Chapter 13.2 States of Matter, The nature of liquidsThe particles in a liquid have an attraction for each other. The kinetic energy in them cannot overcome this attraction

VolumeThe particles of a liquid or solid are touching. It is basically impossible to compress them very much (Don’t bring up that Black Hole and neutron star stuff, this is chemistry, not physics)

What is the difference between liquids and gases? Theoretically, there are no attractions

between particles in a gas, but there are in a liquid.

What are these attractions called?

Van der Waals forces or Intra molecular forces London dispersion, for instance

Evaporation Molecules with enough kinetic energy

can escape the liquid’s surface. Since they have more energy than the ones left behind, it would tend to cool the liquid.

Vapor Pressure Vapor pressure is the pressure exerted

by a gas above a liquid in a sealed container.

More heat = more vapor pressure Past boiling point is more vapor pressure Measured by a manometer (see

illustration p 393 in book)

Manometer measures vapor pressure

Boiling point When the particles throughout the liquid

have enough energy to become vapor Or The temperature at which the vapor

pressure is equal to the external pressure

Boiling point and pressure Since the boiling point is when the vapor

pressure is equal to the external pressure if there is less external pressure, the boiling point is lower (such as when you are high in the mountains)

Water

Key Concept Questions