Explain why the electrolytic cell containing Lead Bromide needs to be heated before electrolysis can occur.

Electrolysis means the splitting apart (“lysis”) of a compound through application of electrical voltage. In this case, we want to electrolyze lead (II) bromide. This is an ionic compound, so the elements are present as ions: lead with a charge of +2, and bromine with a charge of -1. In the pure elements, however, the atoms are neutral. The application of electricity provides two electrons to each lead ion and removes one electron from each bromide ion, making both neutral. We get solid lead metal and Br2 gas (although Br2 is a liquid at room temperature, this reaction needs to be heated).
Reduction of lead ions occurs at the cathode, while oxidation of bromide ions occurs at the anode. The ions must be able to migrate to the appropriate electrodes for this to occur. Another way we often express this is to say the circuit must be complete in order for electric current to flow. Because the cathode and anode are physically separated in the PbBr2, current needs to be conducted through the compound. Current can flow only if something with a charge is able to move. The ions have charges, but in solid PbBr2, they are held rigidly in place. In melted ionic compounds, however, the ions move about freely, so we must heat the lead (II) bromide to melt it in order for electrolysis to occur.