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Vaporization, Viscosity, and IMFs

Vaporization, Viscosity, and IMFs. Molecules in Consider This 1.40. Do all liquids evaporate at the same rate? (Consider This 1.40). Equal volumes of H 2 O, methanol, hexane on sponges Wipe sponges on blackboard Which liquid evaporates fastest? slowest?.

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Vaporization, Viscosity, and IMFs

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  1. Vaporization, Viscosity, and IMFs

  2. Molecules in Consider This 1.40

  3. Do all liquids evaporate at the same rate? (Consider This 1.40) • Equal volumes of H2O, methanol, hexane on sponges • Wipe sponges on blackboard • Which liquid evaporates fastest? slowest?

  4. Relative energies of vaporization? (Consider This 1.41) • Is DEvaporization + (endothermic) or - (exothermic)? • Which liquid has the largest magnitude DEvap? • Sketch an energy diagram to compare the DEvap values of the three liquids.

  5. Energy Level Diagram (Investigate This 1.40) H2O (g) Methanol (g) Energy Hexane (g) H2O, Methanol, Hexane, (l) initially DEvap(H2O) > DEvap(methanol) >DEvap(hexane)

  6. largest smallest DEvap How is DEvap related to IMFs?

  7. computer interfaced temperature probes water ethanol Two liquids about to be heated (Consider This 1.53) • Beakers contain equal masses of water and ethanol at room temp. • Why are the two liquids not the same volume?

  8. Results of heating (1.53) • How are the plots different? The same? • Equal energy was added to both liquids. What accounts for the differences you see?

  9. Results of heating (1.53) • Heat absorbed • disrupts IMFs • and then raises the temperature • Water has stronger IMFs (more extensive H-bonding), so more of the heat is required to disrupt the IMFs. Less heat is available to raise the temperature. • water has a higher specific heat

  10. Viscosity • Resistance to flow • Increases as IMFs get stronger • Decreases as temperature increases

  11. H2COH H bond between two glycerol molecules HCOH H2COH OCH2 H HCOH ….. HOCH2 IMFs in Glycerol?

  12. Viscosity of Glycerol as f(T)

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