1. AIM # 2: How does temperature affect the vapor pressure of a liquid?

3. Vaporization: Liquid to Gas

4. Condensation: Gas to Liquid

5. 1. DYNAMIC EQUILIBRIUM
FIGURE # 1
FIGURE #2
FIGURE # 3

6. Molecules are constantly changing phase: “Dynamic”
Rate of Vaporization = Rate of Condensation
Molecules are constantly changing phase: “Dynamic”
The amount of liquid and vapor remains constant: “Equilibrium”

7. 2. The gas that is above the liquid is called its vapor and it creates a pressure called vapor pressure.

8. 3. The boiling Point of a Liquid
The boiling point (bp) is the temperature at which the vapor pressure of the liquid is just equals the atmospheric pressure.
VAPOR PRESSURE = ATMOSPHERIC PRESSURE

9. 4. See Table A: Units for Pressure at STP

12. 5. Factors That Affect Equilibrium Vapor Pressure (Table H)
A. Temperature B. Intermolecular forces

13. A. The vapor pressure of a liquid varies with its temperature

14. The vapor pressure is relatively high when the evaporation rate is high. As the temperature of a given liquid increases, so does its rate of evaporation and so does its vapor pressure

15. B. The stronger the forces between the particles the higher the boiling point.

16. In CO2(s) the intermolecular forces are weak
In CO2(s) the intermolecular forces are weak. Therefore, vapor pressure is high

17. Nonburning Dollar Bill

18. See Table H
Intermolecular attraction are strongest in ethanoic acid (acetic acid), next strongest in water, third strongest in ethanol and weakest in propanone. Thus, we can use vapor pressures as indications of relative strengths of the attractive forces in liquids.

19. In H2O (s) intermolecular forces are strong
In H2O (s) intermolecular forces are strong. Therefore, vapor pressure is low

21. What property of ethyl alcohol makes it volatile?
So ethanol is volatile, because it is a small and light molecule. The intermolecular forces are weak

22. Volatile (Table H)
A liquid with a high vapor pressure at a given temperature is said to be volatile.

23. Volatile?
Readily vaporizing at a relatively low temperature.

24. Why is the boiling point lower in Denver, CO than in San Francisco, CA??

25. Denver is at a higher altitude where the atmospheric pressure will be lower. Therefore the vapor pressure will be lower.

26. The liquid boils at lower temperature
The normal boiling point of water is 100oC. The term normal refers to standard pressure kPa.
LOCATION
PRESSURE
BOILING POINT OF WATER
SEA LEVEL
101.3 KPa
100 ºC
MT. EVEREST
34 kPa
70 ºC
The liquid boils at lower temperature

28. At high altitudes (up in the Mountains) the air pressure is less than at sea level. Thus, water will boil at a lower temperature (the vapor pressure needed to support a bubble is lower at high altitude). Therefore, cooking times are longer for things that need to be boiled (e.g. boiled eggs take longer to cook at high altitudes).

29. Changing the Boiling Point
Raise the external pressure (Use a pressure cooker)
Raises the vapor pressure needed.
Harder to make bubbles
Raises the boiling point.
Food cooks faster.

30. Highest 10 Mountains in the world
Mountain peak
Range
Location
Height (m)
Everest
Himalayas
Nepal/Tibet
8,850 K2
Karakoram
Pakistan/China
8,611
Kanchenjunga
India/Nepal
8.586
Lhotse I
8,516
Makalu I
8,463
Cho Oyu
8,201
Dhaulagiri
Nepal
8,167
Manaslu I
8,163
Nanga Parbat
Pakistan
8,125
Annapurna
8,091

31. END OF THE SHOW!