1. States of Matter and Intermolecular Forces

2. 3 Phases of Matter  Solid  Liquid  Gas

3. How do particles move in a solid?

4. Solids  Have a definite shape/structure  Very little particle movement—fixed position

6. Liquids  Limited structure to particles  Movement is less restricted, particles can move around and collide with each other  Conform to a container’s shape

8. Gases  No structure  Movement is not restricted  Particles are always in motion  Expansion occurs

10. Phase Changes  Physical change of a chemical compound  Change of state  Types:  Melting  Freezing  Vaporization  Condensation  Sublimation  Deposition

11. Evaporation/Vaporization  Liquid---gas, endothermic  Liquid molecules gain enough energy to enter the gaseous state via breaking intermolecular forces.  Enthalpy of vaporization—  Amount of heat necessary to evaporate a liquid at constant temperature  kJ/mole  Table 11.1 (p. 435)

12. Condensation  Gas-----liquid  Exothermic process

13. Example 1 At 25°C, how much heat is required to evaporate 175 g of methanol?

14. Example 2: Which liquid in Table 11.1 (p. 435) requires the lowest amount of heat for vaporization?

15. Vaporization/Condensation  Processes exist at the same time  Dynamic equilibrium is established  Rate of vaporization = rate of condensation  No net change in molecular movement  Many factors determine how long it will take for equilibrium to be established

17. Vapor Pressure  Characteristic of liquid  Partial pressure of vapor when it exists with a liquid in dynamic equilibrium under constant temperature  Dependent on liquid type and temperature at equilibrium  INCREASE vapor pressure of liquid, INCREASE temperature

18. Vapor Pressure Curve  Figure 11.4 p. 439

19. Volatile vs. Nonvolatile Liquids 1) Volatile Liquids  WEAK intermolecular forces  High vapor pressure  Ex. Gasoline, alcohols, “Whoosh Bottle” 2) Nonvolatile Liquids  STRONG intermolecular forces  Low vapor pressure

20. Whoosh Bottle Demo Video  http://www.youtube.com/watch?v=-BtFHg-lm_M http://www.youtube.com/watch?v=-BtFHg-lm_M

21. Boiling Point  Liquid characteristic  Vaporization present throughout the liquid  Point where vapor pressure = atmospheric pressure  Aids in liquid identification  Decrease atmospheric pressure with increased altitude, lowers boiling point

23. Boiling Point (cont.)  Critical temperature/pressure (T C, P C )  Highest temperature with liquid and vapor present as physically different states in equilibrium  Point where increased pressure only will result in condensation  Critical Point  Actual physical condition where critical temperature and pressure achieved

24. Melting/Melting Point  Melting/freezing point  Temperature when solid “melts”  Temperature when liquid becomes solid  For water = _________  Enthalpy (heat) of fusion– Δh fusion  Amount of heat needed to convert a certain amount of a solid to a liquid  Melting—endothermic  Freezing—exothermic (- value)

25. Cooling/Heating Curves  Figure 11.7 p. 444

26. Cooling/Heating Curves

27. Sublimation  Solid  Gas  Some solid compounds are volatile enough to have a vapor pressure and convert to gas  Ex. Mothballs, dry ice  Rate of sublimation = rate of deposition  Sublimation curve  Sublimation pressure—  Pressure of a vapor existing in equilibrium with a solid

28. Enthalpy (heat) of sublimation  = ΔH fusion + ΔH vapn