AFOQT Practice Test

What is a compound?

1. A mixture of different elements that cannot be separated

2. A substance made of two or more separate elements

3. A collection of mixtures

4. A pure substance made of one type of atom

The correct answer is: A substance made of two or more separate elements

A compound is defined as a substance formed when two or more different chemical elements are chemically bonded together. This bonding can result in properties that are distinct from those of the individual elements themselves. Compounds typically have a fixed ratio of the constituent elements, and they can be represented by a chemical formula, such as \(H_2O\) for water, which indicates that each molecule of water is comprised of two hydrogen atoms and one oxygen atom. The key feature that distinguishes a compound is the specific combination of different elements through chemical bonds, which is what makes option B the correct choice. In contrast, the other choices do not accurately describe a compound. For example, a mixture refers to a physical combination of substances that can be separated by physical means, which does not apply to compounds. A collection of mixtures implies a grouping without any chemical connection, and a pure substance made of one type of atom refers to an element, not a compound. Thus, the essence of what a compound is revolves around the chemical union of varied elements, solidifying option B as the accurate definition.