(N/A) Physical equilibrium refers to a state where the physical state of a substance changes but its chemical composition remains the same,such as $H_2O(s) \rightleftharpoons H_2O(l)$.
Chemical equilibrium refers to a state in a reversible chemical reaction where the rate of the forward reaction equals the rate of the backward reaction,and the concentrations of reactants and products remain constant,such as $N_2(g) + 3H_2(g) \rightleftharpoons 2NH_3(g)$.
Key differences include:
$1$. Physical equilibrium involves only physical changes,whereas chemical equilibrium involves chemical changes.
$2$. Physical equilibrium is established in physical processes like phase transitions or dissolution,while chemical equilibrium is established in chemical reactions.
$3$. In physical equilibrium,the chemical identity of the species is preserved,whereas in chemical equilibrium,new substances are formed.