Science, Tech, Math › Science What Is a Pure Substance? Scientific Definition of Purity Share Flipboard Email Print Honey is an example of a pure substance. skaman306 / Getty Images Science Chemistry Basics Chemical Laws Molecules Periodic Table Projects & Experiments Scientific Method Biochemistry Physical Chemistry Medical Chemistry Chemistry In Everyday Life Famous Chemists Activities for Kids Abbreviations & Acronyms Biology Physics Geology Astronomy Weather & Climate By Anne Marie Helmenstine, Ph.D. Chemistry Expert Ph.D., Biomedical Sciences, University of Tennessee at Knoxville B.A., Physics and Mathematics, Hastings College Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels. our editorial process Facebook Facebook Twitter Twitter Anne Marie Helmenstine, Ph.D. Updated January 06, 2020 You may have wondered what is meant by the term "pure substance." Here's a look at what a pure substance is and how you can tell if a substance is pure or not. Any Material Free of Contamination In a nutshell, a pure substance is any single type of material. A substance can be anything. It doesn't have to consist of a single element or type of molecule. Pure hydrogen is a pure substance. So is pure honey, even though it consists of many different types of molecules. What makes both of these materials pure substances is that they are free from contamination. If you add some oxygen to the hydrogen, the resulting gas is neither pure hydrogen nor pure oxygen. If you add corn syrup to the honey, you no longer have pure honey. Pure alcohol could be ethanol, methanol, or a mixture of different alcohols, but as soon as you add water (which is not alcohol), you no longer have a pure substance. "Building Block" of Matter Some people define a pure substance to be a material that consists of one type of "building block" of matter. By this definition, only elements and compounds are pure substances, while homogenous mixtures are not. Generally, it does not matter which definition you use, but if you are asked to give examples of pure substances as a homework assignment, use those that meet the narrow definition, such as gold, silver, water, and salt.