What is Melting point: Definition and 78 Discussions

The melting point (or, rarely, liquefaction point) of a substance is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends on pressure and is usually specified at a standard pressure such as 1 atmosphere or 100 kPa.
When considered as the temperature of the reverse change from liquid to solid, it is referred to as the freezing point or crystallization point. Because of the ability of substances to supercool, the freezing point can easily appear to be below its actual value. When the "characteristic freezing point" of a substance is determined, in fact the actual methodology is almost always "the principle of observing the disappearance rather than the formation of ice, that is, the melting point."

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  1. S

    Melting Point: How Heat Changes Liquids to Solids

    Name a substance that will change from liquid state to solid state on heating.
  2. G

    How to determine which molecule has the highest melting point?

    The question is: Which substance has the highest melting point? (A) CO (B) CO2 (C) SiO2 (D) P2O5 The answer is C but I don't know why (you obviously can't look up the values). I need to be able to figure these types of questions out regardless of the...
  3. S

    PURE compound has higher melting point than the literature?

    What went wrong with the condition or the procedures if I got the melting point of a pure substance to be: (a) lower than the correct mp (b) higher than the correct mp (c) broad in melting range I guess there's something to do with the pressure and wrong calibration, but I don't know what...
  4. P

    Decrease in Aspirin Melting Point

    Homework Statement A student performed the reaction in this experiment using a water bath of 90 degrees C instead of 50 degrees C. The final product was tested for the presence of phenols with ferric chloride. This test was negative (no color observed); however, the melting point of the dry...
  5. Z

    Boiling Point before Melting Point?

    How can an element boil before it melts? I came across this- As - Melting Point 816 C and Boiling Point 615 C. Every other element given along with this element in my book has its melting point lower than boiling point which makes sense to me. I am curious to know what is different about As...
  6. P

    Calculate melting point of ice under pressure

    Homework Statement The density of solid water is approximately 920 kg m^-3 and that of liquid water is 1000 kg m^-3. Calculate the melting point of ice under a pressure of 6000 kPa. Homework Equations This is my problem. How do I approach this? I don't see any relevant equations in my...
  7. P

    How to lower melting point of solids (TiO2)?

    Hi, I'm currently doing experiments on a 99.9% TiO2 source powder. I was wondering if there is anyway to lower the melting point of this solid? If possible, without compromising its purity. I only have access to an electrical furnace that is capable of reaching a maximum of 1200 degC...
  8. S

    Caffeine sublimation and melting point

    Why caffeine has 178 oC as point of sublimation but 237 oC as melting point? Is it about the pressure? If so, then what is the preesure that makes 237 as melting point instead of sublimation at 178 oC? Cuz the science websites always just said 237 is the melting point, but didn't mention the...
  9. S

    About state of matter and melting point

    Homework Statement Hi all I have conceptual problems : 1. In cold countries, water in pipe lines freezes in winter season. Freezing causes volumetric expansion and may burst the pipes. My question :why freezing causes volumetric expansion? 2. Mostly, substance increases their...
  10. T

    Cause of melting point depression

    Homework Statement An unknown compound gave a melting point of 230C. When the molten liquid solidified the melting point was determined to be 131C. Give a possible explanation for this discrepancy. Homework Equations The Attempt at a Solution I understand that melting point...
  11. G

    Which Solid Has the Highest Melting Point?

    Homework Statement hey guys, just wondering if you could tell me which of these is polar and how to do it thanks? the question is asking for the highest melting point, so i believe it relates to which is polar. any help would be greatly appreciated. Homework Equations Which of the...
  12. M

    Dirty snow (snirt) & melting point

    You know that dirty disgusting snow that accumulates on sides of roads over the winter, and then doesn't melt until well into May or something? Why is it that this snow refuses to melt? It mixes with dirt and exhaust fumes from the cars, and somehow becomes really hard and un-meltable. Does...
  13. N

    Increasing the Melting Point via Pressure Increase

    1. What is the pressure needed to increase the melting temperature by 20 centigrade degrees? Given: Molar Volume (solid) at normal melting temp is 18.92 cm^3 Given: Molar Volume (liquid) at normal melting temp is 19.47 cm^3 Homework Equations delta H (s>l) = T(melting point)* delta S(s>l)...
  14. J

    Melting point and solubility in water of benzoic acid

    in literature, find melting point and solubility in water of benzoic acid, vanillin, phthalic acid, salicyclic acids. Calculate the expected volume of hot water that would be requried to dissolve 0.15g of each compound. With info on melting point and solubility in water... how can you...
  15. E

    Why does melting point decrease for impure solid?

    Okay, i am doing a lab involving crude acetaminophen and pure acetaminophen. The crude acetaminophen is supposed to have a lower melting point than the pure acetaminophen... how does that work and why? does it have to do with thermodynamics or what??
  16. K

    Finding the Highest Melting Point

    If you have a question such as "Which substance has the highest melting point?" & say these are the substances CH4, HF, He, CL2, how would you determine an answer? I'm not really looking for an answer to this particular question, but in general, there must be something I've forgotten in my...
  17. G

    Applicatino of Raoults Law and melting point

    Homework Statement What is the effect of an insoluble impurity such as sodium sulfate, on the observed melting point of a impure compound? Homework Equations The Attempt at a Solution My answer is, there is no effect on the melting point of this particular compound. Because it...
  18. P

    Which Structure Has The Highest Melting Point?

    Which structure will have the highest melting point?
  19. J

    What happens to lead then you overhead it beyond its melting point

    What happens to lead then you overheat it beyond its melting point, and what metal or chemical does it become then?
  20. J

    How to change the melting point of a metal?

    How to change the melting point of a metal? Like example: Iron melting point: 1535 °C Sulfur melting point: 115.36 °C If you combine Iron and Sulfur in a airtight container and light a monster fire under it, you get a sort of a pyrite (iron disulfide (FeS2)– Melting point 1,177-1,188 °C...
  21. M

    How Does Increasing Pressure Affect the Melting Point of Solids?

    How would I show that the melting point of a solid decreases with increasing pressure knowing that the specific volume of the liquid is less than the solid? dP/dT=delta h / (T delta v) Clapeyron equation Inverse it: dT/dP = (T delta v)/delta h v" < v' : molar volume vapor < mol. volume...
  22. M

    Glass Melting Point: Why & Are Glasses Liquid?

    Why Do Glasses Doesnt Have A Melting Point? And Are Glasses Liquid?thanks
  23. J

    Melting Point of three compounds

    Does anyone have or know where I can find literature values for the melting points (or melting ranges) of the following three semicarbazone compounds? 4-Methoxybenzaldehyde semicarbazone Isopropylbenzaldehyde semicarbazone Carvone semicarbazone (either the R or S diasteriomers) I haven't been...
  24. S

    What's the melting point of a person?

    Just thinking about those stories you hear about dresden and tokyo. The ones about people being melted alive in bunkers. Exactly what conditions would have to exist for that to be possible?
  25. A

    Explaining the High Melting Point of Water

    Hi.. I've finished this topic but I was confused in this question. The question is : The main reason for the high melting point of water compared to other group4 hydrides can be explained by: a.Ionic Bonding b.Covalent Bonding c.Dispersion Forces d.Hydrogen Bonding I'm not sure...
  26. P

    Uncovering the Mystery of Acetanilide and Caffeine Melting Point Range

    I have a sample of 25 % acetanilide with 75 % caffeine. I record a melting point range of 198 - 240 degrees celcius acetanilide's melting point is 114.3 caffeine's melting point is 238 What would cause this huge experimental range? My thinking is that the acetanilide is...
  27. M

    Hypereutectic melting point

    [Originally posted to material science forum but no reply] It's no surprise that if I take a particular metal and 'add' atoms of a second metal that has a lower melting point that the Tmelt of the combination is usually lower than that of the pure metal. This is hypoeutectic composition...
  28. Monique

    Melting point of 40% Sn and 60% Pb

    Who can calculate the meltingpoint for me of a mixture of metals with 40% Sn and 60% Pb?
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