spontaneous reaction - occurs w/o any outside intervention

• usually exothermic, but can also be endothermic
  • ammonium salts dissolving in water is endothermic
• DE = q + w
  • q = heat absorbed by system from surroundings
  • w = work done on surroundings by system
• reversible process - can be restored to its original state using same path
  • results in no net change in system, surroundings
  • includes all chemical systems at equilibrium
• irreversible process - can only be restored using a different path
  • different q, w values from initial process
  • includes all spontaneous reactions
• can be fast or slow

Find the conditions surrounding H2O(l) >> H2O(s)  

• temperature decreases for water to turn to ice
• energy leaves water
  • DH is negative
• product is more orderly/structured than reactant
  • DS is negative

entropy - the amount of disorder in a system

• DS = Sfinal - Sinitial
• positive value >> more disorder
• negative value >> less order
• 2nd law of thermodynamics - entropy increases for all spontaneous reactions
  • S = 0 for reversible processes
• 3rd law of thermodynamics - entropy = 0 at absolute zero (0K)
  • translational motion - entire molecule moving
  • vibrational motion - periodical mov’t to/away
  • rotational motion - spinning mov’t
  • increase temperature >> more mov’t >> more entropy
  • decrease temperature >> less mov’t >> less entropy
• Ssolid < Sliquid < Sgas
• å S = å Sproducts - å Sreactants

Arrange the following changes from least increase in entropy to greatest increase in entropy: 1g of ice warmed by 1°, 1g of ice melted, 1g of water frozen, 1g of water evaporated.  

• water to liquid is decrease in entropy
• phase changes increase in entropy more than just increasing temperature
• gas has more entropy than liquid
• 1g of water frozen, 1g of ice warmed by 1°, 1g of ice melted, 1g of water evaporated