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Pressure. 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. - PowerPoint PPT Presentation
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Pressure
• 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 TermsManometer
Pressure is defined as force per unit area.
Air is a gas...it must also be exerting pressure.
Called air pressure or atmospheric pressure.
The standard unit of atmospheric pressure (at sea level):
1 atmosphere = 760 mmHg = 101.3 kPa kilopascalsmillimeters of Mercury
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.
dynamicequilibrium
Pressure of gas at equilibrium with its liquid in a closed system is known as the vapour pressure.
characteristic physical property
A manometer measures vapour pressure.
• Compares vapour pressure to air pressure. • Measures difference in height on both sides.
IMFs determine the rate of vapourization.
Weak IMFs: more particles vapourized - higher vapour pressure – more volatile.
Heat increases particles kinetic energy - breaks IMFs.
Increases rate of vapourization - pressure increases.
Boiling Point:When vapour pressure is equal to atmospheric pressure.
(1 atmosphere, 101.3 kPa, 760 mmHg)
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.
Longer cooking time to prepare foods at higher altitudes.
At lower pressure the water boils at a lower temperature – longer cooking time.
• Standard air pressure is 101.3 kPa.
Boiling Temp
• Boil: when vapour pressure = air pressure
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 TermsManometer