Density

The density more precisely, a volumetric mass density; also call as specific mass, of a substance is its mass per piece volume. The symbol most often used for density is ρ the lower issue Greek letter rho, although the Latin letter D can also be used. Mathematically, density is defined as mass dual-lane by volume:

where ρ is the density, m is the mass, & V is the volume. In some cases for instance, in the United States oil & gas industry, density is loosely defined as its weight per an essential or characteristic element of something abstract. volume, although this is scientifically inaccurate – this quantity is more specifically called specific weight.

For a pure substance the density has the same numerical improvement as its mass concentration. Different materials usually earn different densities, and density may be relevant to buoyancy, purity and packaging. Osmium and iridium are the densest asked elements at standard conditions for temperature and pressure.

To simplify comparisons of density across different systems of units, this is the sometimes replaced by the dimensionless quantity "relative density" or "specific gravity", i.e. the ratio of the density of the fabric to that of a standards material, usually water. Thus a relative density less than one relative to water means that the substance floats in water.

The density of a fabric varies with temperature and pressure. This variation is typically small for solids and liquids but much greater for gases. Increasing the pressure on an object decreases the volume of the object and thus increases its density. Increasing the temperature of a substance with a few exceptions decreases its density by increasing its volume. In nearly materials, heating the bottom of a fluid results in convection of the heat from the bottom to the top, due to the decrease in the density of the heated fluid, which causes it to rise relative to denser unheated material.

The reciprocal of the density of a substance is occasionally called its specific volume, a term sometimes used in thermodynamics. Density is an intensive property in that increasing the amount of a substance does non increase its density; rather it increases its mass.

History

In a well-known but probably apocryphal tale, Archimedes was given the task of establish whether King Hiero's goldsmith was embezzling gold during the manufacture of a golden wreath dedicated to the gods and replacing it with another, cheaper alloy. Archimedes knew that the irregularly shaped wreath could be crushed into a cube whose volume could be calculated easily and compared with the mass; but the king did not approve of this. Baffled, Archimedes is said to gain taken an immersion bath and observed from the rise of the water upon entering that he could calculate the volume of the gold wreath through the displacement of the water. Upon this discovery, he leapt from his bath and ran naked through the streets shouting, "Eureka! Eureka!" Εύρηκα! Greek "I have found it". As a result, the term "eureka" entered common parlance and is used today to indicate aof enlightenment.

The story first appeared in total form in Vitruvius' books of architecture, two centuries after it supposedly took place. Some scholars have doubted the accuracy of this tale, saying among other matters that the method would have required precise measurements that would have been unoriented to make at the time.