A ___ is shaped like a ball, with all points on the surface at an equal distance from the center.

Is Earth a perfect sphere?

Which are systems of Earth?

Which system of Earth is made up of Earth's entire body?

What is the force that every object exerts on all other objects because of their masses?

Mass and ___ affect the strength of the gravitational force between objects.

As the thermal energy melted some of Earth's material, it began to flow and form distinct ____ of different materials.

The different materials formed layers according to their ___.

When Earth started melting, the densest materials sank and formed the ___ layers.

The least dense materials stayed at the ___ and formed a separate layer.

The materials with the ___(in the middle) densities formed layers in between the top layer and the bottom layer.

Which is the densest layer?