22.4 Entropy

• Energy has a natural tendency to spread out rather than be concentrated in one place
• Entropy is the measure of the dispersal of energy in a system
• The greater the entropy

  • the greater the dispersal of energy
  • the greater the disorder
• Standard entropy is the entropy content of one mole of a substance under standard conditions
• When a system changes to become more random

  • energy is more spread out
  • entropy change is positive
• As a substance changes state from solid->liquid->gas

  • particles are arranged more randomly
  • energy becomes more spread out
  • entropy increases and entropy change is positive
• An increase in the moles of gaseous molecules increases the entropy
• A decrease in the moles of gaseous molecules decreases in entropy
• Standard entropies can be used to calculate the entropy change of a reaction

  • Sum of entropy products - sum of entropy reactants