CHEMISTRY · Multi-part · AP · Chemistry · Compound Structure and Properties · Compound Structure and Properties
Problem
An unknown white crystalline solid, labeled "Substance X," is suspected to be either a molecular solid, an ionic solid, or a metallic solid. You are provided only 2.0 g of the solid and access to standard laboratory equipment capable of performing the following measurements:
• Melting point determination (up to 1500 °C)
• Electrical conductivity of solid samples
• Electrical conductivity of liquids at temperatures up to 1500 °C
Design and justify an experimental plan that will allow you to determine which of the three categories best describes Substance X. Your plan must conserve material and yield conclusive evidence.
(a) Outline the sequence of experimental steps you would perform, including the data you would collect at each stage.
(b) For each possible outcome of your tests, state the interpretation that would lead you to classify Substance X as molecular, ionic, or metallic.
(c) Explain, at the particulate level, why the measurements you selected in part (a) effectively distinguish among the three types of solids.
(d) Identify one limitation or potential source of error in your procedure and propose a method to mitigate it.