and m-dichlorobenzene?

I was going through alkyl and aryl halides and noted the following statement in my textbook: p-dichlorobenzene has higher melting point and solubility than those of o-dichlorobenzene and m-...
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Why does magnesium have an exceptionally low melting point?

Why does magnesium have a lower melting point than both calcium and beryllium? It does not seem to fit into the group trend.
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Melting and boiling points of benzene and fluorobenzene

This species is a derivative of benzene, with a single fluorine atom attached. Its melting point is -44 °C, which is lower than that of benzene, indicative of the remarkable effect of fluorination ...
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d-Menthol vs dl-menthol: Does an enantiomer and its racemic mixture have different melting points?

I am checking out Wikipedia and it shows a different melting point (m.p.) for l-menthol $(\pu{42 ^\circ C}$ to $\pu{45 ^\circ C})$ vs dl-menthol $(\pu{36 ^\circ C}$ to $\pu{38 ^\circ C}).$ How is ...
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Can Aluminum Hydroxide (Al(OH)3) be heated to it's melting temperature before decomposing?

On the wikipedia page for aluminum hydroxide the listed melting point is 300 °C (572 °F), but in the same page it states that aluminum hydroxide decomposes at only 180 °C (356 °F). Can aluminum ...
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Why does aluminum chloride have a higher lattice energy than aluminum fluoride?

From the table below (source: McMurry's Chemistry [1, p. 212]), it is evident that $\ce{AlCl_3}$ has a higher lattice energy than $\ce{AlF3},$ even though $\ce{F}$ is smaller than $\ce{Cl}$. Why is ...
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1answer
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Clausius–Clapeyron equation: shape of phase diagrams makes no sense

I am trying to model the melting point of a substance at varying pressures (ranging from very small to very very large). All I am trying to do is make an equation that relates melting temperature to ...
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How to separate alloys?

How do you separate metal alloys into their constituent elements, especially industrially? I don't think you can always use melting points, because alloys, depending on the composition (looking at ...
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Is there a correlation between the susceptibility of a polymer to undergo hydrolysis and its melting point?

As per topic, I was wondering why the Tm of the polymers PGA, PLA and PLGA are in the following order. Does it correlate to their ability to undergo hydrolysis? PGA>PLA>PLGA
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Why alkanes containing even number of carbons can be packed more efficiently than alkanes with odd number of carbon atoms?

Variation of boiling and melting points of alkanes with increase in the number of carbons The odd-numbered alkanes have a lower trend in melting points than even numbered alkanes. This is because ...
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Melting point of crystalline solids

Why crystalline solids have sharp melting points but melting point of amorphous solids vary within a range? Is it because the interaction energy is equal between atoms of crystalline solids so they ...
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Covalent Bonds and Ionic Bonds [duplicate]

Covalent bond is a strong bond compared to Ionic Bonds but Ionic Compounds have higher melting and boiling points then covalent compounds. Why?
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Why don’t all objects melt and liquefy when heated sufficiently?

Certain objects such as metals, glass, plastic, sugar etc. melt when heated to a certain temperature but other materials such as a piece of wood, paper, a piece of rock etc. do not. Why is that?
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The effect of air pressure on the melting point

What is the effect of air pressure on the melting point of a substance? a) No effect b) The melting point increases when the air pressure increases c) The melting point decreases when the air pressure ...
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Mechanistic explanation of salt lowering temperature of ice slush

As we all know, adding salt to ice water lowers its temperature. I've read plenty of system-level accounts of energy balances, enthalpies, vapor pressures, phase equilibria and freezing points—I ...

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