Chapter 14.1, Problem 3R

To determine

The behavior of the particles of the substance at its melting point.

Explanation of Solution

Introduction:

The kinetic energy of the particles of the substance varies with the temperature of the substance. The kinetic energy of the particles increases with an increase in the temperature of the substance.

The particles of the substance in the solid-state remain fixed and do not move within the substance because the molecular attraction force between the particles is very strong. The strong attraction force between the particles prevents the movement of the particles in the substance.

The rise in temperature of the substance is necessary to melt the substance, and this increase in the temperature of a substance reduces the attraction force between the particles. The movement of the particles starts with the melting of the substance. The particle becomes free to move at the melting point of the substance. The free movement of the particles becomes possible due to a reduction in the attraction force between the particles.

Conclusion:

Thus, the particles of the substance move freely at the melting point of the substance.