Question

Sulphur melts to clear mobile liquid at ${119}^{o}C$, but on further heating to ${160}^{o}C$, it becomes viscous. Explain.

Answer 1

Sulphur melts to clear mobile liquid at $119℃$ and forms Beta-Sulphur which is a yellow solid with a monoclinic crystal form and is less dense than α-sulfur. Like the α- form it contains puckered $S_8$ rings and only differs from it in the way the rings are packed in the crystal. It is unusual because it is only stable above $95.6℃$, below this it converts to α-sulfur.

But on further heating to $160℃$, it becomes viscous because of entanglement of chains.