Question

why is physical equilibrium called dynamic equilibrium?

Answer 1

A state of dynamic equilibrium exists when a reversible reaction ceases to change its ratio of reactants/products, but the forward and backward reactions progress at an equal rate, meaning there is no net change. A physical equilibrium like between a solid and liquid at freezing point, the melting of solid into liquid occurs at the same rate as the freezing of the liquid into solid. There is thus no net change and the ratio of solid to liquid form remains the same.