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Published byBrianna Hawkins Modified over 9 years ago
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Pressure
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Define vapour pressure. Include: volatility, dynamic equilibrium Define normal boiling point in terms of vapour pressure. Interpolate and extrapolate information from pressure versus temperature graphs. Additional KEY Terms Manometer
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Pressure is defined as force per unit area. Air is a gas...it must also be exerting pressure. Called air pressure or atmospheric pressure.
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The standard unit of atmospheric pressure (at sea level): 1 atmosphere = 760 mmHg = 101.3 kPa kilopascals millimeters of Mercury
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Closed system (constant temperature) As liquid continues to vaporize, a point is reached: For every molecule that vapourizes, one condenses When vapourization = condensation we have reached equilibrium.
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dynamic equilibrium
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The pressure of a gas at equilibrium with the liquid in a closed system is known as the vapour pressure. characteristic physical property
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A manometer measures vapour pressure. Compares vapour pressure to air pressure. Measures difference in height on both sides.
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IMFs determine the rate of vapourization. Weak IMFs: more particles vapourized - higher vapour pressure – more volatile.
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Heat increases particles kinetic energy - breaks IMFs. Increases rate of vapourization - pressure increases.
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Boiling Point: When vapour pressure is equal to atmospheric pressure. Particles must have: Energy to break IMFs Energy to push out of the liquid and through the air. (1 atmosphere, 101.3 kPa, 760 mmHg)
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Any change in air pressure will produce a change in the boiling point. Particles with strong IMFs require more energy (higher temperatures) to phase change to a gas with enough pressure to equal atmospheric pressure.
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Longer cooking time to prepare foods at higher altitudes. At lower pressure the water boils at a lower temperature – longer cooking time.
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Standard air pressure is 101.3 kPa. Boiling Temp Boil: when vapour pressure = air pressure
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CAN YOU / HAVE YOU? Define vapour pressure. Include: volatility, dynamic equilibrium Define normal boiling point in terms of vapour pressure. Interpolate and extrapolate information from pressure versus temperature graphs. Additional KEY Terms Manometer
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