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Changes of State

Changes of State. Melting point. As the temp of the solid is increased, a point is eventually reached where the liquid and solid have identical vapor pressures. Vapor pressure of solid and liquid water as a function of temperature. Normal melting pt.

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Changes of State

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  1. Changes of State

  2. Melting point • As the temp of the solid is increased, a point is eventually reached where the liquid and solid have identical vapor pressures

  3. Vapor pressure of solid and liquid water as a function of temperature

  4. Normal melting pt • The temp at which the solid and liquid states have the same vp under the conditions where the total pressure is 1 atm

  5. Normal boiling pt • Temperature at which the vp of the liquid is exactly 1 atm • boiling occurs when the vp of the liq is equal to the pressure of its environment

  6. PHASE DIAGRAMS

  7. Phase Diagrams • Represent the phases of a substance as a function of temperature and pressure

  8. Phase Diagrams • Shows which state can exist at given temp and pressure • conditions of CLOSED system

  9. Critical temp • temp above which vapor cannot be liquified no matter what pressure is applied

  10. Critical Pressure • Pressure required to produce liquification at the critical temp

  11. Critical point • Defined by critical pressure and temp (374oC, 218 atm) • beyond this point is intermediate “fluid” region

  12. Phase diagram for water • Solid/liquid line has negative slope • mp of water decreases as external pressure increases

  13. Phase diagram for water • Opposite of most substance b/c density of ice less than water at mp

  14. Phase diagram for CO2 • Solid/liquid line has positive slope • solid CO2 is more dense than liquid CO2

  15. Phase diagram for CO2 • Triple point at 5.1 atm and -56.6oC • Critical point at 72.8 atm and 31oC • at 1 atm CO2 sublimes

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