National League for Nursing (NLN) Science Practice Exam

A certain substance that is not broken down in a chemical reaction is most likely?

1. a compound.

2. an aqueous solution.

3. an element.

4. a heterogeneous mixture.

The correct answer is: an element.

The substance described in the question is most likely an element because elements are pure substances that cannot be broken down into simpler substances through chemical reactions. Each element consists of only one type of atom, making it fundamental to the structure of matter. Unlike compounds, which are made up of two or more different types of atoms and can be separated into those atoms through chemical means, elements remain intact in these reactions. Aqueous solutions refer to a mixture of substances where one or more solutes are dissolved in water, which can involve both elements and compounds. Heterogeneous mixtures, on the other hand, consist of multiple components that can be physically separated, and these components can be broken down or altered through chemical changes. Thus, referring to the characteristics of the descriptors, an element stands out as it retains its identity during chemical reactions.