Chapter 13, Problem 52A

Interpretation Introduction

Interpretation: Changes happening when a solid is heated to its melting point are to be explained.

Concept introduction:

At the melting point, a liquid is now forming from the solid. Although the liquid's particles are identical to those in the solid, they are more energetic. Energy must be used to overcome the interactions between the particles in a solid to allow them to be pulled apart and melt the solid.

Answer to Problem 52A

Molecular solids are held together by weak van der Waals forces.

Explanation of Solution

Molecular compounds are covalent compounds and have van der Waals forces as intermolecular forces. The van der Waals forces are weak intermolecular forces and thus, have a relatively low melting point. In ionic compounds, particles are held together by strong electrostatic forces of attraction and require more energy to overcome these interactions, thus, they have a relatively high melting point.