Question

What happens to the density of the layers as you move from the crust to the inner core? Which layer is the densest?

Answer 1

The layers will be denser as you move from the crust to the inner core.

The density are as the following:

crust (2.55 g/cm³)
upper mantle (3.9 g/cm³)
lower mantle (5 g/cm³)
outer core (11.05 g/cm³)
inner core (12.95 g/cm³)

Thus we can also see that the inner core is the densest layer.

Hope it helps!