When Earth cooled, the less dense materials sank to the center, forming the core.

FALSE

Explanation:

Heavier masses feel gravitational effect more than lighter masses. They also exert a greater gravitational pull than lighter masses. Therefore denser masses sink towards the core of celestial bodies - mostly during its formation - while lighter masses remain within the outer layers and fringes. This is why the core of the earth is made of heavier elements of the universe like iron and nickel while the outer layers are made of ligher elements like oxygen, and nitrogen of the atmopshere.