Movement of molecules depend on the viscosity of the medium and kinetic energy.
Water in a freezer are in hard form so the molecules are in rest form due to hard medium and no kinetic energy. Due to this hard medium, freedom of movement of water molecules are not possible so they remain in static position.
While on the other hand, water on a stove are in liquid form in which molecules are moving continuously because temperature of water increases which increases the kinetic energy of the water molecules. This high kinetic energy allows the molecules of freedom of movement in the medium.
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