Physical Transformations and Phase Diagrams Quiz

Terms and Definitions

• A homogeneous substance is a form of matter that is uniform in chemical composition and physical state.
• The Gibbs energy is minimized and in equilibrium at the temperature where two phases co-exist, known as the phase equilibrium temperature.

Phase Diagrams

• A phase diagram visually represents the different phases of a substance under varying temperature and pressure conditions.
• Metastable phases are states that are stable under certain conditions, but not in the lowest energy state possible.
• Phase boundaries on a phase diagram indicate the conditions (temperature and pressure) at which two phases coexist.

Additional Concepts

• A phase diagram maps the stability of phases under different temperature and pressure conditions.
• Supercritical fluid occurs at the critical temperature, where the distinction between liquid and gas phases disappears.
• The critical pressure is the pressure exerted at the critical temperature.

Boiling Points and Pressure Conditions

• At a lower pressure than the normal boiling point, the standard boiling point for a liquid is slightly lower.
• The positive slope of the solid-liquid boundary in carbon dioxide signifies that solid CO2 (dry ice) converts to liquid under increased pressure.

Triple Points and Sublimation

• At the triple point condition, solid, liquid, and vapor phases coexist in equilibrium.
• The liquid phase of carbon dioxide sublimates at any temperature under a pressure lower than its triple point pressure.

Vapor Pressure and Temperature Relations

• The temperature at which vapor pressure equals external pressure is known as the boiling point.
• Unique phase behavior occurs at no other combination of pressure and temperature, indicating specific stability conditions.

Pressure Conditions for CO2

• To obtain liquid carbon dioxide at any temperature, a pressure greater than the triple point pressure is necessary.