How Does Melting Affect the Polarizability and Dielectric Constant of a Medium?

[Joseph Phan]

I understand that as a solid melts, it increases can increase in polarizability of the medium, and increase the Dielectric constant (K).
-ex. like dissolving NaCl and having ions in solution.

Why does Thermal motion reduce the polarizability of the medium, thus decreasing the dielectric constant?
Is it because when a strongly polar medium respond to an external electric field, the medium reorienting its polar molecules so that the net electric field within the medium becomes weaker than the external field?

 

[Paul Colby]

When a field is applied to a dielectric the composite dipoles align so as to reduce their potential energy. Thermal agitation will on average raise the dipole energy decreasing the net polarization or alignment.