Science, Tech, Math › Science Ideal Gas Definition Share Flipboard Email Print At low temperature, real gases behave like ideal gases. Greenhorn1/wikimedia commons/public domain 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 July 03, 2019 An ideal gas is a gas whose pressure P, volume V, and temperature T are related by the ideal gas law: PV = nRT where n is the number of moles of the gas and R is the ideal gas constant. Ideal gases are defined as having molecules of negligible size with an average molar kinetic energy dependent only on temperature. At a low temperature, most gases behave enough like ideal gases that the ideal gas law can be applied to them. An ideal gas is also known as a perfect gas.