( GENCHEM) KINETIC MOLECULAR THEORY

• Kinetic Molecular Theory of Matter


  Provides an overview of the microscopic properties of molecules or atoms and their interactions
• Kinetic Molecular Theory of Matter

  • It describes the microscopic properties of matter and how they translate to the state and other properties of matter
• What the Kinetic Molecular Theory states

  • Matter is composed of small particles
  • The molecules interact with one another through attractive forces. The strength of these forces is related to the distance between the particles
  • These molecules are always in constant random motion
  • The temperature of a substance is a measure of the average kinetic energy of the molecules
• Matter


  Composed of small particles (atoms or molecules)
• Intermolecular forces


  The attractive forces between molecules
• Stronger intermolecular forces


  Smaller distance between particles
• Solids


  • Particles have strong intermolecular forces such that their particles are very close to one another
• Liquids


  • Particles have intermediate intermolecular forces, making them farther apart compared to solids
• Gases


  • Particles have very weak intermolecular forces, making them very far apart from one another
• All molecules are in constant random motion
• The extent of molecular motion varies depending on temperature and strength of intermolecular forces
• Nanoscale representation of matter

  • molecules in ice
  • molecules in water
  • molecules in steam
• Solids


  • Particles have restricted motion, only able to vibrate back and forth around a specific point or location
• Liquids


  • Particles are able to move past each other, but motion is restricted to small distances as they will collide with another molecule
• Gases


  • Particles are able to move in relatively long distances before colliding with another molecule, due to being very far apart
• Increasing temperature


  Increases the average kinetic energy of molecules
• States of matter

  • Solid (ice)
  • Liquid (water)
  • Gas (steam)

  
• Properties of states of matter

  • Shape
  • Volume
  • Compressibility
• The state of matter is determined by temperature and strength of intermolecular forces
• Melting


  1. Molecules in ice vibrate back and forth to a specific location

  2. Increasing temperature provides enough kinetic energy to overcome strong intermolecular forces

  3. Solid becomes a liquid
• Vaporization


  1. Liquid water particles are able to move past one another in relatively longer distances

  2. Liquid is converted to a gas
• Ice-skating is possible since the molecules in ice are farther apart than they are in liquid water
• As explained by KMT:

  • At lower temperatures, intermolecular forces determine the state of a substance.  
  • Substances with intermediate to strong intermolecular forces will form a condensed phase, either solid or liquid.  
  • Those with weak intermolecular forces will be in the gaseous state.
• • Recall that a  higher temperature means a higher average kinetic energy.
  • This means that the particles will have enough energy to move around faster.

  Increasing the temperature also weakens the intermolecular forces of attraction.
• • The kinetic molecular theory of matter provides an overview of the microscopic properties of molecules or atoms and their interactions.
  • It describes the microscopic properties of matter and how they translate to the state and other properties of matter. 
• 1. .Matter is composed of small particles.
  2. The molecules interact with one another through attractive forces. The strength of these forces is related to the distance between the particles
• 1. These molecules are always in constant random motion.
  2. The temperature of a substance is a measure of the average kinetic energy of the molecules.