The density of a substance is defined as the amount (mass) of the substance per unit volume. It is often denoted using the Latin letter D or ρ; the lower case Greek letter pronounced rho. The formula of density is given by ρ = m/v, where m is for the mass of the substance and v is for its volume present. From the equation, it is clear that density is directly proportional to mass and indirectly proportional to volume.
Factors that affect the density values of a substance are pressure and temperature. Increasing the pressure and decreasing the temperature will bring up the density value of a substance as the volume is reduced by these changes. Similarly, by increasing the temperature and decreasing the pressure, the density value can be brought down as the volume value goes up. The effect of temperature and pressure on the density of a substance can be significantly noticeable in gasses when compared with solids or liquids. Generally, the densest materials are solids, followed by liquids and then gasses, in that specific order. This is because solids, by nature, have much firmly packed, tight molecules, and on the other end, gases have much more loose, freely packed molecules, and liquids lie in the middle in terms of how closely the molecules in it are packed.
In the case of a pure substance that does not contain any impurities, the value of density is equal to the mass concentration of that substance. Different materials typically have their very own value of density, depending on that material’s buoyancy, purity and packaging. In some cases, the reciprocal of the density of a substance is called the specific volume of that substance. The specific volume of a substance is defined as the total volume occupied by a certain mass of that substance. The specific volume of a substance is an intrinsic property, while the density of the substance is an intensive property.
Since the formula for the density of a substance is the mass of that substance divided by the volume of that substance, density can technically be expressed in terms of any unit of mass divided by any unit of volume. However, for standardization, the SI unit of density, kilogram per cubic meter (kg/ m 3 ), is the most widely used unit. In addition, the cgs (centimeter gram second system of units) unit of gram per cubic centimeter (g/cm 3 ) is also used prominently. But since the measured density of a sample of any substance can range from very small values to significantly high values, it is more practical to use an appropriate unit of mass and volume to arrive at the best unit of density specific to that industry. Some other units of density are listed below.
The knowledge of the density of different substances is very handy and serves a great deal of purpose in various fields. Some are discussed below.