Final answer:
Gravity on Earth would be weaker if the core was silicate instead of iron, because the overall mass of the planet would be less due to the lower density of silicates compared to iron and nickel.
Step-by-step explanation:
If Earth's core were silicate and not iron, gravity would be weaker than it is now. This is because silicates are less dense than iron and since gravity is influenced by mass, a silicate core would have less mass and therefore exercise a weaker gravitational pull on objects at Earth's surface. The current core, made predominantly iron and nickel is extremely dense, contributing to Earth's strong gravity.
Furthermore one of the reasons Earth has a metallic core is because of planetary differentiation, which caused heavier metals, like iron to sink towards the center during Earth's molten phase while lighter silicates rose towards the surface.