At 25°C gallium is a solid with a density of 5.91 g/cm³ and a melting point, 29.8°C, just slightly above room temperature. The density of liquid gallium just above the melting point is 6.1 g/cm³. Based on this information, what unusual feature would you expect to find in the phase diagram of gallium?

Key Concepts

Phase Diagrams

A phase diagram is a graphical representation that shows the phases of a substance at various temperatures and pressures. It typically includes regions where the substance exists as a solid, liquid, or gas, and lines that indicate phase transitions. Understanding phase diagrams is crucial for predicting how a substance behaves under different conditions.

Density Anomalies in Phase Changes

Most substances become denser as they transition from liquid to solid; however, gallium exhibits an unusual behavior where its solid form is less dense than its liquid form. This anomaly can lead to the solid phase floating on the liquid phase, which is contrary to the typical behavior of most materials. Recognizing this property is essential for interpreting gallium's phase diagram.

Melting Point and Phase Transition

The melting point is the temperature at which a solid becomes a liquid, marking a phase transition. For gallium, this occurs at 29.8°C, which is just above room temperature. This low melting point indicates that gallium can exist in both solid and liquid states at relatively mild temperatures, influencing its phase diagram and the behavior of its phases.