CHAPTER 16 Solids and Liquids 16.1 The Properties of Solids

Macroscopic physical properties ultimately come from the microscopic world of molecules and chemistry

Physical properties Density The amount of matter per unit volume Example: Steel has a density of 7.8 g/cm3 whereas polyethylene plastic has a density of 2 g/cm3

Density The density of a substance is affected by two factors: 1) the mass of the molecules or atoms of which the substance is made Atomic weight of platinum (Pt): 195 g/mole Molecular weight of polyethylene: >200,000 g/mole

Density The density of a substance is affected by two factors: 1) the mass of the molecules or atoms of which the substance is made Atomic weight of platinum (Pt): 195 g/mole Molecular weight of polyethylene: >200,000 g/mole 2) how closely the atoms or molecules are packed together

Density The density of a substance is affected by two factors: 1) the mass of the molecules or atoms of which the substance is made Atomic weight of platinum (Pt): 195 g/mole Molecular weight of polyethylene: >200,000 g/mole 2) how closely the atoms or molecules are packed together

Density The density of a substance is affected by two factors: 1) the mass of the molecules or atoms of which the substance is made Atomic weight of platinum (Pt): 195 g/mole Molecular weight of polyethylene: >200,000 g/mole 2) how closely the atoms or molecules are packed together Polyethylene has a lower density than platinum

Physical properties Hardness Density The resistance of a material to small deformation, like scratches Example: Glass is harder than copper, and copper is harder than plastic

Hardness How easy is it to deform a material by moving molecules out of their places? Diamond is the hardest known substance The only thing that can cut a diamond is another diamond! Diamond is a network covalent substance

Hardness The Mohs hardness scale is a scale used for describing hardness Deformation per unit force Mohs hardness scale

Physical properties Elasticity Density Hardness The ability to stretch and rebound without breaking Example: Rubber is often very elastic, and glass is hardly elastic at all

Physical properties Transparency Density Hardness Elasticity The ability for light to pass through a material Example: Glass and plastic can be transparent, whereas rubber and metals are typically opaque

Physical properties Strength Density Hardness Elasticity Transparency The amount of force a material can withstand before breaking Example: Steel is much stronger than aluminum, and aluminum is stronger than rubber or plastic

Strength Strength has three primary aspects: 1) How much will a material deform under a given force? Elastic materials such as rubber and soft plastics can deform under a great deal under a relatively small pressure

Strength Strength has three primary aspects: 1) How much will a material deform under a given force? 2) Does a material stretch before breaking or does it snap suddenly?

Strength Strength has three primary aspects: 1) How much will a material deform under a given force? 2) Does a material stretch before breaking or does it snap suddenly? Metals are typically ductile. Gold can be hammered into very thin sheets without breaking Ceramic and glass are brittle materials. So are ionic solids, including most mineral crystals and rocks

Strength Strength has three primary aspects: 1) How much will a material deform under a given force? 2) Does a material stretch before breaking or does it snap suddenly? 3) How much force can a material ultimately withstand before it breaks? Most materials will stretch a certain amount, then snap

Physical properties Electrical conductivity Density Hardness Elasticity Transparency Strength Electrical conductivity Copper wire (conductor) Plastic (insulator) The ability for electrical current to flow through a material Example: Copper and aluminum are excellent conductors, but glass, rubber, and plastic are insulators

Physical properties Thermal conductivity Density Hardness Elasticity Transparency Strength Electrical conductivity Thermal conductivity The ability for heat to flow through a material Example: Metals are good heat conductors; rubber and plastics are moderate heat conductors

Macroscopic physical properties come from the microscopic world of molecules and chemistry Density Hardness Elasticity Transparency Strength Electrical conductivity Thermal conductivity Diamond is a network covalent substance