The difference between equilibrium and steady state is subtle but important, especially in chemistry and biology:
1. Equilibrium
- Occurs in a closed system where no material enters or leaves.
- The forward and reverse processes happen at the same rate, so there is no net change in the concentrations of reactants and products.
- No energy input is needed to maintain equilibrium.
- Example: In a sealed container, a reaction between nitrogen and hydrogen forming ammonia eventually reaches equilibrium.
2. Steady State
- Occurs in an open system where substances can enter or leave.
- Concentrations remain constant over time, but reactions are ongoing and may require continuous energy input.
- The system is not at thermodynamic equilibrium; energy flow maintains the steady state.
- Example: In living cells, glucose is continuously metabolized and ATP is produced, but the overall concentrations of metabolites remain roughly constant.
In short:
- Equilibrium = no net change, no energy needed, closed system.
- Steady state = constant concentrations, energy required, open system.