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🧂physical chemistry ii review

Non-equilibrium processes

Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025

Definition

Non-equilibrium processes refer to systems that are not in a state of thermodynamic equilibrium, meaning that macroscopic properties such as temperature, pressure, and chemical potential can change over time. These processes are essential for understanding fluctuations and transformations in systems where external forces or gradients drive change, which can lead to insights into molecular dynamics and energy exchanges.

5 Must Know Facts For Your Next Test

  1. Non-equilibrium processes can be driven by external forces such as temperature gradients or chemical concentration differences, leading to changes in the state of a system over time.
  2. These processes are crucial for understanding real-world phenomena like chemical reactions, phase transitions, and biological processes, where equilibrium assumptions often break down.
  3. In non-equilibrium systems, fluctuations can occur, leading to temporary deviations from average behavior, which can be quantitatively described using fluctuation theorems.
  4. The Jarzynski equality demonstrates that the work done on a system during a non-equilibrium process can provide information about the free energy changes, revealing insights into the underlying molecular mechanisms.
  5. Non-equilibrium thermodynamics introduces new concepts such as entropy production and irreversibility, highlighting how systems evolve towards equilibrium states.

Review Questions

  • How do non-equilibrium processes differ from equilibrium processes in terms of macroscopic properties?
    • Non-equilibrium processes differ from equilibrium processes in that they involve changing macroscopic properties over time, such as temperature and pressure, whereas equilibrium processes have constant properties. In non-equilibrium systems, there can be gradients or driving forces causing these changes, leading to fluctuations that are not present in equilibrium. This dynamic nature is crucial for understanding systems like chemical reactions and heat flow.
  • Discuss how the Fluctuation Theorem is applicable to non-equilibrium processes and its significance.
    • The Fluctuation Theorem is significant in non-equilibrium processes because it quantifies the likelihood of observing deviations from expected average behaviors due to fluctuations. It provides a statistical framework that links microscopic events with macroscopic thermodynamic laws, enabling us to understand how systems respond under varying conditions. This theorem is key for predicting outcomes in systems far from equilibrium, where conventional thermodynamic laws may not apply.
  • Evaluate the implications of the Jarzynski Equality for our understanding of non-equilibrium processes and their relationship with free energy changes.
    • The Jarzynski Equality has profound implications for understanding non-equilibrium processes as it reveals that even when a system undergoes work done on it in a non-equilibrium manner, we can still infer free energy differences between states. This equality emphasizes that the path taken during a transformation matters significantly and challenges traditional views of free energy being defined solely at equilibrium. By applying this relation, researchers can gain insights into molecular behavior during transitions and more accurately model complex systems.