1. 13.2 The Nature of Liquids

2. Describe the particles in a liquid

3. Liquid particles are attracted to each other
13.2 The Nature of Liquids
Liquid particles are attracted to each other
The particles in a gas are not

4. Intermolecular Forces
Dipole-Dipole
Dispersion
Hydrogen Bonds

5. Dipole – Dipole Forces

6. London Dispersion Forces

7. Hydrogen Bonding

8. Particles of a liquid spin and vibrate while they move, adding to their average kinetic energy
Most of the particles do not have enough energy to escape into the gaseous state; must overcome their intermolecular attractions

9. The intermolecular attractions reduce the amount of space between particles of a liquid
Liquids are more dense than gases
Increasing pressure on liquid has hardly any effect on it’s volume

10. Vaporization -the conversion of a liquid to a gas or vapor
Evaporation -when this occurs at the surface of a liquid that is not boiling
Some of the particles break away and enter the gas or vapor state; but only those with certain minimum kinetic energy escape from the surface of the liquid

11. Why does a liquid evaporate faster when heated?
Explain how evaporation is a cooling process
What about the particles left behind?

12. Evaporation of a liquid in a closed container
Fig. 13.6b on page 391 shows that no particles can escape into the outside air
When some particles do vaporize, these collide with the walls of the container producing vapor pressure

13. A measure of the force exerted by a gas above a liquid is called the vapor pressure.

14. Dynamic equilibrium
Rate of evaporation = rate of condensation

15. An increase in temperature of a contained liquid increases the vapor pressure
the particles have an increased kinetic energy, and more minimum energy to escape

16. Boiling Point (bp)
The temperature at which the vapor pressure of the liquid is just equal to the external pressure on the liquid

17. Since the boiling point is where the vapor pressure equals external pressure, the bp changes if the external pressure changes
Normal boiling point- the bp of a liquid at a pressure of kPa (or standard pressure)

18. Water boils at 100° C
in Denver = ?
Denver is 1600 m above sea level and average atmospheric pressure is about 85.3 kPa