Video Transcript
In which of the following scenarios is an ionic substance conductive? (A) When it is broken into very small pieces. (B) When it is freshly made. (C) When it contains a mixture of different ions. (D) When it is molten. Or (E) when it is cooled with liquid nitrogen.
To answer this question, we must know under what circumstances an ionic substance would be conductive or, in other words, when an ionic compound would be able to conduct electricity by permitting electric charge to flow. Charge can flow in the form of ions or unbound electrons. Ionic substances are ionic compounds that are held together by the attractive forces between negatively and positively charged ions. Through the formation of ionic bonds, ionic lattices are formed. These lattices are the main structure of the solid form of ionic compounds.
An ionic lattice is a giant three-dimensional structure that is made up of oppositely charged ions. Positively and negatively charged particles are not mobile when they are trapped in the giant three-dimensional lattice. However, if the ionic lattice is melted to its liquid state or dissolved in water, the lattice becomes disconnected and is no longer structured in an organized fashion. Therefore, the ions become mobile and are able to carry an electric charge and thus conduct electricity. So while ionic compounds do not conduct electricity when they are solid, they can conduct electricity when they are melted or dissolved in water.
Since the term molten means melted or in its liquid state, the scenario in which an ionic substance is conductive is answer choice (D), when it is molten.