Chapter 25, Problem 3RAT

Why are silicon and oxygen concentrated near Earth’s surface while iron is concentrated at the core?

(a) Earth’s materials separated early in its history through the process of density segregation.

(b) Silicon and oxygen are less dense than iron.

(c) Both of these.

(d) Neither of these.

To determine

The correct option for the statement “Why are silicon and oxygen concentrated near Earth’s surface while iron is concentrated at the core?”

Answer to Problem 3RAT

The correct option for the statement “Why are silicon and oxygen concentrated near Earth’s surface while iron is concentrated at the core?” is option (c).

Explanation of Solution

It is due to density segregation that the outermost layer is least dense, which is known as the crust, then is the second layer called mantle and lastly, the inner densest layer is metallic core.

In the formation of Earth, the elements were evenly distributed over the planet. But after every meteorite effect heat was produced. Due to Earth’s gravity, it attached more elements which led to the pressing of Earth to a smaller volume. This process also generated heat. The decay of a radioactive element also produces heat. All these processes took Earth to its melting point.

Now, in a molten state and due to gravity, the denser material was deposited at the centre of Earth and less-dense on the surface. Since, silicon and oxygen are less dense than iron, so they are concentrated near Earth’s surface while the iron is concentrated at the core.

Conclusion:

Therefore, the correct option for the statement “Why are silicon and oxygen concentrated near Earth’s surface while iron is concentrated at the core?” is option (c).