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.  

True: most conducting materials have different resistances at different temperatures

Conducting materials are the objects that permit the flow of electrical currents through them in one or more paths. Common conductors are made from metals e.g. iron and copper. Most conducting materials have different resistances at different temperatures. Resistance is the measure of the difficulty with which an electric current passes through a conductor. The resistance of conducting materials increases with increase in temperature. The conduction band of a conducting material has more electrons. When the temperature is increased, there will be migration of more electrons to the conduction band from valance band. This makes the conduction band to become congested and more collision will occur between the electrons which will then increase the resistance.

enzyme active site and substrate specificity

enzymes bind with chemical reactants called substrates. there may be one or more substrates for each type of enzyme, depending on the particular chemical reaction. in some reactions, a single-reactant substrate is broken down into multiple products