1. Changes Of state Chapter 12.3 Objectives: Explain the relationship between equilibrium and changes of state. Predict changes in equilibrium using Le Chatelier’s principle. Explain what is meant by equilibrium vapor pressure. Describe the processes of boiling, freezing, melting, and sublimation. Interpret phase diagrams.
2. Equilibrium Defined as: a dynamic condition in which two opposing changes occur at equal rates in a closed system. Closed system: matter cannot enter or leave, but energy can Analogy: Public swimming pool Morning: more people entering than leaving Afternoon: number of people entering and leaving are the same This would be equilibrium
3. Equilibrium and Changes of State Evaporation of water in a closed container Vacuum over liquid Same temperature as surroundings ( 25oC) Water and container are the system **Single Phase Liquid **Evaporation begins at constant rate **Rate of evaporation is equal to rate of condensation **Some condensation occurs Equilibrium
4. Possible Phase Changes Change of State Process Example Solid Liquid melting candle Solid Gas sublimation Rock show Liquid Solid freezing Lake freezing Liquid Gas vaporization puddle Gas Liquid condensation bathroom Gas Solid deposition Frost
5. An Equilibrium Equation liquid + heat energy vapor vapor liquid + heat energy liquid + heat energy vapor Reversible: vapor is being formed at the same RATE as liquid.
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7. Shifts in Equilibrium liquid + heat energy vapor Change Shift _ Add liquid Right Remove liquid Left Add Vapor Left Remove Vapor Right Decrease Container Volume Left Increase Container Volume Right Decrease in Temperature Left Increase in Temperature Right
8. Equilibrium Vapor Pressure of a Liquid Defined as: the pressure exerted by a vapor in equilibrium with its corresponding liquid at a given temperature
9. Volatile and Nonvolatile Liquids Volatile Liquids: Liquids that evaporate readily Weak attractive forces Nonvolatile Does not evaporate readily Stronger attractive forces Equilibrium vapor pressure Depends on Nature of liquid Temperature
10. Boiling Conversion of a liquid to a vapor within the liquid to a vapor within the liquid as well as at its surface. Occurs when Equilibrium vapor pressure = atmospheric pressure Boiling Point Temperature at which the equilibrium vapor pressure of the liquid equals the atmospheric pressure High elevations Lower atmospheric pressure Water boils at lower temperatures Food takes longer to cook
11. Molar Heat of Vaporization The amount of heat energy needed to vaporize one mole of liquid at its boiling point. 100.0 Temperature(oC) 0.0 Heat of vaporization Heat added (KJ)
12. Freezing and Melting Freezing point Temperature at which the solid and liquid are in equilibrium at 1 atm pressure. Melting is the reverse of freezing. liquid solid + heat energy solid + heat energy liquid solid + heat energy liquid
13. Molar Heat of Fusion The amount of heat energy required to melt one mole of solid at its melting point. 100.0 Temperature(oC) 0.0 Heat added (KJ) Heat of fusion
14. Sublimation and Deposition Sublimation Change of state from a solid directly to a gas Deposition Change of state from a gas directly to a solid solid + heat energy vapor
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16. indicates the temperature and pressure conditions at which the solid, liquid, and vapor of a substance can coexist at equilibrium.
