by Steven S. Zumdahl & Donald J. DeCoste University of Illinois Introductory Chemistry: A Foundation, 6 th Ed. Introductory Chemistry, 6 th Ed. Basic Chemistry, 6 th Ed.

Chapter 14 Liquids and Solids

Copyright © Houghton Mifflin Company. All rights reserved. 14 | 3 Water Colorless, odorless, and tasteless Density of ice < than density of liquid water –Water expands when it freezes –Ice floats on water –Density of liquid water = 1.00 g/mL –Density of ice = g/mL

Copyright © Houghton Mifflin Company. All rights reserved. 14 | 4 Water (cont.) Freezes at 0°C Boils at 100°C at 1.00 atm pressure –Boiling point increases as atmospheric pressure increases Temperature stays constant during a state change Relatively large amounts of energy needed to melt solid or boil liquid

Copyright © Houghton Mifflin Company. All rights reserved. 14 | 5 Water (cont.)

Copyright © Houghton Mifflin Company. All rights reserved. 14 | 6 Structures of the States of Matter

Copyright © Houghton Mifflin Company. All rights reserved. 14 | 7 Energy Requirements for State Changes In order to change a liquid to a gas, it is necessary to supply the energy required to overcome the intermolecular attractions. –Not break bonds (intramolecular forces) Heat of vaporization: the energy required to boil 1 mole of a liquid  H vaporization = 40.6 kJ/mol for water at 100°C

Copyright © Houghton Mifflin Company. All rights reserved. 14 | 8 Energy Requirements for State Changes (cont.) In order to change a solid to a liquid it is necessary to supply the energy required to overcome the intermolecular attractions. Heat of Fusion: the energy required to melt 1 mole of a solid  H fusion = 6.02 kJ/mol for ice at 0°C

Copyright © Houghton Mifflin Company. All rights reserved. 14 | 9 Why do Molecules Attract Each Other? Intermolecular attractions are due to attractive forces between opposite charges. + ion to - ion + end of polar molecule to - end of polar molecule Larger the charge, stronger the attraction Even non-polar molecules have attractions due to opposite charges

Copyright © Houghton Mifflin Company. All rights reserved. 14 | 10 Intermolecular Attraction Much weaker than ionic or covalent bonds There are several types: London dispersion forces, dipole-dipole attraction, and hydrogen bonding

Copyright © Houghton Mifflin Company. All rights reserved. 14 | 11 Intermolecular Attraction (cont.) London dispersion forces: intermolecular attractions between non-polar molecules; the weakest Dipole-dipole: intermolecular attraction due to molecular polarity Hydrogen bond: a special type of very strong dipole-dipole intermolecular attraction –Water has very strong H-bonds

Copyright © Houghton Mifflin Company. All rights reserved. 14 | 12 London Dispersion Forces Also known as induced dipoles Caused by electrons on one molecule distorting the electron cloud on another All molecules have them Temporary

Copyright © Houghton Mifflin Company. All rights reserved. 14 | 13 London Dispersion Forces (cont.) Size of the London dispersion force depends on the number of electrons and shapes of molecules –The larger the molar mass, the larger the induced dipole

Copyright © Houghton Mifflin Company. All rights reserved. 14 | 14 London Dispersion Forces (cont.)

Copyright © Houghton Mifflin Company. All rights reserved. 14 | 15 Dipole-Dipole Attraction Individually, dipole-dipole attraction is stronger than London dispersion forces.

Copyright © Houghton Mifflin Company. All rights reserved. 14 | 16 Dipole-Dipole Attraction (cont.)

Copyright © Houghton Mifflin Company. All rights reserved. 14 | 17 Hydrogen Bonding Molecules that have H- bonded to F, O, or N have unusually strong intermolecular forces called hydrogen bonding.

Copyright © Houghton Mifflin Company. All rights reserved. 14 | 18 Hydrogen Bonding (cont.)

Copyright © Houghton Mifflin Company. All rights reserved. 14 | 19 Attractive Forces and Properties Larger attractive forces between molecules in pure substance means: –Higher boiling point –Higher melting point (though also depends on crystal packing )

Copyright © Houghton Mifflin Company. All rights reserved. 14 | 20 Attractive Forces and Properties (cont.) Like dissolves like –Polar molecules dissolve in polar solvents water, alcohol molecules with O or N more soluble in H 2 O due to H-bonding with H 2 O –Non-polar molecules dissolve in non-polar solvents oils and gasoline

Copyright © Houghton Mifflin Company. All rights reserved. 14 | 21 Evaporation Also known as vaporization Requires overcoming intermolecular attractions Heat of vaporization is amount of energy needed to evaporate 1 mole of liquid Reverse is condensation

Copyright © Houghton Mifflin Company. All rights reserved. 14 | 22 Evaporation (cont.)

Copyright © Houghton Mifflin Company. All rights reserved. 14 | 23 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 | 24 Vapor Pressure (cont.) Liquid boils when its vapor pressure = atmospheric pressure –Normal boiling point –Raising external pressure raises boiling point, & vice-versa

Copyright © Houghton Mifflin Company. All rights reserved. 14 | 25 Vapor Pressure (cont.) Liquid just poured into open container, little vapor Evaporation faster than condensation Evaporation as fast as condensation Equilibrium

Copyright © Houghton Mifflin Company. All rights reserved. 14 | 26 Solids Amorphous solids –Show no definite structure glass, plastic, rubber –Tend to soften and melt over a temperature range Crystalline solids –Orderly, repeating 3-dimensional pattern –Pattern = crystal lattice –Melt at one specific temperature

Copyright © Houghton Mifflin Company. All rights reserved. 14 | 27 Types of Crystalline Solids

Copyright © Houghton Mifflin Company. All rights reserved. 14 | 28 Types of Crystalline Solids (cont.)

Copyright © Houghton Mifflin Company. All rights reserved. 14 | 29 Types of Crystalline Solids (cont.)

Copyright © Houghton Mifflin Company. All rights reserved. 14 | 30 Types of Crystalline Solids (cont.)

Copyright © Houghton Mifflin Company. All rights reserved. 14 | 31 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 non- directional e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e

Copyright © Houghton Mifflin Company. All rights reserved. 14 | 32 Metallic Bonding & Properties Electrical conductors because of mobile electrons –Electrical current is moving electrons Thermal conductors because of mobile electrons –Small, light, mobile electrons can transfer kinetic energy quicker than larger particles Malleable & ductile because metal ions can slide past each other in crystal –Attractive forces are adjustable because electrons are mobile

Copyright © Houghton Mifflin Company. All rights reserved. 14 | 33 Metallic Bonding & Properties (cont.) Luster due to the mobile electrons on the surface absorbing the outside light and then emitting it at the same frequency Melting points are relatively high due to strong attractions between metal ions and electrons –Stronger ion charge = larger attraction –Smaller ion size = larger attraction

Copyright © Houghton Mifflin Company. All rights reserved. 14 | 34 Alloys Alloys: mixtures of elements that show metallic properties Substitutional alloys have some host metal atoms replaced by metal atoms of similar size. Interstitial alloys have small atoms occupying some of the holes in the crystal lattice of the host metal.

Copyright © Houghton Mifflin Company. All rights reserved. 14 | 35 Alloys