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)\
\bigcirc compound\
\bigcirc element\
\bigcirc homogeneous mixture\
\bigcirc heterogeneous mixture

Explanation:

1. Recall the definitions:

• An element is a pure substance that cannot be broken down into simpler substances by chemical or physical means. But gravel can be broken into different substances, so it's not an element.
• A compound is a pure substance made of two or more elements chemically combined, and breaking it down requires chemical reactions (like decomposition). The problem states no chemical reactions are needed, so it's not a compound.
• A homogeneous mixture has a uniform composition throughout (e.g., salt water), while a heterogeneous mixture has a non - uniform composition with visible different components.
• Gravel has different parts (like different sized rocks, maybe different minerals) that can be separated by physical processes (like sieving) and has a non - uniform composition. So it's a heterogeneous mixture.

Answer:

D. heterogeneous mixture