Question

As a metal such as lead melts, what happens to (a) the average kinetic energy of the atoms and (b) the average distance between the atoms?

Short answer

During the melting process of a metal like lead, (a) the average kinetic energy of the atoms increases as the absorbed heat raises the metal's temperature, and (b) the average distance between atoms increases as the metal transitions from a close-packed solid lattice to a more disordered liquid state.

Step-by-step solution

Understand the melting process

When a metal goes from a solid to a liquid state, it undergoes a phase change called melting. During this process, the metal absorbs heat which results in increased kinetic energy and potential energy of the atoms.

Analyze the average kinetic energy during melting

The average kinetic energy of the atoms is dependent on the temperature of the metal. When heat is absorbed during the melting process, the temperature of the metal increases, and so does the average kinetic energy of its atoms. So, during melting, the average kinetic energy of the atoms increases.

Analyze the average distance between atoms during melting

In the solid phase, metal atoms are arranged in a close-packed structure with relatively small distances between the atoms. When the metal melts, the structure changes from a solid lattice to a disordered liquid, where the atoms have a higher degree of freedom. This leads to an increase in the average distance between the atoms as they are no longer confined to the regular structure of the solid lattice.

Summarize the findings

During the melting process of a metal such as lead, (a) the average kinetic energy of the atoms increases due to the absorbed heat, which raises the temperature of the metal, and (b) the average distance between the atoms increases as the metal undergoes a phase change from a close-packed solid lattice to a more disordered liquid state.