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Phase Changes

Phase Changes. exothermic. endothermic. Phase Changes. sublimination. vaporizing. melting. solid. liquid. gas. condensing. freezing. Phase changes and their enthalpy changes. Heating Curve. Heating Curve of Water. Quantitative Aspects of Phase Changes.

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Phase Changes

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  1. Phase Changes

  2. exothermic endothermic Phase Changes sublimination vaporizing melting solid liquid gas condensing freezing

  3. Phase changes and their enthalpy changes.

  4. Heating Curve

  5. Heating Curve of Water

  6. Quantitative Aspects of Phase Changes Within a phase, a change in heat is accompanied by a change in temperature which is associated with a change in average Ek as the most probable speed of the molecules changes. q = (specific heat )(amount)(ΔT) During a phase change, a change in heat occurs at a constant temperature, which is associated with a change in Ep, as the average distance between molecules changes. q = (amount)(enthalpy of phase change or ΔH)

  7. Heats of Fusion and Vaporization

  8. Problem • How much energy is transferred when 125 g of water are converted from 25oC to 70oC? to 120oC? ΔHvap = 2.26 kJ/g ΔHfus = 0.33 kJ/g sp.htice = 2.09 J/g oC sp.htwater = 4.18 J/g oC sp.htsteam = 2.10 J/g oC

  9. Fusion Curve critical point melting freezing 1 atm Sublimation Curve vaporization triple point condensation Vapor Pressure Curve sublimation deposition Phase Diagrams Liquid Solid Pressure normal boiling pt. normal melting pt. Gas Temperature

  10. CO2 H2O Phase diagrams for CO2 and H2O.

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