Science, Tech, Math › Science Phase Change Definition Share Flipboard Email Print The boiling point of water is is the phase change from the liquid to vapor state. Jody Dole / 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 February 04, 2019 Definition: A phase change is a change in the state of matter of a sample. A phase change is an example of a physical change. Also Known As: phase transition Examples: An example of a phase change is water changing from a liquid to vapor. Another example of a phase change is melted wax cooling into solid wax.