This article is about mass density. A graduated cylinder containing various density of various materials pdf liquids with different densities.
The density, or more precisely, the volumetric mass density, of a substance is its mass per unit volume. Latin letter D can also be used. For a pure substance the density has the same numerical value as its mass concentration.
Different materials usually have different densities, and density may be relevant to buoyancy, purity and packaging. Osmium and iridium are the densest known elements at standard conditions for temperature and pressure but certain chemical compounds may be denser.
To simplify comparisons of density across different systems of units, it is sometimes replaced by the dimensionless quantity “relative density” or “specific gravity”, i. Thus a relative density less than one means that the substance floats in water. The density of a material 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. In most 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. This causes it to rise relative to more dense unheated material.
The reciprocal of the density of a substance is occasionally called its specific volume, a term sometimes used in thermodynamics. In a well-known but probably apocryphal tale, Archimedes was given the task of determining 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.
Baffled, Archimedes is said to have 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!
As a result, the term “eureka” entered common parlance and is used today to indicate a moment of enlightenment. The story first appeared in written 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 things that the method would have required precise measurements that would have been difficult to make at the time. As there are many units of mass and volume covering many different magnitudes there are a large number of units for mass density in use. The cubic centimeter can be alternately called a millilitre or a cc.