Liquids and Solids

1. Liquids and Solids Changes of State

2. Objectives • Explain the relationship between equilibrium and changes of state • Define Le Chatelier’s Principle. • Predict changes in equilibrium using Le Chatelier’s Principle. Dry Ice Balloon Explosion (Very Loud Bang) - YouTube

3. Equilibrium Equilibrium – a dynamic state in which two opposing changes occur at equal rates in a closed system. Changes of State solid  liquid melting solid  gas sublimation liquid  solid freezing liquid  gas vaporization gas  liquid condensation gas  solid deposition

5. An Equilibrium Equation • Evaporation of a liquid Liquid + energy  vapor • Condensation of a liquid Vapor  liquid + energy • Liquid-vapor equilibrium liquid + energy vapor

6. Le Chatelier’s Principle A system at equilibrium will shift to offset a stress or change in conditions imposed on the system.

7. Equilibrium and Temperature liquid + energy vapor

8. Equilibrium and Concentration liquid + energy vapor

9. Equilibrium Vapor Pressure • Pressure exerted by a vapor in equilibrium with its corresponding liquid at a given temperature -an increase in temperature causes an increase in equilibrium vapor pressure; result of increased K.E. of the liquid particles.

12. Volatile Liquid – a liquid that readily evaporates at room temp.; liquids with low intermolecular forces. Volatile and Non-volatile liquids

13. Boiling Boiling… …occurs when the equilibrium vapor pressure of a liquid equals the atmospheric pressure …conversion of a liquid to a vapor within the liquid as well as at the surface. Normal Boiling Point: boiling point at standard atmospheric pressure (100oC for water)

14. Boiling

15. Energy and Boiling

16. Molar Heat of Vaporization • The amount of energy needed to vaporize 1 mole of a liquid at its boiling point

17. Freezing and Melting Freezing: Liquid  solid + heat energy Melting: Solid + heat energy  liquid Normal freezing point: temperature at which a solid and liquid are at equilbrium at standard pressure (0oC for water Molar Heat of Fusion – energy required to melt one mole of a solid at its melting point.

19. Phase Diagram Triple Point – temperature and pressure conditions at which the solid, liquid, and gas phases of a substance can coexist at equilibrium Critical temperature - temperature above which a substance cannot exist in the liquid phase. Critical pressure – the lowest pressure at which a substance can exist as a liquid at the critical temperature.

20. Phase Diagram for CO2