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This question already has an answer here:

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.

Example:

  • for cyanogen, boiling point is -21.2°C while melting point: -27.9°C
  • for propane, boiling point: -42 °C while the melting point: -144°C

Why does this happen?

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marked as duplicate by Mithoron, Tyberius, Avnish Kabaj, Community May 3 '18 at 6:07

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    $\begingroup$ Boiling points and melting points are based on the stability of different phases. There's no reason to assume that the factors that govern the stability of solids governs the stability of liquids in the exact same way and to the exact same degree. $\endgroup$ – Zhe May 2 '18 at 19:30
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well thinking that the same factors influence the melting and boiling point of materials is possibly wrong. high melting point is due to strong packing(highly symmetric molecules) while high boiling point is due to large surface area so if a compound has good packing and less surface area will end up to have very less difference in melting and boiling point and sublime

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