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A.P. Chemistry

A.P. Chemistry. Chapter 11 and Chapter 12 Condensed States Solids and Liquids Solutions. Condensed States. liquids and solids. Compare Liquids and Solids to Gases. intermolecular distance molecular motion degree of entropy (disorder) intermolecular attraction Intermolecular bonding

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A.P. Chemistry

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  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?

  20. 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.

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

  22. 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”.

  23. 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

  24. 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

  25. 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

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

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

  28. 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.

  29. PHASE Diagrams

  30. Phase Diagrams • draw a general phase diagram

  31. 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

  32. 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.

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

  34. What’s the bpt at 1 atm?

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

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

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

  38. 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”.

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

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

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

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

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

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

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