Chemistry 15: Kinetic Theory

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Chemistry 15 Kinetic Theory

• Christopher Chui

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Molecules in Motion

• The kinetic theory is based on 3 assumptions 1)
  all matter is composed of small particles 2) the
  particles of matter are in constant motion 3)
  all collisions are perfectly elastic
• The mean free path of a molecule is the average
  distance it travels between collisions with other
  molecules
• When a gas molecule collides with the wall of a
  container, it exerts a force called pressure on
  the container
• A manometer is an instrument used to measure gas
  pressure
• Barometers are closed-arm manometers used to
  measure atmospheric pressure. 1 atm 760 mm Hg
  101.325 kPa
• 1kPa 7.50 mm Hg. 1 Pa is a pressure of 1 N/m2

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Temperature

• Temperature is a measure of the average kinetic
  energy of the particles of an object
• KE ½ mv2
• Absolute zero -273.15 oC 0 K
• According to kinetic theory, the excess kinetic
  energy of the particles in a warm object is
  passed on to the particles of a cooler object as
  they collide
• The 4 states of matter are solid, liquid, gas,
  and plasma
• Gas particles travel independently in
  straight-line paths. Gases assume the shape and
  volume of their container

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States of Matter

• Liquid particles appear to vibrate around moving
  points, but actually travel in straight-line
  paths between collisions
• Liquids have a definite volume but assume the
  shape of their containers
• Solid particles are arranged in a definite
  pattern
• Solids have both a definite shape and a definite
  volume
• The physical state of a substance depends mostly
  on the bonding in the substance
• A plasma is composed of electrons and positive
  ions at very high temperatures
• Electric and magnetic fields affect the plasma
  state
• The study of plasma is called magnetohydrodynamics
  , MHD