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Pressure. Define vapour pressure. Include: volatility, dynamic equilibrium Define normal boiling point in terms of vapour pressure. Interpolate and extrapolate.

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Presentation on theme: "Pressure. Define vapour pressure. Include: volatility, dynamic equilibrium Define normal boiling point in terms of vapour pressure. Interpolate and extrapolate."— Presentation transcript:

1 Pressure

2 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

3 Pressure is defined as force per unit area. Air is a gas...it must also be exerting pressure. Called air pressure or atmospheric pressure.

4 The standard unit of atmospheric pressure (at sea level): 1 atmosphere = 760 mmHg = 101.3 kPa kilopascals millimeters of Mercury

5 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.

6 dynamic equilibrium

7 The pressure of a gas at equilibrium with the liquid in a closed system is known as the vapour pressure. characteristic physical property

8 A manometer measures vapour pressure. Compares vapour pressure to air pressure. Measures difference in height on both sides.

9 IMFs determine the rate of vapourization. Weak IMFs: more particles vapourized - higher vapour pressure – more volatile.

10 Heat increases particles kinetic energy - breaks IMFs. Increases rate of vapourization - pressure increases.

11

12 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)

13 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.

14 Longer cooking time to prepare foods at higher altitudes. At lower pressure the water boils at a lower temperature – longer cooking time.

15 Standard air pressure is 101.3 kPa. Boiling Temp Boil: when vapour pressure = air pressure

16 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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