Question

1. when chemicals combine to cause a new substance to form this is called a: atomic change molecular change physical change chemical change

Explanation:

A chemical change occurs when substances combine to form a new substance. In a physical change, the substance's form may change but its chemical identity remains the same. Atomic and molecular changes are more specific - atomic changes involve changes at the atomic level (like in nuclear reactions), and molecular changes can refer to changes in the arrangement of molecules which may or may not be a chemical change. Since the question is about chemicals combining to form a new substance, it is a chemical change.

Answer:

D. chemical change