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:

1. Recall the definitions:

• A compound is a pure substance made of two or more elements chemically bonded, and requires chemical reactions to break down.
• An element is a pure substance that cannot be broken down into simpler substances by chemical or physical means.
• A homogeneous mixture has a uniform composition throughout (e.g., salt water).
• A heterogeneous mixture has a non - uniform composition, and its components can be separated by physical processes.

1. Analyze gravel: Gravel has different substances (like different sized rocks, maybe sand particles etc.) that are not uniformly distributed, and can be separated by physical processes (like sieving). It is not a pure substance (so not compound or element), and it is not homogeneous (since composition is not uniform). So gravel is a heterogeneous mixture.

Answer:

D. heterogeneous mixture