Science, Tech, Math › Science Phase Definition and Examples Share Flipboard Email Print Plasma is a phase of matter. Roland Bordas / EyeEm / 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 13, 2019 In chemistry and physics, a phase is a physically distinctive form of matter, such as a solid, liquid, gas, or plasma. A phase of matter is characterized by having relatively uniform chemical and physical properties. Phases are different from states of matter. The states of matter (e.g., liquid, solid, gas) are phases, but matter can exist in different phases yet remain in the same state of matter. For example, liquid mixtures can exist in multiple phases, such as an oil phase and an aqueous phase. The term phase may also be used to describe equilibrium states on a phase diagram. When phase is used in this context, it's typically synonymous with a state of matter because the qualities that describe the phase include the organization of matter as well as variables such as temperature and pressure. Phases of Matter The distinct phases used to describe states of matter include: Solid: Closely packed particles with a fixed volume and shapeLiquid: Fluid particles with a fixed volume but variable shapeGas: Fluid particles with neither a fixed volume nor shapePlasma: Charged particles with no fixed volume or shapeBose-Einstein condensate: A diluted, cold boson gasMesophases: Intermediate phases between solid and liquid There may be multiple phases within a single state of matter. For example, a bar of solid iron may contain multiple phases (e.g., martensite, austenite.) An oil and water mixture is a liquid that will separate into two phases. Interface At equilibrium, there is a narrow space between two phases where the matter doesn't exhibit properties of either phase. This region, known as interface, may be very thin, yet can exert significant effects.