ENTROPY AND SPONTANEITY

• Spontaneous process


  A physical or chemical change that occurs by itself, without requiring an outside force, and continues until equilibrium is reached
• Spontaneity (in chemical reactions)

  A chemical reaction is spontaneous if it proceeds as written (from left to right) without an input of energy
• The energy change in the system cannot solely tell whether a chemical reaction will occur spontaneously. To make this kind of prediction, another thermodynamic quantity is needed: ENTROPY.
• Enthalpy


  The total measure of heat content in a system under constant pressure
• Entropy


  The measure of the level of disorder and randomness in a thermodynamic system
• Entropy


  A quantity used to describe the course of a process, whether it is spontaneous and has a probability of occurring in a defined direction, or non-spontaneous and will not proceed in the defined direction, but in the reverse direction
• SI unit of entropy: joules per Kelvin (J/K)
• How entropy changes occur


  No information provided
• ENTROPY CHANGES:

  (Process:Order-Disorder)

  
  

  Melting: Solid-Liquid

  Vaporization: LIquid- Vapor

  Dissolving: Solute-Solution

  Heating: System at T1-System at T2 (T2>T1)
• In a chemical reaction, ΔHreaction = Hproducts - Hreactants. If it is exothermic, then ΔHreaction = (-). To get a negative ΔHreaction , the Hproducts must be lower than the Hreactants.
• Heat flows from a hotter object to a colder one. An iron object rusts in moist air. Sugar dissolves in a cup of coffee.