Questions tagged [melting-point]

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

Filter by
Sorted by
Tagged with
12
votes
1answer
3k views

Why is the melting point of tert-butyl alcohol 140 °C higher than that of sec-butyl alcohol?

This is one of the most drastic differences in a physical property I've ever seen for two such similar molecules, and in a simplistic sense anyway the difference lies in the opposite direction from ...
2
votes
1answer
181 views

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?
0
votes
0answers
2k views

Why magnesium has the lowest melting and boiling point in its group? [duplicate]

It is written in the third point ( shown in the picture) that presence of d orbitals results in stronger metallic bond. 1) We check the strength of metallic bonding to compare the melting and boiling ...
0
votes
1answer
427 views

Why is the melting point of lactic acid higher than pyruvic acid

I have a quick question about pyruvic acid and lactic acid, which I think I know the answer too but I'm unsure. The melting point of lactic acid is said to be higher than that of pyruvic acid ...
3
votes
1answer
6k views

At the freezing point, why is the vapor pressure of the liquid phase equal to the vapor pressure of the solid phase?

At the freezing point of a substance, the solid phase is in dynamic equilibrium with the liquid phase. My textbook defines the freezing point of a substance as: "the temperature at which the vapor ...
4
votes
1answer
127 views

What kind of string to use for the ice fishing experiment for kids?

Classic ice fishing experiment for kids. I used nylon because I saw it in a stationery, and apparently that doesn't work because I guess it's too slippery. I tried thread from my mom's sewing kit, ...
3
votes
0answers
2k views

How can a substance have a higher boiling point but lower melting point than another substance?

Looking at 1,3-Butadiene and Isoprene, I'm wondering: why does Isoprene have a higher boiling point, but a lower melting point than 1,3-Butadiene? I'm thinking this might be because the Methyl group ...
4
votes
2answers
7k views

Why is the melting point of hydrogen iodide larger than that of hydrogen fluoride?

Compare the melting points of hydrogen fluoride (HF) and hydrogen iodide (HI). I know the following things: $\ce{HF}$ melts at $189.6~\mathrm{K}$ and $\ce{HI}$ at $222.35~\mathrm{K}$. There are a ...
1
vote
1answer
106 views

Can every chemical compound be melted?

Are there any chemical compounds that disintegrate (without going into other chemical reactions; let's say in a vacuum) before reaching a melting temperature?
2
votes
1answer
3k views

Why do DMSO and acetone have such radically different melting temperatures?

DMSO and acetone have almost identical structures, except for us replacing the carbonyl carbon with sulfur to obtain DMSO. DMSO's melting point is $19~\mathrm{^\circ C}$, whereas acetone's is $-95\ \...
1
vote
2answers
3k views

Is it possible to melt a diamond? [duplicate]

I am school student. In my school text book there is a fact about diamond. That is Each carbon atom is covalently bonded to four other carbon atoms. A lot of energy is needed to separate the atoms ...
0
votes
1answer
5k views

Melting Point Trend For Non Metals?

I noticed that the melting point for non metals decreases across a period (i.e. melting point of nitrogen is higher than oxygen, oxygen's is higher than fluorine, so on). It is significantly more ...
0
votes
1answer
271 views

Validating Phase Diagram of a mixture

In lab I did several different runs to create a phase diagram for the mixture between biphenyl and naphthalene. My phase diagram is attached, just for visual purposes. My question is I'm supposed to ...
-2
votes
1answer
385 views

Melting Lithium foil to make ingot?

I'm not sure of this is the correct spot for this but I am curious about this. I want to make some Lithium ingots. The only source of Lithium I have is the foil from Lithium batteries. My question is ...
5
votes
1answer
2k views

Comparison of alkali and alkaline earth melting points - MO theory

If you compare the melting points of alkali and alkaline earth metals, you see that the latter have higher melting points. However, if you look at MO theory, then alkaline earth metals should have ...
4
votes
1answer
125 views

Melting post-1982 minted U.S. pennies and aluminum: Why does the slag turn blue?

After melting aluminum inside of an iron crucible, I tossed in a handful of U.S. pennies that were minted post-1982. The slag began to burn a brilliant blue. What caused this?
8
votes
1answer
13k views

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 ...
1
vote
3answers
2k views

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?
2
votes
1answer
229 views

Nucleation and Phase Equilibrium at the Melting Temperature

I used to think that at the melting point, the solid and liquid phases are in equilibrium. That’s because the Gibbs free energy change for the transformation is 0, as is characteristic of equilibria. ...
5
votes
3answers
67k views

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 ...
-1
votes
1answer
1k views

Trends in the melting points of alcohols, aldehydes and ketones

Is there a general trend in the melting points of alcohols, aldehydes and ketones? Usually with the boiling point, it increases as the number of hydrocarbons increase, but what happens in the case of ...
1
vote
1answer
2k views

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....
-1
votes
2answers
1k views

Do we cool the solution to form a precipitate because of lower melting points?

If we have two compounds in aqueous solution, in order to separate one from the other the solution is placed into an ice bath. For example the formation of $\ce{KClO3}$ from a combination of $\ce{...
6
votes
0answers
8k views

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 ...
2
votes
2answers
1k views

Why does calcium chloride cause a greater freezing point depression in water than magnesium chloride?

So I saw this equation for the freezing point depression, when you add a solute: $\Delta T= K_\mathrm fmi$ Where, $\Delta T =$ The freezing point depression $K_\mathrm f =$ The freezing point ...
1
vote
1answer
2k views

Why is the melting point of KBr higher than that of CsCl?

I thought that when compounds have similar forces and charges, the one with the higher molecular weight has the higher melting point. If that is true, then why is the melting point of $\ce{KBr}$ ...
3
votes
1answer
3k views

When SiO2 changes state, what forces/bonds are being overcome/broken?

When silicon dioxide changes state, are the covalent bonds being broken (ie. the intramolecular forces) or is it the intermolecular forces?
0
votes
3answers
1k views

Which isomers of C6H4(OH)2 has a higher melting point?why?

At first I thought that the first isomer must have the highest melting point since it's the most polarized isomer. So I looked them up on Pubchem to be sure and the answer was exactly the opposite;the ...
2
votes
2answers
17k views

Are melting points for mixtures of solids ALWAYS below the melting points of the individual components?

In every chemistry lab we are taught that mixtures of compounds are going to have melting points lower than either of the components pure melting points. Is this always true? Or can there be ratios ...
-1
votes
1answer
3k views

Why isn't the melting point of H2O very high, if the intermolecular forces are strong?

H2O has very strong intermolecular forces due to the hydrogen bonds that a formed within the compound. Usually this would mean the compound has a very high melting point as a large amount of heat ...
6
votes
2answers
540 views

How could uranium be extracted from ore to be melt?

I would like to go hunting for uranium ore, and because it has a relatively low melting point (1132.2 °C), I thought it would be cool to melt it just like any other metals. According to this video ...
2
votes
1answer
1k views

Melting point of ocean salt: eutectic?

I'm interested in the melting point of ocean salt. While sodium chloride has a melting point of 801 °C, ocean salt contains 15 % other ions, mainly sulphate, magnesium, calcium and potassium (the ...
0
votes
1answer
13k views

Melting points of alkali metal halides

The correct order of melting point of alkali metal halides is: $\ce{MF}>\ce{MCl}>\ce{MBr}>\ce{MI}$ $\ce{MI}>\ce{MBr}>\ce{MCl}>\ce{MF}$ $\ce{MCl}>\ce{MF}>\ce{MBr}>\ce{MI}$ $\...
30
votes
1answer
14k views

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 ...
1
vote
1answer
72 views

Manipulate melting point of frozen water [duplicate]

How to manipulate water in way that ice melting point isn't 0°C, but for example 4°C?
3
votes
0answers
4k views

Intermolecular Forces in Teflon vs Polyethylene

From Wikipedia, polyethylene has a melting point of around $400K$, while Teflon (polytetrafluoroethylene) has a melting point of $600 K$, which is much higher. Besides the increased London Dispersion ...
1
vote
2answers
7k views

Assumptions made in calculating melting point from thermodynamic data

I'm fine with doing these questions, such as: For ammonia, enthalpy of fusion is 5.65 kJ/mol, and entropy of fusion is 28.9 J/K.mol Hence find an approximate melting point: Well $\Delta G = \Delta H ...
7
votes
1answer
2k views

Crystal structure vs melting point

Calcium oxide has a melting point of $\ce{2700^\circ C}$ and sodium chloride has a melting point of $\pu{801^\circ C}$. If they have the same crystal structure and ions are about the same distance ...
1
vote
0answers
29 views

Melting temperature and electronegativity trends in transition metals [duplicate]

So I know that generally the melting temperature increases across the row (let's look at just the first row for now) but what are the deviations? And why do they occur? I've looked everywhere online ...
7
votes
2answers
6k views

Liquifying metal and toxic fume exposure

I just read a very entertaining Youtube comment thread on a video where TheBackyardScientist melts tin on the stove in his (enclosed) kitchen, the proceeds to cook a steak on it. According to the ...
1
vote
0answers
680 views

What is the melting point of glycerol in a vacuum?

Can anyone tell me what the melting point of glycerin would be in a vacuum? From researching online (disclaimer: I'm definitely not a chemist) it seems the boiling point is $\approx \pu{170^\circ C}$ ...
0
votes
1answer
895 views

Melting point-general chemistry

This one has stumped me for a few days. What is the specific name of the general chemistry principle that is responsible for the difference in melting points of pure and impure solids. I have ...
5
votes
1answer
1k views

How does ice melt?

I know that when water freezes, it forms a crystalline structure created by the hydrogen bonds between polar water molecules. Also, I know that during a phase change, the potential energy of the ...
1
vote
1answer
205 views

Would a melted crystal recrystallize back into the same lattice structure when frozen?

Two things that I'm not sure about melted crystals: For a material that has only one possible crystal structure, would freezing cause it to recrystallize, or could it become amorphous upon freezing? ...
6
votes
3answers
14k views

How can sodium chloride melt ice or keep it frozen?

In European countries, they use $\ce{NaCl}$ or $\ce{KCl}$ to melt ice during the winter season. In Asian Countries, they use $\ce{NaCl}$ to keep the ice without melting, for example in ice cream and ...
3
votes
0answers
73 views

Is it possible, given a target temperature, to create an alloy that melts at precisely that temperature?

Assuming the target melting points are between the melting points of mercury and tungsten, is it possible, given a target temperature, to create an alloy (or compound) composition that has a direct (...
7
votes
1answer
27k views

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 ...
3
votes
2answers
2k views

At what temperature (in kelvin) are most of the elements on the periodic table liquids?

This question is out of pure curiosity. At what temperature are a majority of the elements on the periodic table in a liquid state/phase of matter? For the purpose of this question, assume the ...
0
votes
1answer
752 views

How to create liquid carbon, and what kinds of properties does it have? [duplicate]

Carbon sublimes at about 3915K. In a high pressure environment, shouldn't it be possible to create liquid carbon at high temperatures? Has this ever been done? What does it look like and what ...
0
votes
1answer
152 views

Why there is a non-linear trend on the melting points for period 2 elements, especially Na to Si?

Using the knowledge of periodicity from high school cannot explain this, what it tells me is just metallic bonding. The model of delocalised electron from a metallic lattice can explain the increase ...