# Density

densemass densitydensitiesdenserfluid densitydensestmatter densityaverage densityOrders of magnitude (density)Specific mass
The density (more precisely, the volumetric mass density; also known as specific mass), of a substance is its mass per unit volume.wikipedia
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### Osmium

Osos'''miumosmiophilic
Osmium and iridium are the densest known elements at standard conditions for temperature and pressure but certain chemical compounds may be denser.
Osmium is the densest naturally occurring element, with an experimentally measured (using x-ray crystallography) density of 22.59 g/cm3.

### Specific gravity

specific gravitiessgdensities
To simplify comparisons of density across different systems of units, it is sometimes replaced by the dimensionless quantity "relative density" or "specific gravity", i.e. the ratio of the density of the material to that of a standard material, usually water.
Specific gravity, also called relative density, is the ratio of the density of a substance to the density of a reference substance; equivalently, it is the ratio of the mass of a substance to the mass of a reference substance for the same given volume.

### Relative density

specific gravityspecific densityspecific gravities
To simplify comparisons of density across different systems of units, it is sometimes replaced by the dimensionless quantity "relative density" or "specific gravity", i.e. the ratio of the density of the material to that of a standard material, usually water.
Relative density, or specific gravity, is the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material.

### Mass concentration (chemistry)

mass concentrationw/vmass/volume
For a pure substance the density has the same numerical value as its mass concentration.
For a pure chemical the mass concentration equals its density (mass divided by volume); thus the mass concentration of a component in a mixture can be called the density of a component in a mixture.

### Buoyancy

buoyantbuoyant forcefloat
Different materials usually have different densities, and density may be relevant to buoyancy, purity and packaging.
For this reason, an object whose average density is greater than that of the fluid in which it is submerged tends to sink.

### Iridium

IrIr-192Ir(III)
Osmium and iridium are the densest known elements at standard conditions for temperature and pressure but certain chemical compounds may be denser.
The measured density of iridium is only slightly lower (by about 0.12%) than that of osmium, the densest metal known.

### Intensive and extensive properties

intensive propertyextensiveextensive property
Density is an intensive property in that increasing the amount of a substance does not increase its density; rather it increases its mass.
The same applies to the density of a homogeneous system; if the system is divided in half, the mass and the volume are both divided in half and the density remains unchanged.

### Specific weight

unit weightSpecific weight or Unit Weightweight density
In some cases (for instance, in the United States oil and gas industry), density is loosely defined as its weight per unit volume, although this is scientifically inaccurate – this quantity is more specifically called specific weight.

### Specific volume

The reciprocal of the density of a substance is occasionally called its specific volume, a term sometimes used in thermodynamics.
In thermodynamics, the specific volume of a substance is the ratio of the substance's volume to its mass. It is the reciprocal of density and an intrinsic property of matter as well.

### Archimedes

Archimedes of SyracuseArchimedeanArchimedes Heat Ray
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.
Archimedes had to solve the problem without damaging the crown, so he could not melt it down into a regularly shaped body in order to calculate its density.

### Hydrostatic weighing

hydrodensitometryBerman balance
Similarly, hydrostatic weighing uses the displacement of water due to a submerged object to determine the density of the object.
Hydrostatic weighing, also referred to as "underwater weighing", "hydrostatic body composition analysis", and "hydrodensitometry" is a technique for measuring the mass per unit volume of a living person's body.

### Temperature

temperaturesair temperaturewarm
In general, density can be changed by changing either the pressure or the temperature.

### Dasymeter

To determine the density of a liquid or a gas, a hydrometer, a dasymeter or a Coriolis flow meter may be used, respectively.
A dasymeter which allows weighing acts as a densimeter used to measure the density of gases.

### Volume

volumetriccapacityOrders of magnitude (volume)
In some cases (for instance, in the United States oil and gas industry), density is loosely defined as its weight per unit volume, although this is scientifically inaccurate – this quantity is more specifically called specific weight. The density (more precisely, the volumetric mass density; also known as specific mass), of a substance is its mass per unit volume.
The density of an object is defined as the ratio of the mass to the volume.

### Thermal expansion

coefficient of thermal expansionthermal expansion coefficientexpansion
The compressibility for a typical liquid or solid is 10 −6 bar −1 (1 bar = 0.1 MPa) and a typical thermal expansivity is 10 −5 K −1.
For example, the coefficient of thermal expansion of water drops to zero as it is cooled to 3.983 °C and then becomes negative below this temperature; this means that water has a maximum density at this temperature, and this leads to bodies of water maintaining this temperature at their lower depths during extended periods of sub-zero weather.

### Aerographite

With a density of 180 g/m 3 it is one of the lightest structural materials ever created.

### Water

H 2 OHOliquid water
For example, the density of water increases between its melting point at 0 °C and 4 °C; similar behavior is observed in silicon at low temperatures.
Water also differs from most liquids in that it becomes less dense as it freezes.

### Aerogel

aerogelssilica aerogelcarbon aerogel
The result is a solid with extremely low density and extremely low thermal conductivity.

### Dimensionless quantity

dimensionlessdimensionless numberdimensionless quantities
To simplify comparisons of density across different systems of units, it is sometimes replaced by the dimensionless quantity "relative density" or "specific gravity", i.e. the ratio of the density of the material to that of a standard material, usually water.
The power, P, in dimensions [M · L 2 /T 3 ], is a function of the density, ρ [M/L 3 ], and the viscosity of the fluid to be stirred, μ [M/(L · T)], as well as the size of the stirrer given by its diameter, D [L], and the angular speed of the stirrer, n [1/T].

### Metallic microlattice

metallic tube latticeMicrolatticemicrolattice of metallic tubes
With a density as low as 0.9 mg/cm 3 (0.00561 lb/ft 3 ), it is one of the lightest structural materials known to science.

### International System of Units

SISI unitsSI unit
The SI unit of kilogram per cubic metre (kg/m 3 ) and the cgs unit of gram per cubic centimetre (g/cm 3 ) are probably the most commonly used units for density.

### Alloy

alloysmetal alloyalloying
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.
The physical properties, such as density, reactivity, Young's modulus of an alloy may not differ greatly from those of its base element, but engineering properties such as tensile strength, ductility, and shear strength may be substantially different from those of the constituent materials.

### Mass flow meter

Coriolis meterMass flow meterscoriolis
To determine the density of a liquid or a gas, a hydrometer, a dasymeter or a Coriolis flow meter may be used, respectively.
Volumetric flow rate is the mass flow rate divided by the fluid density.

### Displacement (fluid)

displacementdisplaceddisplaces
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.
Thus buoyancy is expressed through Archimedes' principle, which states that the weight of the object is reduced by its volume multiplied by the density of the fluid.

### Eureka (word)

EurekaEureka!Heureka
As a result, the term "eureka" entered common parlance and is used today to indicate a moment of enlightenment.
Equipment for weighing objects with a fair amount of precision already existed, and now that Archimedes could also measure volume, their ratio would give the object's density, an important indicator of purity (as gold is nearly twice as dense as silver and has significantly greater weight for the same volume of matter at standard temperatures and pressure).