Praxis Middle School Science (5442) Practice Test

The main idea is how matter is classified by whether it can be broken down into simpler parts by chemical means. An element is the kind of substance that cannot be decomposed into simpler substances by chemical reactions. In the options provided, the broad term that best fits this idea is substance, because it refers to a pure form of matter with a fixed composition (an element is one kind of substance). The other terms describe things that are not single, non-decomposable kinds of matter: molecules are groups of atoms that can often be broken into atoms, mixtures are combinations of substances that can be separated, and solutions are homogeneous mixtures. So the closest correct choice is substance.