CHAPTER 10 STATES OF MATTER

liquid solid gas Kinetic vs. Potential energy Which state of matter has the greatest KE?

KINETIC THEORY Particles are small hard spheres, with insignificant volume, mostly empty space, no attractive or repulsive forces Particles in constant and rapid motion (speed in excess of 1700 km/hr at room temp) All collisions are perfectly elastic

GAS PRESSURE Definition-FORCE exerted by gas molecules PER UNIT SURFACE AREA VACUUM-no particles, no pressure ATMOSPHERIC PRESSURE Decreases as altitude increases Collisions decrease as pressure decreases

MEASURING PRESSURE Barometer is common device used to measure pressure SI unit of pressure is kPa-KILOPASCAL Other units equal to 101.3 kPa 1 atmosphere (atm) 760 mm Hg 30 inches Hg 760 torr Distinguish between using aneroid vs. mercury barometer.

KINETIC ENERGY AND KELVIN TEMPERATURE TEMPERATURE IS A MEASURE OF THE AVERAGE KINETIC ENERGY Increase KE, increase temp Decrease KE, decrease temp Absolute zero—0 K, or oC

Particles must have sufficient KE to overcome the intermolecular forces

EVAPORATION Definition-conversion at the surface of a liquid to a gas or vapor at a temperature below the boiling point To evaporate molecules must have a certain minimum kinetic energy to overcome attractive forces Cooling process

Liquid Gas At equilibrium rate of evaporation =rate of condensation

VAPOR PRESSURE High vapor pressure vs. low vapor pressure Easily goes up into vapor Difficult to go up into vapor

BOILING POINT The temperature at which the vapor pressure of the liquid is just equal to the external pressure Boiling point decreases as pressure decreases

SOLIDS melting Solid Liquid freezing

IONIC VS. MOLECULAR Which one has a higher melting point? NaCl vs. H2O 801 oC 0 0C What is the freezing point of water?

Buckminsterfullerene Aka: Buckeyball

Phase Diagram of Water

The phase diagram for carbon dioxide. Sublimation: solid to gas