Explain solid-liquid equilibrium by giving an example.

Ice and water kept in a perfectly insulated thermos flask at $273 \ K$ and $1 \ atm$ atmospheric pressure are in an equilibrium state,and the system shows the following:
$H_2O_{(s)} \overset{1 \ atm, 273 \ K}{\rightleftharpoons} H_2O_{(l)}$ (Eq.-$i$)
The mass of ice and water does not change with time,and the temperature remains constant. However,the equilibrium is not static. Intense activity can be noticed at the boundary between ice and water. Molecules from the liquid water collide against the ice and adhere to it,and some molecules of ice escape into the liquid phase. There is no change in the mass of ice and water,as the rates of transfer of molecules from ice into water and the reverse transfer from water into ice are equal at atmospheric pressure and $273 \ K$.
$(i)$ Both the opposing processes occur simultaneously: $(H_2O_{(s)} \rightarrow H_2O_{(l)}$ and $H_2O_{(l)} \rightarrow H_2O_{(s)})$.
$(ii)$ Both processes occur at the same rate so that the amount of ice and water remains constant. If the rate of $H_2O_{(s)} \rightarrow H_2O_{(l)}$ is $r_1$ and the rate of $H_2O_{(l)} \rightarrow H_2O_{(s)}$ is $r_2$,then $r_1 = r_2$ for $H_2O_{(s)} \rightleftharpoons H_2O_{(l)}$.