Food Science CDE Practice Exam 2026 - Free Food Science Practice Questions and Study Guide

A pure substance is defined as a material that is composed of only one type of particle, which means it has a consistent and uniform composition throughout. Table salt, which is chemically known as sodium chloride, is a prime example of a pure substance because it consists solely of sodium ions and chloride ions in a fixed ratio. This chemical structure results in properties that are uniform and predictable.

In contrast, the other options represent mixtures rather than pure substances. Dill pickles, for instance, contain various ingredients such as cucumbers, vinegar, spices, and seasonings, resulting in a heterogeneous mixture with varying compositions. Chocolate is also a mixture, comprising cocoa solids, sugar, fats, and sometimes milk, creating a variety of flavors and textures. Ketchup, too, consists of a mix of tomatoes, vinegar, spices, and sweeteners, making it another example of a complex mixture rather than a pure substance.