Two crystalline substances, sodium chloride (NaCl) and sucrose (C12H22O11), are each placed in separate crucibles and gradually heated. After melting points are reached, fresh samples of each substance are dissolved in distilled water and the resulting aqueous solutions are tested for electrical conductivity using identical conductivity meters.
(a) Identify which solid—NaCl or sucrose—has the higher melting point, and provide a chemical explanation based on the nature of the particles and forces present in the solid phase.
(b) Neither NaCl nor sucrose conducts electricity in the solid state, yet their aqueous solutions behave differently when the probe is inserted. Explain the difference in conductivity between the two aqueous solutions, citing the types of species present in each solution and their mobility.
(c) In terms of lattice structure and particle interactions, explain why NaCl crystals are brittle whereas sucrose crystals can be cut relatively cleanly with a sharp blade without shattering.