Question

a gravel can be broken down into different kinds of substances by physical processes. no chemical reactions are needed to separate different parts of gravel into pure substances. this is because gravel is a(n)
compound
element
homogeneous mixture
heterogeneous mixture

Explanation:

Elements and compounds require chemical reactions to break - down into simpler substances. Homogeneous mixtures have uniform composition and are difficult to separate by simple physical means. Since gravel can be separated into different substances by physical processes and has a non - uniform composition, it is a heterogeneous mixture.

Answer:

D. heterogeneous mixture