Physical properties are characteristics that scientists can measure without changing the composition of the sample under study, such as mass, color, and volume. Physical properties can be extensive or intensive. Extensive properties vary with the amount of the substance and include mass, weight, and volume.
Mass and volume are both extensive properties, their ratio is an important intensive property called density ( ρ ). Density is defined as mass per unit volume and is usually expressed in grams per cubic centimeter (g/cm³). As mass increases in a given volume, density also increases. At a given temperature and pressure, the density of a pure substance is a constant:
