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01_Intermolecular Forces (IMF).pptx
- 1. GENERAL CHEMISTRY 2 SubjectTeacher AILENE H. CALAMLAM
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- 4. Intramolecular Forces - forces“within” molecules
- 5. Intermolecular Forces - theattractive forces that exist between molecules
- 6. Intermolecular Forces - theattractive forces that exist between molecules - Intermolecular forces are weak compared to intramolecular forces
- 7. 7 Intermolecular Forces In orderof increasing strength, these are: •London dispersion forces •dipole–dipole interactions •hydrogen bonding
- 8. 8 Intermolecular Forces The strengthof the intermolecular forces determines whether a compound has a high or low melting point and boiling point, and thus whether it is a solid, liquid, or gas at a given temperature.
- 9. 9 London Dispersion Forces Londondispersion forces are very weak interactions due to the momentary changes in electron density in a molecule.
- 10. 10 More e− density inone region creates a partial negative charge (δ−). Less e− density in one region creates a partial positive charge (δ+). London Dispersion Forces
- 11. 11 London Dispersion Forces •The change in electron density creates a temporary dipole.
- 12. 12 London Dispersion Forces •The change in electron density creates a temporary dipole. • The weak interaction between these temporary dipoles constitutes London dispersion forces.
- 13. 13 London Dispersion Forces •The change in electron density creates a temporary dipole. • All covalent compounds exhibit London dispersion forces. • The weak interaction between these temporary dipoles constitutes London dispersion forces.
- 14. 14 London Dispersion Forces •The change in electron density creates a temporary dipole. • All covalent compounds exhibit London dispersion forces. • The weak interaction between these temporary dipoles constitutes London dispersion forces. • The larger the molecule, the larger the attractive force, and the stronger the intermolecular forces.
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- 16. 16 Dipole–Dipole Interactions Dipole–dipole interactionsare the attractive forces between the permanent dipoles of two polar molecules.
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- 19. 19 Draw the individualdipoles of two H-Cl molecules and show how the dipoles are aligned in a dipole–dipole interaction.
- 20. 20 Hydrogen Bonding Hydrogen bondingoccurs when a hydrogen atom bonded to O, N, or F is electrostatically attracted to an O, N, or F atom in another molecule.
- 21. 21 Hydrogen Bonding Hydrogen bondsare the strongest of the three types of IMF.
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- 28. 28 Concept Check Which arestronger, intramolecular bonds or intermolecular forces?
- 29. 29 Concept Check Which arestronger, intramolecular bonds or intermolecular forces?
- 30. 30 Which has thestronger intermolecular forces? N2 H2O Explain. Concept Check
- 31. 31 Which has thestronger intermolecular forces? N2 H2O Explain. Concept Check
- 32. 32 Draw two Lewisstructures for the formula C2H6O and compare the boiling points of the two molecules. Concept Check
- 33. Identify the typeof IMF present the ff. molecules: 1. CH3Cl 2. NH3 3. HCl 4. CCl4 5. HF 33
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- 35. 10. Which moleculesare capable of intermolecular hydrogen bonding? 35
- 36. 36 Boiling Point andMelting Point • The boiling point is the temperature at which a liquid is converted to the gas phase. • The melting point is the temperature at which a solid is converted to the liquid phase.
- 37. 37 Boiling Point andMelting Point • The stronger the intermolecular forces, the higher the boiling point and melting point.
- 38. 38 Intermolecular Forces Boiling Pointand Melting Point
- 39. 39 Intermolecular Forces Boiling Pointand Melting Point • Both propane and butane have London dispersion forces and nonpolar bonds.
- 40. 40 Intermolecular Forces Boiling Pointand Melting Point • In this case, the larger molecule will have stronger attractive forces.
- 41. 41 Which compound ineach pair has the higher boiling point?
- 42. 42 Which compound ineach pair has the higher melting point?
- 43. Explain why CO2is a gas at room temperature but H2O is a liquid. 43
- 44. 44 Vapor Pressure • Evaporationis the conversion of liquids into the gas phase. •Evaporation is endothermic—it absorbs heat from the surroundings.
- 45. 45 Vapor Pressure • Condensationis the conversion of gases into the liquid phase. • Condensation is exothermic— it gives off heat to the surroundings.
- 46. 46 Vapor Pressure Vapor pressure isthe pressure exerted by gas molecules in equilibrium with the liquid phase.
- 47. 47 Vapor Pressure Vapor pressure increaseswith increasing temperature.
- 48. 48 •The stronger theintermolecular forces, the lower the vapor pressure at a given temperature. Vapor Pressure
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- 51. Which molecule ineach pair has the higher vapor pressure at a given temperature? a. CH4 or NH3 b. CH4 or C2H6 c. C2H6 or CH3OH 51
- 52. 52 Viscosity Viscosity is ameasure of a fluid’s resistance to flow freely. •A viscous liquid feels “thick.”
- 53. 53 Viscosity • Compounds withstrong intermolecular forces tend to be more viscous than compounds with weaker forces.
- 54. 54 Viscosity • Substances composedof large molecules tend to be more viscous, too, because large molecules do not slide past each other as freely.
- 55. Explain why benzeneis less viscous than water, but ethylene glycol is more viscous than water. 55
- 56. 56 Surface Tension Surface tensionis a measure of the resistance of a liquid to spread out. Interior Surface
- 57. 57 Surface Tension Interior moleculesin a liquid are surrounded by IMF on all sides.
- 58. 58 Surface Tension Surface molecules onlyexperience IMF from the sides and from below.
- 59. 59 Surface Tension •The strongerthe intermolecular forces, the stronger the surface molecules are pulled down toward the interior of a liquid and the higher the surface tension.
- 60. 60 Surface Tension •The strongerthe intermolecular forces, the stronger the surface molecules are pulled down toward the interior of a liquid and the higher the surface tension. •Water has a very high surface tension because of its strong intermolecular hydrogen bonding.
- 61. 61 ENRICHMENT (10 MINS) Todetermine the polarity of a molecule, both the bonds present and the overall shape of the molecule should be considered. Two or more polar bonds may cancel each other out leading to a nonpolar molecule.
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