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Great Ideas in Science: Lecture 6 – Properties of Materials. Professor Robert Hazen PROV 301. KEY IDEA: Properties of materials depend on their atoms, and how those atoms are linked together. Tonight ’ s Outline. Review Chemical Bonding Chemical Reactions Properties of Materials
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Great Ideas in Science:Lecture 6 – Properties of Materials Professor Robert Hazen PROV 301 KEY IDEA: Properties of materials depend on their atoms, and how those atoms are linked together
Tonight’s Outline • Review Chemical Bonding • Chemical Reactions • Properties of Materials • States of matter • Changes of state • Strength of materials • Electrical properties
Chemical Bonding Key Idea: Atoms link together by the rearrangement of their electrons 1. “Magic” numbers of electrons (i.e. 2, 10, 18, and 36) form very stable atoms. 2. Electrons may be transferred or shared to form stable bonds. 3. Ionic, metallic, and covalent bonds
Ionic Bonding Ionic Bonding Na Cl
Ionic Bonding Mg + 2Cl MgCl2 Mg + 2Cl
Ionic Bonding Fluorite CaF2
Ionic Bonding Two properties of materials with ionic bonds: 1. Insulates electricity—“insulator” (electrons don’t move) 2. Tough but brittle—cup demo.
Metallic Bonding Three properties of materials With metallic bonds: 1. Conducts electricity—Wire (electrons free to move) 2. Malleable—Coat hanger 3. Shiny
Covalent Bonding Hydrogen
Covalent Bonding WATER
1 C 4 2 3 (R)-enantiomer Covalent Bonding: Carbon CARBON BONDING Organic Chemistry
1 C 4 2 3 (R)-enantiomer Covalent Bonding: Carbon CARBON BONDING Organic Chemistry
SOLIDS(fixed volume and shape) Crystal – regular atomic arrangement
SOLIDS(fixed volume and shape) Glass: Atoms not periodic
Solids: Plastics Plastics: Formed from chains of molecules
LIQUIDS (fixed volume, variable shape) Liquid Crystals: Molecules line up under an electric field
PLASMA (Gas with free electrons) By far the most abundant state of matter in the universe!!!
Changes of State HYDROCARBONS
Changes of State Gas Liquid Solid How does a candle work?
Distillation (Fractionation) Column Gasoline, kerosene, diesel fuel, asphalt & tar are distilled from crude oil.
Chemical Reactions: Oxidation & Reduction Rusting = Oxidation Smelting = Reduction
Chemical Reactions: Polymerizaton & Depolymerization Addition Polymerization
Chemical Reactions: Polymerizaton & Depolymerization Condensation Polymerization
Materials and the Modern World • Materials define a society’s technical sophistication • Chemists’ contributions • Properties of materials result from: • The kind of atoms of which it is made • The arrangement of those atoms • Type of bonding between those atoms
Different Kinds of Strength • Strength • Compressive • Tensile • Shear • Elastic Limit = the breaking point • Strength depends on the types and arrangements of bonds
Compressive Strength:(Strength against squeezing) • Stack of paper • Masonry • Wood
Tensile Strength:(Strength against pulling) • Wire • Rope • Chains
Shear Strength:(Strength against twisting) • Girder network • Diamond
Composite Materials • Combination of materials increases strength • Reinforced concrete • Fiberglass • Plywood