The volume change upon mixing is often called the "volume excess" which in this case is a negative value. Report the volume excess for a 50-50 (by volume) mixture in an intensive fashion as the molar quantity below where n is the total number of entities of both components and AV is the deviation from the expected volume of the mixture. You can use the following densities: water (0.997 g/mL), ethanol (0.789 g/mL), isopropanol (0.786 g/mL). molar volume excess= AV / n