why is density of water maximum at 4 degree celsius?

The hydrogen bonds in water keep on forming and breaking.Due to hydrogen bonding, gaps are introduced in the structure of water and various structural units are formed.As the temperature is raised from 0 degrees Celsius, more hydrogen bonds break than form and thus the structural units collapse.This results in the filling of gaps in the water by smaller structural units or molecules which in turn increases the density of water.As the temperature is further increased the smaller structural units and molecules acquire speed and move faster which causes water to expand and thus reduce the density of water.Below 4 degrees Celsius the effect of breaking of hydrogen bonds overcomes the increased speed of the smaller structural units and molecules and thus the density of water increases till 4 degrees celcius.But after this temperature the speed of units and molecules overcome the effect of breaking hydrogen bonds and thus density of water is decreased.Hence, water has a maximum density at 4 degrees Celsius.