Chemists often use molarity m, in moles/liter, to measure the concentration of solutions. molarity is a common unit of concentration because the volume of a liquid is very easy to measure. however, the drawback of using molarity is that volume is a temperature-dependent quantity. as temperature changes, density changes, which affects volume. volume markings for most laboratory glassware are calibrated for room temperature, about 20∘c. fortunately, there are several other ways of expressing concentration that do not involve volume and are therefore temperature independent. a 2.800×10−2 m solution of nacl in water is at 20.0∘c. the sample was created by dissolving a sample of nacl in water and then bringing the volume up to 1.000 l. it was determined that the volume of water needed to do this was 999.2 ml . the density of water at 20.0∘c is 0.9982 g/ml.