Science, Tech, Math › Science Boiling Point Elevation What Boiling Point Elevation Is and How It Works Share Flipboard Email Print Adding salt to water increases its boiling point, but you'd have to add a lot of salt to make a difference when cooking. Liam Norris / 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 May 07, 2019 Boiling point elevation occurs when the boiling point of a solution becomes higher than the boiling point of a pure solvent. The temperature at which the solvent boils is increased by adding any non-volatile solute. A common example of boiling point elevation can be observed by adding salt to water. The boiling point of the water is increased (although in this case, not enough to affect the cooking rate of food). Boiling point elevation, like freezing point depression, is a colligative property of matter. This means it depends on the number of particles present in a solution and not on the type of particles or their mass. In other words, increasing the concentration of the particles increases the temperature at which the solution boils. How Boiling Point Elevation Works In a nutshell, boiling point increases because most of the solute particles remain in the liquid phase rather than enter the gas phase. In order for a liquid to boil, its vapor pressure needs to exceed ambient pressure, which is harder to achieve once you add a nonvolatile component. If you like, you could think of adding a solute as diluting the solvent. It doesn't matter whether the solute is an electrolyte or not. For example, boiling point elevation of water occurs whether you add salt (an electrolyte) or sugar (not an electrolyte). Boiling Point Elevation Equation The amount of boiling point elevation can be calculated using the Clausius-Clapeyron equation and Raoult's law. For an ideal dilute solution: Boiling Pointtotal = Boiling Pointsolvent + ΔTb where ΔTb = molality * Kb * i with Kb = ebullioscopic constant (0.52°C kg/mol for water) and i = Van't Hoff factor The equation is also commonly written as: ΔT = Kbm The boiling point elevation constant depends on the solvent. For example, here are constants for some common solvents: Solvent Normal Boiling Point, oC Kb, oC m-1 water 100.0 0.512 benzene 80.1 2.53 chloroform 61.3 3.63 acetic acid 118.1 3.07 nitrobenzene 210.9 5.24 A Sample Problem on How to Calculate Boiling Point Elevation Temperature The Simple Science of Why Salt Increases Water's Boiling Point What Boiling Point Elevation Means What Are Colligative Properties? When You Should Use Molality Rather Than Molarity Everything You Need to Know About Saturated Solutions in Chemistry Understand What Solubility Means in Chemistry Does Adding Salt Lower the Boiling Point of Water? What Is a Strong Electrolyte? Use Science to Make Ice Cream in a Bag (No Freezer Required) Do You Know How to Use Ionic Equations in Chemistry? What Is the Common-Ion Effect? What Is Freezing Point Depression and How Does It Work? What Is an Aqueous Solution? Chemistry Definition and Example What It Means When Something Crystallizes At What Temperature Does Water Boil?