thermodynamics

• Thermodynamics


  The science of energy that concerned with the ways in which energy is stored within the body
• Energy transformations mostly involve heat and work movements
• Conservation of energy principle


  Energy cannot be created nor destroyed, but can only be transformed from one form to another
• System


  A quantity of matter or a region in space chosen for study
• Surroundings


  The mass or region outside the system
• Boundary


  The real or imaginary surface that separates the system from its surroundings
• Isolated system


  • Neither mass nor energy can cross the selected boundary
  • Example: coffee in a closed well-insulated thermos bottle
• Closed system


  • Only energy can cross the selected boundary
  • Example: a tightly capped cup of coffee
• Open system


  • Both mass and energy can cross the selected boundary
  • Example: an open cup of coffee
• Property of a system

  A measurable characteristic of a system that is in equilibrium
• Intensive property


  Independent of the amount of mass (e.g. temperature, pressure, density)
• Extensive property


  Varies directly with the mass (e.g. mass, volume, energy, enthalpy)
• Entropy


  A measure of the "disorder" of a system, referring to the number of different microscopic states a system can be in
• Entropy


  • A thermodynamic property - a quantitative measure of disorder
  • Traces its origin to molecular movement interpretation by Rudolf Clausius in 1850
  • Associated with heat and temperature
  • Can be visualized due to processes like expansion, heating, mixing and reaction
• Types of disorder


  • Positional disorder
  • Vibrational disorder (thermal disorder)
  • Configurational disorder
• Le Chatelier's Principle (1884)


  When a system at equilibrium is subjected to stress, the system will adjust to relieve the stress and return to equilibrium
• Factors that Affect Equilibrium


  • Concentration Stress
  • Temperature Stress
  • Volume or Pressure
• Concentration Stress


  1. Stress: a change in concentration or products of reactants by adding or removing

  2. Adjustment: change in collision rate and redistribution of particles

  3. Add - system shifts to use it up

  4. Remove - system shift to make more
• Temperature Stress


  1. Endothermic: collision reversed favored

  2. Exothermic: collisions forward favored
• Volume or Pressure


  • Pressure changes only affects equilibrium systems with unequal moles of gaseous reactants and products
  • Volume stress - changing the pressure of a system only affects these equilibria with gaseous reactants and or products