3.3.1 Kinetic Theory

• Kinetic Theory

  Describes how particles (atoms or molecules) move and interact in different states of matter
• States of matter

  • Gases
  • Liquids
  • Solids
• Gases

  • Particles are in constant, random motion
  • Move quickly and are spread far apart
  • Frequent collisions between particles and with the walls of the container
  • Pressure is caused by these collisions
• Liquids

  • Particles are closer together than in gases but still move around
  • Have enough energy to slide past one another
  • Have a definite volume but take the shape of their container
• Solids

  • Particles are tightly packed and vibrate in fixed positions
  • Have a definite shape and volume
  • Strong intermolecular forces keep particles in place
• Temperature

  A measure of the average kinetic energy of its particles
• Higher temperature

  Particles move faster and have more kinetic energy
• When energy is added to a substance

  Particles move faster, increasing their kinetic energy
• When energy is removed from a substance

  Particles move slower, decreasing their kinetic energy
• Pressure (for gases)


  Caused by particles colliding with the walls of the container
• Volume (for gases)

  The space that the gas occupies
• Changes in volume


  Affect pressure, especially when temperature and the number of particles are constant
• Boyle’s Law

  At a constant temperature, the pressure of a gas is inversely proportional to its volume
• Boyle’s Law formula

  P1V1=P2V2
• Charles’s Law

  At constant pressure, the volume of a gas is directly proportional to its temperature (in Kelvin)
• Charles’s Law formula

  V1/T1 = V2/T2
• Gas behavior

  • Hot Air Balloons
  • Pressure Cookers
• States of matter transitions

  • Ice to Water
  • Water to Steam
• Thermal expansion implications

  • Bridges
  • Railways
• Kinetic Theory helps explain everyday phenomena and scientific principles related to the behavior of gases, liquids, and solids