Density= Mass/volume Volume of the 1 cup of water is 240 mL, Volume of 2.5 cup of water would be: 240 * 2.5 mL = 600 mL.= 600 cm^3 (Because mL and cm^3 are same units.) We know that density of water is 1g/cm3 and Density = Mass/volume, so putting the values of density and volume of 2.5 cups we would get, 1= Mass of 2.5 cups of water/600mL 1 g/cm^3= Mass/600 cm^3 600 g= Mass. So the mass of the 2.5 cups of water is 600 grams.