Why Did The Earth Become Partially Molten?

As Earth heated, it became partially molten. Thirty to sixty percent of the Earth formed an outer magma ocean that was hundreds of kilometers thick. The interior of the Earth become soft. The heaviest elements sank to the middle and the lightest elements floated on top. This caused the formation of distinct layers in the Earth or, in other words, differentiate. These distinct layers consist of the core, mantle and crust. The inner core is solid iron and nickel because there is too much pressure for it to be liquid and is 1255 km thick. The density of the inner core is 12.6-13.5g/cm2 and the temperature is 4300-7000 degrees Celsius. Rotating around the inner core, the outer core is liquid iron and nickel and is 2220 km thick. The density of