A.P. Chemistry

1. A.P. Chemistry Chapter 11 and Chapter 12 Condensed States Solids and Liquids Solutions

2. Condensed States • liquids and solids.

3. Compare Liquids and Solids to Gases • intermolecular distance • molecular motion • degree of entropy (disorder) • intermolecular attraction Intermolecular bonding • density • compressibility • fluidity

4. Name the phase changes • solid to liquid • solid to gas • liquid to solid • liquid to gas • gas to liquid • gas to solid

5. What phase change is meant by…? • vaporization • liquefaction • boiling • fusion • condensation • melting • freezing • solidifying • deposition • sublimation • evaporation

6. Heating and Cooling Curves • Draw some • Note labels

7. What is the dip for in the cooling curve?

8. Heating and Cooling Curve Examples • In what segments does the kinetic energy change?

9. Heating and Cooling Curves • Steeper slope indicates lower specific heat.

10. Heating and Cooling Curves • What substance has an unusually high specific heat? • Water!

11. Q=mcDT and Q=mL • How much energy is absorbed by liquid dichlorodifluoromethane if it is to absorb the heat from freezing 1000. grams of water put into the freezer at 20.0°C into ice cubes at 0°C? The specific heat of water is 4.18 J/g°C and the heat of fusion for ice is 334 J/g.

12. Example • If the energy goes into evaporating dichlorodifluoromethane, how many kilograms of dichlorodifluoromethane must be involved? The heat of vaporization of dichlorodifluoromethane is 17.4 kJ/mol.

13. Heating and Cooling Curves • In what segments does potential energy of the particles change?

14. Heating and Cooling Curves • Why is the vaporization / condensation plateau is always longer than the freezing / melting plateau?

15. Properties of Liquids • Think of the KMT for liquids and solids: • Consider a liquid in a container • What are its properties / behaviors?

16. Properties of Liquids • Vapor Pressure a measure of the tendency to evaporate. • What factors affect vapor pressure? • Temp, imfs, dissolved solutes

17. Volatile vs. Nonvolatile • a high tendency to evaporate = higher vp = weaker imfs = volatile. • nonvolatile would then be…?

18. Maxwell distributionWhich molecules can evaporate?

19. Vapor pressure data chart • Graph?

21. The Clausius-Clapeyron EQN • relates vapor pressure of a liquid to enthalpy of vaporization. • a graph of vapor pressure of a liquid vs temperature makes a nice curve.

22. The Clausius Clapeyron EQN • Graph of the logarithm of the vapor pressure vs. the reciprocal absolute temp yields line with a negative slope.

23. The Clausius Clapeyron EQN • Putting the values into the point-slope equation for a line yields the Clausius-Clapyron equation. • slope = the opposite of the liquid’s enthalpy of vaporization divided by “R”.

24. The Clausius Clapeyron EQN • P= pressure with consistent units • T = absolute temperature (Kelvin) • R = ideal gas constant: 8.31 J/mol·K • Hvap = enthalpy of vaporization with units J/mol

25. Example • What is the vapor pressure of a liquid at 40°C if it has a normal boiling temp of 120°C and a heat of vaporization of 55 kJ/mol? • 0.0135 atm, 10.3mmHg

26. Example • Calculate the heat of vaporization of diethyl ether C4H10O from the following data: Vapor pressure is 400 mmHg at 18°C and 760 mmHg at 35°C. • 28000 J/mol

27. REVIEW: Condensed States • At what temperature does water boil (or steam condense)? • At what temperature does water freeze (or ice melt)?

28. Boiling Point • Defined: temperature when vp equals atm p. • Why do recipes for high altitudes require longer baking times?

29. Phase Changes • Temps: Melt=freeze boil=condense • The conditions under which a substance exists in its various phases are summarized on its phase diagram. • Examine the phase diagram for water.

30. PHASE Diagrams

35. Phase Diagrams • draw a general phase diagram

36. Phase Diagrams • Identify: • How axes are labeled. • Regions where states of matter exist • The triple point: where all three phases of matter can be in equilibrium

37. Phase Diagrams • critical temperature: above which no condensed state can exist, regardless of the pressure. • critical point: The highest P and T point at which the liquid state can exist.

39. AP Phase diagram questions • Describe the observed change(s) in the substance at 100 K if the pressure changes from 1 to 50 atm.

40. What’s the bpt at 1 atm?

41. Describe the changes at 10 atm when the temperature changes from -100°C to 200°C.

42. Which phase is most dense for the substance, solid or liquid?

43. Liquid Properties • Surface tension: The molecules at the surface of a liquid experience a net force toward the interior of the liquid.

44. Surface Tension • drops can be piled on a penny? • bugs can walk on water. Needles can rest on a water surface. • Liquids bead up into spherical droplets. • Detergents break surface tension; make water feel “wet”.

45. Capillary Rise • Adhesion vs cohesion • attraction a liquid has for its container. • concave vs convex menisci.

46. Capillary Rise • Nonpolar liquids would have less capillary rise in (polar) glass. • narrower capillary, higher rise.

47. Viscosity • resistance to flow. • flow slowly: high viscosity • Viscosity is measurable

48. Viscosity • Society of Automotive Engineers (SAE) rates oils on a numerical viscosity scale • 10W30 • 10W40

49. Solid State • classified as amorphous or crystalline. • Crystalline solids have regular structures with repeating units called unit cells.

50. Types of Solids • Amorphous • “without form” • Imperfect structures