 Gases consist of tiny particles (atoms or molecules) traveling in straight-line motion.  The molecules in a gas occupy no volume.  The particles are in constant random motion.  Pressure exerted by a gas comes from the particles colliding with a surface  The particles are assumed to neither attract nor repel each other.  The average kinetic energy of the gas particles is directly proportional to the Kelvin temperature of the gas.

 Unit of temperature based on an absolute scale  0 K = absolute zero = all molecular motion ceases  o C = _____ K  K – 273 = ______ o C

 Convert from Celsius to Kelvin  25 0 C = ______ K  C = _____ K  Convert from Kelvin to Celsius  500 K = _____ o C  50 K = ______ o C

 Increase temperature = __________ kinetic energy  Decrease temperature = __________ kinetic energy  KE = ½ mv 2  KE = Kinetic Energy  m = mass  v = velocity

 Names of phase changes  Solid  Liquid :  Liquid  Solid :  Liquid  Gas :  Gas  Liquid :  Solid  Gas :  Gas  Solid :

 Triple Point – The temperature and pressure at which all three phases (solid, liquid, gas) are occurring simultaneously.  Critical Point – The temperature and pressure above which liquid and gas no longer exist as separate phases (above this, its is a “supercritical fluid”) TOA

 Normal Melting Point – temperature at which a substance melts (or freezes) at standard pressure (1 atm)  Normal Boiling Point – temperature at which a substance boils (or condenses) at standard pressure (1 atm)