Elemental silicon exhibits the unusual property that its liquid phase is less dense…
CHEMISTRY · Multi-part · CBSE · Chemistry · The Amazing World of Solutes, Solvents, and Solutions · The Amazing World of Solutes, Solvents, and Solutions
Problem
Elemental silicon exhibits the unusual property that its liquid phase is less dense than its solid phase near the melting point. The following data were obtained at 1410 °C (just above the melting temperature) and 1400 °C (just below the melting temperature).
State | Temperature (°C) | Volume of 50.0 g sample (cm³)
————|———————————|———————————————
Liquid | 1410 | 18.8
Solid | 1400 | 18.1
(a) Determine the density of silicon in both the liquid and solid states at the indicated temperatures.
(b) Which phase is denser under these conditions? Support your conclusion with quantitative evidence.
(c) Provide a particulate-level explanation for why silicon behaves differently from substances whose solids are denser than their liquids.
(d) Predict whether a crystal of solid silicon dropped into molten silicon at 1410 °C will sink, float, or remain suspended. Justify your answer using the densities calculated in part (a) and any relevant intermolecular (interatomic) considerations.