SPONTANEITY & ENTROPY

• A process of occurs naturally.

  Spontaneous
• A process that cannot proceed unless there is a driving force or outside help.

  Non-spontaneous
• Evaporation of water at room temperature is an example of spontaneous process.
• Decay of animal wastes is an example of spontaneous process.
• Falling of a bullet that is fired upward is an example of spontaneous process.
• Boiling of waters is an example of non-spontaneous process.
• Separation of hydrogen and oxygen ions at room temperature is an example of non-spontaneous process.
• It refers when a flammable substance burns by its self even without direct application of spark or flame.

  Spontaneous Combustion
• Spontaneous combustion may occur without any intervention in a given set of conditions.
• Spontaneous combustion is an irreversible process.
• Reversible systems can go back and forth between initial and final states along the same path. For example interconversion of liquid water and ice.
• Process that are reversible are the ones that attains a state of equilibrium. Spontaneous does not implied that reaction proceeds with greater speed.
• Most exothermic reactions are spontaneous due to decrease in enthalpy.
• Spontaneous combustion is exothermic and the products has lower enthalpy than the reactants. For example, a coffee left to cool down.
• Melting of ice, vaporation of alcohol and acetone, are example of endothermic processes that happen spontaneously.
• Spontaneity also depends on temperature.
• It refers to the natural tendency for all matter and energy in the universe, is to evolve towards a more disorderly state.

  Entropy
• Entropy measures the state of randomness.
• Entropy also measure how much energy is unavailable for conversion into work.
• Entropy is a state function, independent of the path or the route taken in attaining the final state.
• The symbol for change in entropy is ∆S
• A positive value of ∆S, indicates that the final state is more disordered than the initial state (high entropy).
• A negative value of ∆S, indicates that the final state is more ordered than the initial state (low entropy).
• Spontaneity depends on both enthalpy and entropy.
• Entropy increases if solid is converted into gas which means particles are more scattered and are no longer confined.

  Change in phase
• Lowering the temperature will also decreasing the kinetic energy, hence less random ; meanwhile, rising the temperature will also increase the kinetic energy, hence more random.

  Change in temperature
• The possible positions of the particles increases the number of particles increases.

  Number of particles
• Lowering the temperature will also decreasing the kinetic energy, hence less random ; meanwhile, rising the temperature will also increase the kinetic energy, hence more random.

• Entropy increases if solid is converted into gas which means particles are more scattered and are no longer confined.

• A tool used to measure and entropy change.

  Calorimeter
• The entropy of 1 mole of a substance at standard condition, 25°C and 1 atm pressure.

  Standard Molar Entropy
• The symbol for standard molar entropy is S°
• It states that natural processes proceed in the direction that maintains or increase the total entropy of the universe, and in any spontaneous change, there is a net increase in entropy.

  Second Law Thermodynamics
• This states that a perfect crystal has zero entropy at absolute zero.

  Third Law of Thermodynamics
• Significance of the Second Law Thermodynamics:

  • Why things work as they do?
  • Why gasoline makes the engine run?
  • Why hot pans cool down?
  • Why our bodies remains warm even when it is cold?