Why do liquids solidify when cooled

Because when liquids are cooled the molecules slow down and that causes liquids to freeze

Because the liquid loses its kinetic energy and the particles in the liquid begin to slow down.

Kinetic energy = 1/2mv^2. since the mass is constant we can form a ratio of it's kinetic energy at 60 divided by that at 30 to see ke(60)/ke(30) = +(60^2)/30^2). this may be said to 300% increase.