Does inductance vary over frequency in passive components. Consider a Coax cable for example, does the inductance value change as a function of frequency, lets say from 5GHz to 100GHz, does the inductance value ever change?
Yes, for just about any practical component, the effective inductance will change with frequency.
A coaxial cable is not an easy example to deal with. You should rather be considering it as a transmission line rather than a lumped inductor or inductor/capacitor network. So I'll leave that aside.
Instead consider an inductive coil. Any real coil has interwinding capacitance, caused by electric field between adjacent coils of the inductor, and modeled (in a simplified way) as a capacitor in parallel with the idealized inducutor. Above some frequency, the interwinding capacitance will tend to dominate the behavior of the device, causing the reactance to be negative and decreasing with frequency rather than positive and increasing.
Similarly, practical capacitors nearly always have lead inductance. This acts as an inductor in series with the idealized capacitor. Above some frequency (often specified as series resonance frequency in capacitor datasheets), the lead inductance tends to dominate the device behavior resulting in positive reactance increasing with frequency rather than negative and decreasing.
The frequencies where these effects become important range from kilohertz to gigahertz depending on the device construction, and you will want to be aware of them when choosing components in your designs.
Furthermore, even if you neglect these geometrical parasitic effects, you'll find that the critcial parameters (permeability of inductor cores and permittivity of capacitor dielectrics) also vary over frequency due to the resonances of the molecules producing the magnetization or polarization that determines those quantities. This will cause the inductance or capacitance of the device to vary (at least slightly) with frequency.