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PHYSICAL PROPERTIES. Properties that can be measured without changing the identity of the substance. BP, FP, (Fig 2.2) color, hardness, conductivity, solubility, density = mass/volume = m/V = g/cm 3. PHASE CHANGES. Boiling: liquid gas Every substance has a specific boiling point
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PHYSICAL PROPERTIES • Properties that can be measured without changing the identity of the substance. • BP, FP, (Fig 2.2) color, hardness, conductivity, solubility, density = mass/volume = m/V = g/cm3
PHASE CHANGES • Boiling: liquid gas • Every substance has a specific boiling point • T < BP, substance = liquid; T > BP, substance = gas • As temp increases, vapor pressure above liquid increases. At the BP, ℓ g is rapid and complete. • We define BP as temp at which the vapor pressure of the gas above the liquid is equal to the atmospheric pressure (atm P); Fig 2.9 • Therefore, the BP depends on atm P (e.g. baking instructions at high elevations require more time) • Condensation: gas liquid
EVAPORATION • Evaporation occurs when molecules at the surface of a liquid escapes into the air because it has enough velocity to overcome attractive forces in the liquid. • Evaporation occurs when T < BP • In a open container, all of the liquid will evaporate • In a closed container, an equilibrium is established between ℓ and g. Fig 2.8
OTHER PHASE CHANGES • Freezing (ℓ s) & Melting (s ℓ) • Sublimation (sg) & Deposition (gs) • At FP, ℓ s; two phases are in equilibrium with each other; dynamic equil. OTHER PHYSICAL CHANGES • Solubility involves the dissolution of one substance in another to form a homogeneous solution