Vapor Pressure The molecules at the surface can spontaneously go into a gas as KE increases enough...
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Transcript of Vapor Pressure The molecules at the surface can spontaneously go into a gas as KE increases enough...
![Page 1: Vapor Pressure The molecules at the surface can spontaneously go into a gas as KE increases enough to break attractive forces.](https://reader030.fdocuments.in/reader030/viewer/2022032803/56649e245503460f94b1300f/html5/thumbnails/1.jpg)
Vapor Pressure
• The molecules at the surface can spontaneously go into a gas as KE increases enough to break attractive forces.
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Vapor Pressure and Boiling Point
• Liquid boils when its vapor pressure equals the external pressure (atmospheric pressure) acting on the surface of the liquid.
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Quick Demo
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Phases
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Phase diagrams
• A graph showing the relationships between solid, liquid, gas, and temperature and pressure
• Normal boiling point: the temperature at which a substance boils at 1.00 atm.
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Phase Diagram Vocab• Triple Point: temperature and pressure where
solid, liquid, and gas all coexist
• Critical Point: Is it a gas or liquid – who knows?– Critical Temp- highest temp a liquid can form– Critical Press – press required for liquefaction – *** KE of molecules greater than attractive forces!
• Example: Nitrogen CT: 126.1 K, CP: 33.5 atm
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Phase DiagramsPhase diagrams display the state of a substance at various pressures and temperatures.
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Phase Diagrams• The triple point (T), the point at which all three
states are in equilibrium.
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Phase DiagramsIt ends at the critical point (C); above this critical temperature and critical pressure the liquid and vapor are indistinguishable from each other.
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Phase Diagrams• Below the triple point the substance cannot exist
in the liquid state.• Along the circled line the solid and gas phases are
in equilibrium; the sublimation point at each pressure is along this line.
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Phase Diagram of Water
• Note the high critical temperature and critical pressure.– These are due to the
strong van der Waals forces between water molecules.
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Phase Diagram of Water
• The slope of the solid-liquid line is negative.– This means that as the
pressure is increased at a temperature just below the melting point, water goes from a solid to a liquid.
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Phase Diagram of Carbon Dioxide
Carbon dioxide cannot exist in the liquid state at pressures below 5.11 atm; CO2 sublimes at normal pressures.