True or false: most conducting materials have different resistances at different temperatures.

The answer is true.

Usually, resistance increases, in case of conductor, with increase in temperature. This occurs because, the valance band and conduction band overlap with each other, so there are excess electrons in the conduction band of a conductor. With the increase of the temperature, more electrons will go to the conduction band from valance band by absorbing the energy. As a result, there will be more collision between the electrons which increases the resistance.