Density is a physical property of matter. Density of a substance can be determined by measuring and . These measurement are used in the formula to determine the density of the substance. Density values are useful when trying to an unknown substance. Units used for density are g/mL and g/cm 3 . Units of are used for the density of liquids. Units of are used for the density of solids. Density describes how much matter is found in a specific volume of a substance. So g/mL really means measured in grams per measured in milliliters and g/cm 3 really means measured in grams per measured in cubic centimeters. Water has a density of 1.0 g/mL. Substances like most woods have density values that are water and so they float when placed in water. Substances like potato cubes have density values that are water and so they sink when placed in water.