Suppose you mix several liquids in a jar. after a few minutes, the liquids form layers. is this a homogenous mixture or a heterogenous mixture? why?

heterogeneous mixture, because, the layers are called phases and a heterogeneous mixture has two or more phases. the oil phase is less dense then water so it floats on top, etc.

the mantle

explanation:

earth is divided into three layers: the crust or the outermost layer on which we live; the underlying, middle layer - the mantle - and the core (the innermost layer of earth).