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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Which has a high melting point, cocoa powder or cocoa butter?
I have been doing some research into chocolate, and after looking at the chemical compositions of cocoa butter and cocoa powder, struggled to determine which had a formula/structure that would have a ...
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80 views
Does melting HDPE plastic produce toxic fumes? (melting, not burning)
● The question isn't about burning HDPE but melting it at the proper temperature. (At 120 to 180°C depending on it's density, it becomes gooey. According to the source below the "extrusion" ...
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Question on Melting Points of Group 17,18 and 1
So , I have done some searching and found that melting points of groups 17 and 18 increase going down the group whereas group 1 decreases.
However , the explanation seem to all be the same.
Number ...
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1answer
148 views
Reasons for low melting point of gallium
J.D. Lee writes in Concise Inorganic Chemistry:
Gallium has an unusual structure. Each atom has one closest neighbor at a distance of 2.43 Å.
This remarkable structure tends towards discrete ...
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1answer
147 views
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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Melting point of aspirin, contradicting sources
Querying wolfram alpha for the melting point of aspirin (link) returns $\pu{140 °C}$. The Wikipedia page for Aspirin lists $\pu{136 °C}$ instead, citing this book.
How am I supposed to know which ...
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Melting point in hydrocarbons
Checking out the molecular structure and the melting points of various hydrocarbons I concluded:
1)branching increases the melting point of a hydrocarbon molecule
2)symmetry increases the melting ...
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Is honey really a supersaturated solution? Does heating to un-crystalize redissolve it or melt it?
In the SciShow video Honey: Bacteria's Worst Enemy after about 00:30 the narrator says:
Honey is only about 17% water. Most, but not all of what remains is sugar....
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Is there any sort of correlation between melting point and the degrees of freedom for the molecules of a substance?
Suppose I had a solid whose molecules did not have rotational freedom. But if I were able to make it so that the molecules had rotational freedom ceteris paribus, is there a way to tell how the ...
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1answer
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Is sodium hypochlorite 100% concentrate possible?
Popular bleaching brands like Clorox contain liquid sodium hypochlorite in small concentrations, ranging from 5-12.5% (is this a mass/volume, mass/mass, or volume/volume concentrate?).
Is it possible ...
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Chemical that won't freeze below melting point
I have an organic chemical (can't say due to an NDA) that has a nominal melting point of 28 °C. When I raise it above this temperature, it melts, but then it will stay a liquid indefinitely at lab ...
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147 views
Why does substance that sublime not come to liquid state? [duplicate]
A substance that sublimates doesn't come to a liquid state at room temperature. But when we melt the substance it melts! Why does it skip the liquid state at room temperature?
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Melting point of unsymmetrical dimethylhydrazine vs 1,2-dimethylhydrazine
Unsymmetrical dimethylhydrazine ($\ce{H2NN(CH3)2}$) has a melting point of −57 °C, but its isomer, 1,2-dimethylhydrazine ($\ce{(CH3NH)2}$) has a melting point of −9 °C. That looks to me like a ...
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1answer
70 views
Where can I find reliable data for melting points of organic compounds?
I'm interested in the melting/freezing points of organic compounds, but the online literature has data that's all over the map. I can understand that especially for isomers of alkanes, pure samples ...
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82 views
On what factors do melting and boiling points depend upon?
In my book there is a separate discussion given for trends in melting and boiling points in each chapter in inorganic chemistry (the chapters on the various groups like group 15, group 16, etc.) and ...
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1answer
349 views
Melting point vs Freezing point
Is it possible to have Melting point different that Freezing point
I mean is there any element/molecule in the liquid status that freeze at point X Centigrade but when it become solid then you need a ...
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781 views
Why does the temperature remain constant during freezing?
I know it's the most silly question one could ever ask but why is that so?
I am aware of what latent heat means and I also know it has something to do with freezing too.
Say I have with me, a mug of ...
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1answer
583 views
How does addition of impurities in a solid decrease the melting point? [duplicate]
In my textbook, it is written:
The addition of impurities in a solid decreases the melting point of the solid.
How does it do so? Why can't it increase the melting point?
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Comaparing melting points of group 14 elements [duplicate]
I found that melting point of $\ce{Sn(232°C)}$ is less than $\ce {Pb (327.5°C)} $ but i also saw that the bond enthalpy of $\ce {Sn-Sn(187.1 ±0.3 kJ mol^{-1})}$ is more than $\ce{Pb-Pb 86.6 ±0.8 kJ ...
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Melting of ionic compound hydrates
My professor asked us the reason of the melting point of potash alum being so low, despite it being an ionic salt. He later went on to answer it by saying that melting point is a misnomer for the ...
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Why is the melting point of iodine so high compared to ammonia? What about Zn and C(diamond)? [closed]
Increasing order of melting point by searching the temperature on the web:
$$\ce{NH3} <\ce{I2} <\ce{Zn}<\ce{C_{diamond}}.$$
The idea I have read on "Chemistry: The Central Science" by ...
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Explain the effect of intramolecular hydrogen bonding on solubilities in cold and hot water?
There is a statement given in my textbook (Cengage, Organic Chemistry (Part 1), page 4.33) which is as follows: (I edited the statement to make it simpler)
One can account for the solubilities of ...
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1answer
186 views
Applying salt to roads to melt ice--is it special? [duplicate]
Most everyone is familiar with applying salt to the roads during winter to melt ice.
I'm wondering if there's anything special about placing salt on the roads or would any other substance, sand for ...
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1answer
130 views
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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1answer
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Does the van der Waals force not affect the alkali metal 's trend of decreasing melting points down the table? [duplicate]
Melting and boiling points increase further down the halogen group, but they decrease further down the alkali metal group. I know that the former's trend has to do with the van der Waals force, but I ...
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Phantom Material: why formaldehyde doesn't rise my jelly melting point?
Just to be clear, I'm not a chemical but only a electronic engineer which want create a "phantom material" to reproduce the electrical characteristic of epidermis for the analysis of electrodes ...
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3answers
346 views
Melting point of trans-4-methylhex-4-enoic acid and cis-4-methylhex-4-enoic acid
My book said that the cis isomer has a higher melting point. But I dont understand isn't that the trans isomer can pack more efficiently, because the trans isomer less bulky/ create less 'kink' than ...
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1answer
537 views
Why is the difference between the melting point and boiling point large for some compounds, and small for others? [duplicate]
I was looking at a list of melting and boiling points of various compounds and I realised some had very large differences while some have very less differences between their melting and boiling points....
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1answer
104 views
Predict melting point of water CaCl2 solution
I'm doing a science project for my school. I experimentally measured the melting point of water-salt solutions, and I want to compare my results to theoretical melting points, but I encountered a ...
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How to know if a sample suffered descomposition during melting point? [closed]
If I take a sample in order to determine its melting point, how do I know if that sample suffered a descomposition?
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1answer
2k views
Why does neopentane have a higher melting point than n-pentane?
Why does neopentane have a higher melting point than n-pentane?
I know that we can say that, due to stacking, it has a higher melting point as it freezes easily. But then, why doesn't this happen in ...
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What makes the first 3 alkanes decrease in melting point while after that they rise?
$$
\begin{array}{c|c}
\text{Alkane}&\text{Melting point}\\\hline
\text{Methane}&\pu{-182^\circ C}\\
\text{Ethane}&\pu{-183^\circ C}\\
\text{Propane}&\pu{-188^\circ C}\\
\text{Butane}&...
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1answer
57 views
Which melting point would indicate a metallic structure? [closed]
Question
If you have three substances with three different melting points;
445 °C
1907 °C
-7 °C
Which of these would most likely have a metallic structure?
I understand that the ...
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0answers
224 views
How does the melting point of alkynes change with the position of the triple bond?
$$
\begin{array}{cc}
\text{1-hexyne}&\pu{-132 ^\circ C}\\
\text{2-hexyne}&\pu{-89.5 ^\circ C}\\
\text{3-hexyne}&\pu{-103 ^\circ C}\\
\end{array}
$$
These are the melting points of six ...
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528 views
For two compounds that are symmetrical, why does the more compact one have a higher melting point?
In this post, I refer to two molecules B (Di-tert-butyl ether) and C (Dibutyl ether).
Wikipedia: Di-tert-butyl ether (B)
b.p. 107.2 C
m.p. - 61 C
...
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947 views
If we start heating a substance, does it melt when we break its intermolecular bonds? [closed]
I was reading the 2 following posts:
Do substances melt when we break their intermolecular bonds?
Is melting/boiling point of ionically bonded substance higher than of covalently bound?
Altough ...
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1answer
50 views
What is the reason behind the 2% increase in silver metal composition just after melting the raw silver alloy (55% silver)? [closed]
I determined the silver composition from an alloy obtained from a jeweler to be 55% and wanted to extract silver out of it. However, upon melting around 5 kgs of alloy, the silver composition went up ...
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2answers
194 views
Does granite become soft as modelling clay at 2000 °C?
As Wikipedia tells us, it consists of $\ce{Al2O3}$ ($14.42\%$) (alumina) whose melting point is $\pu{2072^\circ C}$, and $\ce{SiO2}$ ($72.04\%$) (silica) whose melting point is $\pu{1713^\circ C}$. So ...
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2answers
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Melting ice with salt - how does it start?
I know that salt reduces the melting point of ice. I can see how a little bit of salty water can melt ice to water which can dissolve even more salt. But how does it even start? There is ice, which is ...
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Why is the melting point of PCl3 less than that of PCl5?
From just the IB chemistry bonding chapter information, you would normally deduce that $\ce{PCl3}$ and $\ce{PCl5}$ are both covalent molecules.
However, as $\ce{PCl3}$ has a dipole moment, it has ...
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82 views
Near melting thermoplastic material accumulates in the sharper corners. What is this phenomenon?
I have a part made of a thermoplastic material. When I heat it up and cool it down, the dimension of the part changes non-uniformly. Somehow the melted material tries to fill the sharper corners. So ...
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4answers
268 views
Is it possible to freeze water by dissolving a salt?
Theoretically, by dissolving a salt in water the melting point lowers, approximately 1.86 K kg/mol, making it more difficult to freeze water. However, the process of dissolution of certain salts is ...
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Boiling points of HF, HCl, HI [closed]
I'm really confused over how to weigh the molecular mass with intermolecular forces such as hydrogen bonding in HF in terms of figuring out the melting points in relation to each other.
I know that ...
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Suggest why melting point of sodium iodide is lower than the melting point of sodium bromide [duplicate]
I would assume this has something to do with bonding and perhaps density, but I haven't the faintest where I'd begin.
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1answer
161 views
Is molten potassium nitrate possible?
Is it possible to melt potassium nitrate without it decomposing into potassium nitrite and oxygen? If so when it solidifies does it keep its oxidizing properties?
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How do you tell which molecule has a higher melting point?
In the instance of comparing $\ce{NaCl}$, and $\ce{Al2O3}$; which one has a higher melting point and why?
I have learned the following inter molecular forces, however the question the chapter is in ...
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1answer
372 views
How to separate paracetamol and caffeine?
How do you separate paracetamol and caffeine using high-school laboratory equipment?
I was thinking about using the fact that paracetamol has a lower melting point (169 °C) compared to caffeine (...
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1answer
210 views
Chemical reaction between dichloromethane and solid carbon dioxide
I studied heat transfer liquids with low melting point (coolants), and how fast their temperature decreases when they are contacting with solid carbon dioxide. Nearly all liquids (brines, glycols etc.)...
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Why polymers have a range over which they melt instead of having a specific melting temperature? [closed]
Does it have something to do with the fact that all chains are not of the same length?
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Reforging tungsten/tungsten carbide temperatures
I was wondering about the reforging of tungsten and the temperature needed.
As I understand it, tungsten melts at $\pu{3442 ^\circ C}$ and tungsten carbide at $\pu{2870 ^\circ C}$. However, once a ...
