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Great Ideas in Science: Lecture 6 – Properties of Materials

This lecture explores the properties of materials, including chemical bonding, states of matter, changes of state, strength, magnetic properties, and electrical properties. It delves into the different types of bonding, such as ionic, metallic, and covalent bonding, and discusses the importance of properties in defining a society's technical sophistication. Additionally, it covers the magnetic and electrical properties of materials, including conductors, insulators, and semiconductors.

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Great Ideas in Science: Lecture 6 – Properties of Materials

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  1. Great Ideas in Science:Lecture 6 – Properties of Materials Professor Robert Hazen UNIV 301 KEY IDEA: Properties of materials depend on their atoms, and how those atoms are linked together

  2. Tonight’s Outline • Review Chemical Bonding • Chemical Reactions • Properties of Materials • States of matter • Changes of state • Strength of materials • Magnetic properties • Electrical properties

  3. 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 bond 3. Ionic, metallic and covalent bonds

  4. Ionic Bonding

  5. Ionic Bonding Ionic Bonding Na Cl

  6. Ionic Bonding

  7. Ionic Bonding Mg + 2Cl MgCl2 Mg + 2Cl

  8. Ionic Bonding

  9. Metallic Bonding

  10. Metallic Bonding

  11. Covalent Bonding

  12. Covalent Bonding Hydrogen

  13. Covalent Bonding

  14. Covalent Bonding WATER

  15. Covalent Bonding

  16. 1 C 4 2 3 (R)-enantiomer Covalent Bonding: Carbon CARBON BONDING Organic Chemistry

  17. 1 C 4 2 3 (R)-enantiomer Covalent Bonding: Carbon CARBON BONDING Organic Chemistry

  18. States of Matter

  19. SOLIDS(fixed volume and shape) Crystal – regular atomic arrangement

  20. SOLIDS(fixed volume and shape) Glass: Atoms not periodic

  21. Glass vs. Crystal Structure

  22. Solids: Plastics Plastics: Formed from chains of molecules

  23. Plastic Recycling

  24. LIQUIDS (fixed volume, variable shape)

  25. LIQUIDS (fixed volume, variable shape) Liquid Crystals: Molecules line up under an electric field

  26. GAS (variable volume and shape)

  27. PLASMA (Gas with free electrons) By far the most abundant state of matter in the universe!!!

  28. Changes of State HYDROCARBONS

  29. Distillation (Fractionation) Column Gasoline, kerosene, diesel fuel, asphalt & tar are distilled from crude oil.

  30. Chemical Reactions: Oxidation & Reduction

  31. Chemical Reactions: Oxidation & Reduction Rusting = Oxidation Smelting = Reduction

  32. Chemical Reactions:Acid & Base Reactions

  33. Chemical Reactions: Polymerizaton & Depolymerization Addition Polymerization

  34. Chemical Reactions: Polymerizaton & Depolymerization Condensation Polymerization

  35. Materials and the Modern World • Materials define a society’s technical sophistication • Chemists’ contributions • Properties of Materials • The kind of atoms of which it is made • Arrangement of atoms • Type of bonding of atoms

  36. Different Kinds of Strength • Strength • Compressive • Tensile • Shear • Elastic Limit • Strength depends on the types and arrangements of bonds

  37. Compressive Strength:(Strength against squeezing) • Stack of paper • Masonry • Wood

  38. Tensile Strength:(Strength against pulling) • Wire • Rope • Chains

  39. Shear Strength:(Strength against twisting) • Girder network • Diamond

  40. Composite Materials • Combination of materials increases strength • Reinforced concrete • Plywood • Fiberglass

  41. Magnetic Properties of Materials • Magnetic field • Due to electrical current • Electrons spinning • Arrangement of atomic magnets • Degree of alignment determines the strength of magnetism

  42. Key Idea Modern electronics control the flow of electrons • Metals are conductors of electricity, while ionic and covalently-bonded materials are electrical insulators • Semiconductors conduct electricity under carefully controlled conditions Key Words p-type and n-type diode integrated circuit microchip

  43. Conductors & Insulators • Electrical conductors allow electrons to flow freely. • Electrical resistors drain some energy from an electrical current. • Electrical insulators prevent the flow of electricity.

  44. Semiconductors • Semiconductors: neither good conductors nor insulators • Example: Silicon

  45. Semiconductors: Phosphorus doped

  46. n-type Semiconductors Dope with phosphorus One extra electron for each P

  47. Semiconductors: Aluminum doped

  48. p-type Semiconductors Dope with aluminum A missing electron = hole

  49. p-type Semiconductors Dope with aluminum A missing electron = hole

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