1 Intermolecular Attractive Forces: Liquids and Solids Chapter 14 C2 Ch 14 ppt 2 - IMAF's.ppt

In today’s lesson, you will learn: Relationship between vapor pressure and boiling point Effects of atmospheric pressure on boiling point Different types of solid structures 2

3 Properties of Liquids Vapor Pressure Equilibrium In a closed container, liquid particles evaporate while vapor particles condense When the rate of condensation equals the rate of evaporation, the system reaches dynamic equilibrium Before reaching equilibrium: rate of evaporation > rate of condensation After reaching equilibrium: rate of evaporation = rate of condensation

4 Properties of Liquids Vapor Pressure and Boiling Point -Liquids boil when the external pressure equals the vapor pressure (P atm = VP). -Two ways to get a liquid to boil: increase temperature or decrease pressure. -Normal boiling point is the boiling point at 1 atm.

Demonstrations: Effect of lowering atmospheric pressure on boiling point of water: 1.Vacuum pump 2.Sealed jar 5

6 Properties of Liquids Vapor Pressure and Boiling Point The atmosphere is made of many layers. Each layer of air presses down on the layers below, and so the greatest pressure is at sea level where we have the maximum amount of air above. If you had a lot of layers of blankets on your bed, it would feel heavy. This is like the atmosphere at sea level. If you only had 1 blanket, it would feel light. This is like the atmosphere at high altitudes.

7 Properties of Liquids Vapor Pressure and Boiling Point -The boiling temperature of water decreases at higher elevations (lower atmospheric pressure). -For this reason, food will take longer to cook at higher altitudes.

8 Structures of Solids Crystalline Solid -well-ordered, definite arrangements of molecules, atoms or ions. -Crystals have an ordered, repeated structure. -Example: NaCl

9 Structures of Solids Other Kinds of Solid Materials Molecular Solids These are crystalline substances in which the “building blocks” are composed of molecules in place of ions. Example: Table Sugar

10 Molecular Crystals (Ice)

11 Structures of Solids Other Kinds of Solid Materials Network Solids (Covalent Solids) These are crystalline substances in which the “building blocks” are atoms and all the atoms are connected by covalent bonds. Example: Diamond

12 Covalent Crystals Diamond Graphite

13 Structures of Solids Other Kinds of Solid Materials Metals Bonding is strong but nondirectional Electron sea model: valence electrons are mobile, and shared among atoms Example: copper

14 Structures of Solids Other Kinds of Solid Materials Alloys Mixture of elements that has metallic properties Example: brass, bronze, steel, sterling silver

15 Metallic Crystals

16 Crystalline Solids Solid TypeCompositionLattice PointAttractive Force Ionic (NaCl) + & - ionsIonIonic Bond Molecular (ice) 2 or more nonmetals MoleculeIntermolecular Attractive Force Covalent (diamond) Nonmetal atoms Nonmetal Atom Covalent Bond Metallic (copper) Metal atomsMetal CationMetallic Bond