What does a phase diagram show?

What does a phase diagram show?

• A. A graph of reaction rates between phases.
• B. A plot of solubility with temperature for solids.
• C. A diagram showing the stability of phases at different temperatures and pressures.
• D. A chart of densities of phases.

Answer: (C)

A phase diagram shows which form a substance tends to be in under different temperatures and pressures. The axes are typically temperature and pressure, and the diagram maps regions where the solid, liquid, or gas is the most stable phase. The boundaries between these regions are lines of equilibrium, where two phases can coexist (such as solid and liquid in a melting line, or liquid and gas in a boiling line). Points like the triple point and, for many substances, the critical point help describe special conditions where unusual behavior occurs. This makes phase diagrams fundamentally about stability across temperature and pressure, not about how fast reactions occur, how much something dissolves with temperature, or the densities of the phases.

A phase diagram shows which form a substance tends to be in under different temperatures and pressures. The axes are typically temperature and pressure, and the diagram maps regions where the solid, liquid, or gas is the most stable phase. The boundaries between these regions are lines of equilibrium, where two phases can coexist (such as solid and liquid in a melting line, or liquid and gas in a boiling line). Points like the triple point and, for many substances, the critical point help describe special conditions where unusual behavior occurs. This makes phase diagrams fundamentally about stability across temperature and pressure, not about how fast reactions occur, how much something dissolves with temperature, or the densities of the phases.