Science, Tech, Math › Science Amphoteric: Definition and Examples in Chemistry Amphoteric substances can act as either an acid or a base Share Flipboard Email Print Self-ionizing compounds, such as water, are examples of amphoteric molecules which are also amphiprotic. Yuji Sakai/Getty Images Science Chemistry Chemical Laws Basics 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 September 22, 2019 An amphoteric substance is one that can act as either an acid or a base, depending on the medium. The word comes from the Greek amphoteros or amphoteroi, meaning "each or both of two" and, essentially, "either acid or alkaline." Amphiprotic molecules are a type of amphoteric species that either donates or accepts a proton (H+), depending on the conditions. Not all amphoteric molecules are amphiprotic. For example, ZnO acts as a Lewis acid, which can accept an electron pair from OH but cannot donate a proton. Ampholytes are amphoteric molecules that exist primarily as zwitterions over a given pH range and have both acidic groups and basic groups. Here are some examples of amphoterism: Metal oxides or hydroxides are amphoteric. Whether a metal compound acts as an acid or a base depends on the oxide oxidation state.Sulfuric acid (H2SO4) is an acid in water but is amphoteric in superacids.Amphiprotic molecules, such as amino acids and proteins, are amphoteric.