The fact that the conductance of some metals rises to infinity at some temperature below a few Kelvin is called

How does the conductivity of metals varies with the rise in their temperature?

The quantity required to increase the temperature of a body by 1 Kelvin is called -

Why does the Conductivity of metals decrease with rise in temperature?

The electrical conductivity of metal decreases with rise in temperature while that of a semiconductor increase . Why ?

The electrical conductivity of a metal decreases with rise in temperature while that of semi-conductor increases. Justify.