Question

Use any one of the phase changes to explain what is meant by dynamic equilibrium.

Short answer

Dynamic equilibrium, as illustrated by phase change such as evaporation, refers to the state where the rate of change in one direction (e.g., liquid to gas) is balanced by the rate of change in the opposite direction (e.g., gas to liquid), causing no net change in the overall system.

Step-by-step solution

Understanding the concept of Dynamic Equilibrium

Dynamic equilibrium is a concept in physical and chemical systems where there is a balance between opposing forces or reactions. The key point is that, although there may be continual changes at a micro/individual level, there is no change at a macro/systemic level.

Explaining phase change as an example of dynamic equilibrium

Take the evaporation of water for instance. When a puddle of water is left in the sun, the water molecules gain energy and eventually become vapour, this is the forward reaction. However, at the same time some water vapour molecules will lose energy and become water again, this is the backward reaction. At some point, the rate at which water molecules are evaporating will equal the rate at which water vapour molecules are condensing. When this happens, it doesn’t mean that all reactions stop. Rather, the forward and backward reactions are still happening but at the same rate. Hence, there’s no net change and the system is said to be in dynamic equilibrium.

Recap of the exercise

To sum up, the concept of dynamic equilibrium can be well explained through the process of phase change. For instance, during the evaporation of water, the water progresses from the liquid phase to the gas phase (evaporation) and from the gas phase to the liquid phase (condensation) simultaneously. In dynamic equilibrium, the rates of these two opposing processes become equal, leading to no noticeable change in the overall system. This phenomenon where two opposing processes occur at the same rate showcases dynamic equilibrium.