Describe the change in entropy for a given system over time.

• The second law of thermodynamics states that the total entropy of an isolated system can never decrease and is constant only when all processes the system undergoes are reversible.
• Entropy can be qualitatively described as the tendency of energy to spread or the unavailability of some of the system’s energy to do work.
• Localized energy will tend to disperse and spread out.
• Entropy is a state function and therefore only depends on the current state or configuration of a system, no how the system reached that state.
• Maximum entropy occurs when a system is in thermodynamic equilibrium.
• The change in a system’s entropy is determined by the system’s interactions with its surroundings.
• Isolated systems spontaneously move toward thermodynamic equilibrium.
• The entropy of an isolated system never decreases, but the entropy of a closed system can decrease because energy can be transferred into or out of the system.

Only qualitative treatment of the second law of thermodynamics is within the scope of AP Physics 2.

More videos

More videos

Simulation page: Gas Properties

Simulation page: Energy Forms and Changes