Chapter 14 Liquids and Solids Review Intermolecular attractions

Intermolecular attractions • The attractions between different molecules • Covalent bonds are intramolecular Copyright

Intermolecular attractions (cont. ) • Hydrogen bond: a special type of very strong dipole-dipole

Hydrogen bonding • -O-H • -N-H • F-H Copyright © Houghton Mifflin Company. All

Other dipole-dipole attraction • permanent dipoles Copyright © Houghton Mifflin Company. All rights reserved.

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How to Decide if its Equal or Not? Electronegativity • A number that tells

Which bonds are polar? • Polarity of a bond depends on the difference between

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London Dispersion Forces • All molecules have them • Weakest intermolecular force • But,

Questions about which boiling point is highest? • What intermolecular forces exist in each

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QUESTION • Which of the compounds below has the highest boiling point? A. B.

The Saturated Hydrocarbons, or Alkanes CH 4 C 2 H 6 C 3 H

QUESTION • Which of the following is more likely to be a liquid at

Water • Freezes at 0°C • Boils at 100°C at 1. 00 atm pressure

Water (cont. ) Copyright © Houghton Mifflin Company. All rights reserved. 14 | 19

Vapor Pressure • Pressure exerted by a vapor in equilibrium with a liquid –

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Relationship • As the strength of intermolecular forces increases, vapor pressure decreases. Copyright ©

Heat of vaporization • The energy required to boil 1 mole of a liquid

Heat of fusion • The energy required to melt 1 mole of a solid

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Types of Crystalline Solids Copyright © Houghton Mifflin Company. All rights reserved. 14 |

Types of Crystalline Solids (cont. ) atomic (includes metals, too) ionic Copyright © Houghton

Melting Point • Depends on the strength of intermolecular attractions. Copyright © Houghton Mifflin

Melting Point • Depends on the strength of intermolecular attractions. • Diamond has covalent

Melting Point • • • Depends on the strength of intermolecular attractions. Diamond has

Ions dissolved in water conduct electricity Copyright © Houghton Mifflin Company. All rights reserved.

Types of Crystalline Solids (cont. ) • Atomic solids that are made of metal

Properties of metals and alloys • Electrical conductors • Thermal conductors • Malleable &

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Chapter 14 Liquids and Solids Review

Intermolecular attractions (cont. ) • Hydrogen bond: a special type of very strong dipole-dipole intermolecular attraction – Water has very strong H-bonds • Dipole-dipole: other intermolecular attraction due to molecular polarity • London dispersion forces: intermolecular attractions between non-polar molecules; the weakest Copyright © Houghton Mifflin Company. All rights reserved. 14 | 3

How to Decide if its Equal or Not? Electronegativity • A number that tells us the ability of an atom (engaged in a bond) to attract electrons to itself. • Polarity of a bond depends on the difference between the electronegativities of two atoms. ✓(nonpolar) ≤ 0. 4 < polar < 2. 0 ≤ (ionic) • Any molecule that has a positive end a negative end is said to be ✓Polar ✓aka: a dipole ✓aka: has a dipole moment. Copyright © Houghton Mifflin Company. All rights reserved. 14 | 8 8

Which bonds are polar? • Polarity of a bond depends on the difference between the electronegativities of two atoms • (nonpolar) ≤ 0. 4 < polar < 2. 0 ≤ (ionic) • Any molecule that has a positive end a negative end is said to be ✓Polar ✓aka: a dipole ✓aka: has a dipole moment. Copyright © Houghton Mifflin Company. All rights reserved. 14 | 9

London Dispersion Forces • All molecules have them • Weakest intermolecular force • But, if the molecules don’t have hydrogen bonding or any dipole-dipole attractions, the still have London dispersion forces. Copyright © Houghton Mifflin Company. All rights reserved. 14 | 12

Questions about which boiling point is highest? • What intermolecular forces exist in each case? • If polar, how polar? • If only London dispersion forces exist, then look at the molecular weight. Copyright © Houghton Mifflin Company. All rights reserved. 14 | 13

The Saturated Hydrocarbons, or Alkanes CH 4 C 2 H 6 C 3 H 8 C 4 H 10 C 5 H 12 C 6 H 14 C 7 H 16 C 8 H 18 C 9 H 20 C 10 H 22 Melting Point (o. C) -183 -190 -138 -130 -95 -91 -57 -51 -30 Boiling Point (o. C) -164 -89 -42 -0. 5 36 69 98 125 151 174 undecane C 11 H 24 -25 196 liquid dodecane C 12 H 26 -10 216 liquid eicosane C 20 H 42 37 343 solid 66 450 solid 14 | 16 Name methane propane butane pentane hexane heptane octane nonane decane Molecular Formula triacontane C 30 H 62 Copyright © Houghton Mifflin Company. All rights reserved. State at 25 o. C gas gas liquid liquid

Vapor Pressure • Pressure exerted by a vapor in equilibrium with a liquid – Or solid • Increases with temperature • Larger intermolecular forces = lower vapor pressure Copyright © Houghton Mifflin Company. All rights reserved. 14 | 20

Heat of vaporization • The energy required to boil 1 mole of a liquid – Hvaporization = 40. 6 k. J/mol for water at 100°C • How much energy is required to turn 0. 5 mole of water into gas? Copyright © Houghton Mifflin Company. All rights reserved. 14 | 23

Heat of vaporization • The energy required to boil 1 mole of a liquid – Hvaporization = 40. 6 k. J/mol for water at 100°C • How much energy is required to turn 0. 5 mole of water into gas? • Answer: 20. 3 k. J Copyright © Houghton Mifflin Company. All rights reserved. 14 | 24

Heat of fusion • The energy required to melt 1 mole of a solid – Hvaporization = 6. 02 k. J/mol for ice at 0°C • How much energy is required to turn 36 g of ice into liquid? Copyright © Houghton Mifflin Company. All rights reserved. 14 | 25

Heat of fusion • The energy required to melt 1 mole of a solid – Hvaporization = 6. 02 k. J/mol for ice at 0°C • How much energy is required to turn 36 g of ice into liquid? • Answer: 12. 04 k. J Copyright © Houghton Mifflin Company. All rights reserved. 14 | 26

Melting Point • Depends on the strength of intermolecular attractions. • Diamond has covalent bonds. 4200 K • Sodium chloride has ionic bonds. Copyright © Houghton Mifflin Company. All rights reserved. 14 | 33

Melting Point • Depends on the strength of intermolecular attractions. • Diamond has covalent bonds. 4200 K • Sodium chloride has ionic bonds. 1074 K Copyright © Houghton Mifflin Company. All rights reserved. 14 | 34

Melting Point • Depends on the strength of intermolecular attractions. • Diamond has covalent bonds. 4200 K • Sodium chloride has ionic bonds. 1074 K • Water has hydrogen bonds. Copyright © Houghton Mifflin Company. All rights reserved. 14 | 35

Melting Point • Depends on the strength of intermolecular attractions. • Diamond has covalent bonds. 4200 K • Sodium chloride has ionic bonds. 1074 K • Water has hydrogen bonds. 273 K Copyright © Houghton Mifflin Company. All rights reserved. 14 | 36

Melting Point • • • Depends on the strength of intermolecular attractions. Diamond has covalent bonds. 4200 K Sodium chloride has ionic bonds. 1074 K Water has hydrogen bonds. 273 K Hexane (C 6 H 14) has London dispersion forces. Copyright © Houghton Mifflin Company. All rights reserved. 14 | 37

Melting Point • • • Depends on the strength of intermolecular attractions. Diamond has covalent bonds. 4200 K Sodium chloride has ionic bonds. 1074 K Water has hydrogen bonds. 273 K Hexane (C 6 H 14) has London dispersion forces. 178 K Copyright © Houghton Mifflin Company. All rights reserved. 14 | 38

Melting Point • • • Depends on the strength of intermolecular attractions. Diamond has covalent bonds. 4200 K Sodium chloride has ionic bonds. 1074 K Water has hydrogen bonds. 273 K Hexane (C 6 H 14) has London dispersion forces. 178 K Helium has London dispersion forces. Copyright © Houghton Mifflin Company. All rights reserved. 14 | 39

Melting Point • • • Depends on the strength of intermolecular attractions. Diamond has covalent bonds. 4200 K Sodium chloride has ionic bonds. 1074 K Water has hydrogen bonds. 273 K Hexane (C 6 H 14) has London dispersion forces. 178 K Helium has London dispersion forces. ~1 K Copyright © Houghton Mifflin Company. All rights reserved. 14 | 40

Types of Crystalline Solids (cont. ) • Atomic solids that are made of metal atoms – Metal atoms release their valence electrons – Metal cations fixed in a “sea” of mobile electrons = electron sea model – Leads to strong attractions that are nondirectional + + + ee- + + + ee- Copyright © Houghton Mifflin Company. All rights reserved. + + + ee- + + 14 | 42