10,000 1,000 Solid Supercritical Fluid Pressure, atm 100 Liquid Critical point Triple point 10 1 0.1 -100 -80 -60 -40 -20 0 20 40 60 Temperature, °C Vapour
The Correct Answer and Explanation is:
Correct Answer: Phase Diagram Interpretation
The diagram provided is a phase diagram of a substance showing the states of matter (solid, liquid, vapor, and supercritical fluid) at different temperatures and pressures. The key features include:
- Triple Point: The point where solid, liquid, and vapor phases coexist in equilibrium.
- Critical Point: The end point of the liquid-vapor boundary where a supercritical fluid forms.
- Supercritical Fluid Region: The area beyond the critical point.
- Phase Boundaries: Curves separating solid, liquid, and vapor regions.
Explanation (300 words)
The graph represents a phase diagram that outlines how a substance behaves under various temperature and pressure conditions. It includes four primary regions—solid, liquid, vapor, and supercritical fluid. The y-axis shows pressure in atmospheres, while the x-axis shows temperature in degrees Celsius.
Starting from low temperatures and pressures, the substance exists as a solid. As temperature or pressure increases, the phase can shift. For instance, increasing the temperature at constant low pressure causes the substance to sublimate directly into vapor, bypassing the liquid state. This transition occurs along the solid-vapor boundary.
At a specific combination of temperature and pressure known as the triple point, all three phases—solid, liquid, and vapor—coexist in equilibrium. Beyond this point, raising temperature at moderate pressure allows the substance to melt into liquid and then boil into vapor, following the typical path of phase changes.
As temperature and pressure continue to rise, the diagram shows a critical point where the boundary between liquid and vapor ends. Beyond this critical point, the substance becomes a supercritical fluid—a phase that exhibits properties of both gases and liquids. Supercritical fluids can diffuse through solids like a gas and dissolve materials like a liquid.
This phase diagram is essential in chemistry and engineering because it helps predict the state of a substance under specific conditions. It is particularly useful in fields like materials science, geology, and thermodynamics. By examining phase boundaries and critical conditions, one can determine the appropriate state and transitions for practical and experimental applications.
