9.6 Probability, Thermal Equilibrium, and Entropy

• Probability is a fundamental concept in thermodynamics, which is a statistical science
• Are probabilities in statistical probability exact or approximate?

  Approximate
• What is a condition for thermal equilibrium?

  No net heat transfer
• Match the state of a system with its entropy:

  Orderly State ↔️ Low Entropy

  Disorderly State ↔️ High Entropy
• What type of energy prevents temperature-driven heat transfer in thermal equilibrium?

  Thermal energy
• What is entropy a measure of within a system?

  Disorder or randomness
• What does a higher entropy indicate about the degree of disorder in a system?

  Greater disorder
• Higher entropy states correspond to more probable states.
• In thermodynamics, what are we concerned with regarding probability?

  State of the system
• What fundamental principle connects probability and entropy?

  Higher entropy states are more probable
• When objects in thermal contact cease to exchange heat, they have reached the same temperature
• Entropy is a measure of the disorder or randomness
• The Second Law of Thermodynamics states that in an isolated system, entropy will always increase
• Arrange the following states in order of increasing entropy:

  1️⃣ Ordered crystal

  2️⃣ Liquid water

  3️⃣ Steam
• Why are higher entropy states more probable than lower entropy states?

  More disordered arrangements
• What are the units of entropy change (ΔS)?

  J/K
• Entropy change is measured in units of J/K
• The magnitude of the entropy change depends on the amount of heat transfer and the temperature.


  True
• What is the formula for calculating entropy change?

  ΔS = Q/T
• Calculate the entropy change when 500 J of heat is added to a system at 300 K.

  1.67 J/K
• Entropy decreases when heat is removed
• A negative ΔG indicates a spontaneous reaction.
• Match the property with its definition:

  Gibbs Free Energy ↔️ H - TS

  Enthalpy ↔️ Total energy of the system

  Entropy ↔️ Measure of disorder

  Temperature ↔️ Hotness or coldness of the system
• The Second Law of Thermodynamics states that entropy in an isolated system always increases.

  True
• What type of events does classical probability deal with?

  Deterministic
• Statistical probability applies to large-scale systems.
• Uniform temperature prevents temperature-driven heat transfer.
• In irreversible processes, entropy always decreases.

  False
• In thermal equilibrium, there is no net transfer of heat
• In irreversible processes, entropy always increases
• Melting ice increases entropy because the water molecules become more randomly arranged.


  True
• Match the entropy state with its description:

  Low Entropy ↔️ Molecules in a uniform arrangement

  High Entropy ↔️ Molecules in a random arrangement
• Classical probability deals with deterministic events.
• Thermal equilibrium occurs when two objects in thermal contact cease to exchange heat.
• Objects in thermal equilibrium must have no net transfer of heat between them


  True
• Breaking a glass is an example of an increase in entropy


  True
• Higher entropy indicates a greater degree of energy dispersion


  True
• Entropy is low in ordered states and high in disordered states


  True
• Spontaneous processes always increase the overall entropy of an isolated system


  True
• Entropy decreases when heat is added to a system

  False