What occurs when atoms are rearranged to form new substances?

When atoms are rearranged to form new substances, a chemical reaction occurs. During a chemical reaction, the bonds between atoms are broken and new bonds are formed, resulting in different substances with distinct properties compared to the reactants. This process involves the transformation of reactants into products through the rearrangement of their atomic structure.

In contrast, a physical change only alters the form or appearance of a substance without changing its chemical composition, such as melting ice into water or dissolving sugar in water. An isotopic change refers to the alteration of isotopes of an element, which does not necessarily involve the creation of new substances. Meanwhile, a nuclear reaction involves changes to the nucleus of an atom itself and typically results in the transformation of one element into another, rather than simply rearranging atoms to form new compounds. Therefore, choosing the option that identifies the formation of new substances through atom rearrangement accurately describes a chemical reaction.