View source for Density

{{about|mass density}}
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{{Use mdy dates|date=October 2015}}
{{Infobox physical quantity
| bgcolour    = {default}
| name        = Density
| image       =
| caption     =
| unit        = kg/m<sup>3</sup>
| symbols     = ''[[Rho|ρ]]'', ''D''
| dimension = wikidata
| derivations = <math> \rho = \frac{m}{V}</math>
}}[[File:Artsy density column.png|thumb|150px|A [[graduated cylinder]] containing various coloured liquids with different densities]]

The '''density''' (more precisely, the '''volumetric mass density'''; also known as '''specific mass'''), of a substance is its [[mass]] per unit [[volume]]. The symbol most often used for density is ''ρ'' (the lower case Greek letter [[Rho (letter)|rho]]), although the Latin letter ''D'' can also be used. Mathematically, density is defined as mass divided by volume:<ref>{{cite web | url =http://www.grc.nasa.gov/WWW/BGH/fluden.html | title =Gas Density Glenn research Center | author =''[[National Aeronautic and Space Administration|The National Aeronautic and Atmospheric Administration's]]'' ''[[Glenn Research Center]]'' | publisher =grc.nasa.gov | url-status =dead | archiveurl =https://web.archive.org/web/20130414132531/http://www.grc.nasa.gov/WWW/BGH/fluden.html | archivedate =April 14, 2013 | df =mdy-all | access-date =April 9, 2013 }}</ref> 

:<math> \rho = \frac{m}{V}</math>

where ''ρ'' is the density, ''m'' is the mass, and ''V'' is the volume. In some cases (for instance, in the United States oil and gas industry), density is loosely defined as its [[weight]] per unit [[volume]],<ref>{{cite web|url=http://oilgasglossary.com/density.html |title=Density definition in Oil Gas Glossary |publisher=Oilgasglossary.com |accessdate=September 14, 2010 |url-status=dead |archiveurl=https://web.archive.org/web/20100805010226/http://oilgasglossary.com/density.html |archivedate=August 5, 2010 }}</ref> although this is scientifically inaccurate – this quantity is more specifically called [[specific weight]].

For a pure substance the density has the same numerical value as its [[mass concentration (chemistry)|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{{Citation needed|date=September 2019}} 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.e. the ratio of the density of the material to that of a standard material, usually water. 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. Increasing the temperature of a substance (with a few exceptions) decreases its density by increasing its volume. 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]]. Density is an [[intensive property]] in that increasing the amount of a substance does not increase its density; rather it increases its mass.

== History ==

In a well-known but probably [[apocrypha|apocryphal]] tale, [[Archimedes]] was given the task of determining whether [[Hiero II of Syracuse|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]].<ref>[http://www-personal.umich.edu/~lpt/archimedes.htm Archimedes, A Gold Thief and Buoyancy] {{webarchive|url=https://web.archive.org/web/20070827113533/http://www-personal.umich.edu/~lpt/archimedes.htm |date=August 27, 2007 }} – by Larry "Harris" Taylor, Ph.D.</ref> 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 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 (fluid)|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 (word)|eureka]]" entered common parlance and is used today to indicate a moment of enlightenment.

The story first appeared in written form in [[Vitruvius]]' ''[[De architectura|books of architecture]]'', two centuries after it supposedly took place.<ref>[http://penelope.uchicago.edu/Thayer/E/Roman/Texts/Vitruvius/9*.html Vitruvius on Architecture, Book IX]{{Dead link|date=December 2018 |bot=InternetArchiveBot |fix-attempted=yes }}, paragraphs 9–12, translated into English and [http://penelope.uchicago.edu/Thayer/L/Roman/Texts/Vitruvius/9*.html in the original Latin].</ref> 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.<ref>{{cite journal|doi=10.1126/science.305.5688.1219e|title=EXHIBIT: The First Eureka Moment|year=2004|journal=Science|volume=305|issue=5688|pages=1219e }}</ref><ref>[http://www.sciam.com/article.cfm?articleID=5F1935E9-E7F2-99DF-3F1D1235AF1D2CD1 Fact or Fiction?: Archimedes Coined the Term "Eureka!" in the Bath], ''Scientific American'', December 2006.</ref>

From the equation for density (''ρ'' = ''m''/''V''), mass density has units of mass divided by volume. 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 [[SI]] unit of [[kilogram]] per [[cubic metre]] (kg/m<sup>3</sup>) and the [[cgs]] unit of [[gram]] per [[cubic centimetre]] (g/cm<sup>3</sup>) are probably the most commonly used units for density. One g/cm<sup>3</sup> is equal to one thousand kg/m<sup>3</sup>.  One cubic centimetre (abbreviation cc) is equal to one millilitre. In industry, other larger or smaller units of mass and or volume are often more practical and [[US customary units]] may be used. See below for a list of some of the most common units of density.

== Measurement of density ==
A number of techniques as well as standards exist for the measurement of density of materials. Such techniques include the use of a hydrometer (a buoyancy method for liquids), Hydrostatic balance (a buoyancy method for liquids and solids), immersed body method (a buoyancy method for liquids), pycnometer (liquids and solids), air comparison pycnometer (solids), oscillating densitometer (liquids), as well as pour and tap (solids).<ref>{{Cite web|url=https://www.oecd-ilibrary.org/environment/test-no-109-density-of-liquids-and-solids_9789264123298-en|title=OECD Test Guideline 109 on measurement of density|last=|first=|date=|website=|access-date=}}</ref> However, each individual method or technique measures different types of density (e.g. bulk density, skeletal density, etc.), and therefore it is necessary to have an understanding of the type of density  being measured as well as the type of material in question. 

===Homogeneous materials===
The density at all points of a [[Homogeneous (chemistry)|homogeneous]] object equals its total [[mass]] divided by its total volume. The mass is normally measured with a [[weighing scale|scale or balance]]; the volume may be measured directly (from the geometry of the object) or by the displacement of a fluid. To determine the density of a liquid or a gas, a [[hydrometer]], a [[dasymeter]] or a [[Coriolis flow meter]] may be used, respectively. Similarly, [[hydrostatic weighing]] uses the displacement of water due to a submerged object to determine the density of the object.

===Heterogeneous materials===
If the body is not homogeneous, then its density varies between different regions of the object. In that case the density around any given location is determined by calculating the density of a small volume around that location. In the limit of an infinitesimal volume the density of an inhomogeneous object at a point becomes: <math>\rho(\vec{r}) = dm/dV</math>, where <math>dV</math> is an elementary volume at position <math>r</math>. The mass of the body then can be expressed as

:<math>
 m = \int_V \rho(\vec{r})\,dV.
</math>

=== Non-compact materials ===
In practice, bulk materials such as sugar, sand, or snow contain voids. Many materials exist in nature as flakes, pellets, or granules.

Voids are regions which contain something other than the considered material.  Commonly the void is air, but it could also be vacuum,  liquid, solid, or a different gas or gaseous mixture.

The bulk volume of a material—inclusive of the void fraction—is often obtained by a simple measurement (e.g. with a calibrated measuring cup) or geometrically from known dimensions.

Mass divided by ''bulk'' volume determines [[bulk density]].  This is not the same thing as volumetric mass density.

To determine volumetric mass density, one must first discount the volume of the void fraction. Sometimes this can be determined by geometrical reasoning.  For the [[close-packing of equal spheres]] the non-void fraction can be at most about 74%.  It can also be determined empirically.  Some bulk materials, however, such as sand, have a ''variable'' void fraction which depends on how the material is agitated or poured. It might be loose or compact, with more or less air space depending on handling.

In practice, the void fraction is not necessarily air, or even gaseous.  In the case of sand, it could be water, which can be advantageous for measurement as the void fraction for sand saturated in water—once any air bubbles are thoroughly driven out—is potentially more consistent than dry sand measured with an air void.

In the case of non-compact materials, one must also take care in determining the mass of the material sample. If the material is under pressure (commonly ambient air pressure at the earth's surface) the determination of mass from a measured sample weight might need to account for buoyancy effects due to the density of the void constituent, depending on how the measurement was conducted. In the case of dry sand, sand is so much denser than air that the buoyancy effect is commonly neglected (less than one part in one thousand).

Mass change upon displacing one void material with another while maintaining constant volume can be used to estimate the void fraction, if the difference in density of the two voids materials is reliably known.

== Changes of density ==
{{Main article|Compressibility|Thermal expansivity}}

In general, density can be changed by changing either the [[pressure]] or the [[temperature]]. Increasing the pressure always increases the density of a material. Increasing the temperature generally decreases the density, but there are notable exceptions to this generalization. For example, the density of [[water]] increases between its melting point at 0&nbsp;°C and 4&nbsp;°C; similar behavior is observed in [[silicon]] at low temperatures.

The effect of pressure and temperature on the densities of liquids and solids is small. The [[compressibility]] for a typical liquid or solid is 10<sup>−6</sup>&nbsp;[[bar (unit)|bar]]<sup>−1</sup> (1&nbsp;bar = 0.1&nbsp;MPa) and a typical [[thermal expansivity]] is 10<sup>−5</sup>&nbsp;[[Kelvin|K]]<sup>−1</sup>. This roughly translates into needing around ten thousand times atmospheric pressure to reduce the volume of a substance by one percent. (Although the pressures needed may be around a thousand times smaller for sandy soil and some clays.) A one percent expansion of volume typically requires a temperature increase on the order of thousands of degrees [[Celsius]].

In contrast, the density of gases is strongly affected by pressure. The density of an [[ideal gas]] is
:<math>\rho = \frac {MP}{RT},</math>

where {{math|M}} is the [[molar mass]], {{math|P}} is the pressure, {{math|R}} is the [[Gas constant|universal gas constant]], and {{math|T}} is the [[absolute temperature]]. This means that the density of an ideal gas can be doubled by doubling the pressure, or by halving the absolute temperature.

In the case of volumic thermal expansion at constant pressure and small intervals of temperature the temperature dependence of density is :
:<math>\rho = \frac{\rho_{T_0}}{1 + \alpha \cdot \Delta T}</math>

where <math>\rho_{T_0}</math> is the density at a reference temperature, <math>\alpha</math> is the thermal expansion coefficient of the material at temperatures close to <math>T_0</math>.

== Density of solutions ==
The density of a [[solution]] is the sum of [[mass concentration (chemistry)|mass (massic) concentrations]] of the components of that solution.

Mass (massic) concentration of each given component ρ<sub>i</sub> in a solution sums to density of the solution.
:<math>\rho = \sum_i \varrho_i \,</math>

Expressed as a function of the densities of pure components of the mixture and their [[volume concentration|volume participation]], it allows the determination of [[excess molar quantity|excess molar volumes]]:
:<math>\rho = \sum_i \rho_i \frac{V_i}{V}\, = \sum_i \rho_i \varphi_i = \sum_i \rho_i \frac{V_i}{\sum_i V_i + \sum_i {V^E}_i}</math>
provided that there is no interaction between the components.

Knowing the relation between excess volumes and activity coefficients of the  components, one can determine the activity coefficients.
:<math>\overline{V^E}_i = RT \frac{\partial\ln\gamma_i}{\partial P}</math>

== Densities ==

=== Various materials ===
:''Selected chemical elements are listed here. For the densities of all chemical elements, see [[List of chemical elements]]''

{| class="wikitable sortable" style="text-align:center;"
|+Densities of various materials covering a range of values
|-
! Material
! ''ρ'' (kg/m<sup>3</sup>)<ref group=note>Unless otherwise noted, all densities given are at [[standard conditions for temperature and pressure]],<br>that is, {{convert|273.15|K|C|abbr=on|lk=in}} and {{convert|100|kPa|atm|3|abbr=on}}.</ref>
! class="unsortable" | Notes
|-0.08988
| [[Hydrogen]]                 || 0.0898 ||
|-
| [[Helium]]                   || 0.179  ||
|-
| [[Aerographite]]             || 0.2    || <ref group=note name=noair>Air contained in material excluded when calculating density</ref><ref>[http://phys.org/news/2012-07-carbon-nanotube-struructure-aerographite-lightest.html New carbon nanotube struructure aerographite is lightest material champ] {{webarchive|url=https://web.archive.org/web/20131017064205/http://phys.org/news/2012-07-carbon-nanotube-struructure-aerographite-lightest.html |date=October 17, 2013 }}. Phys.org (July 13, 2012). Retrieved on July 14, 2012.</ref><ref>[http://www.spiegel.de/wissenschaft/technik/aerographit-leichtestes-material-der-welt-entwickelt-a-843819.html Aerographit: Leichtestes Material der Welt entwickelt – SPIEGEL ONLINE] {{webarchive|url=https://web.archive.org/web/20131017083053/http://www.spiegel.de/wissenschaft/technik/aerographit-leichtestes-material-der-welt-entwickelt-a-843819.html |date=October 17, 2013 }}. Spiegel.de (July 11, 2012). Retrieved on July 14, 2012.</ref>
|-
| [[Metallic microlattice]]    || 0.9    || <ref group=note name=noair/>
|-
| [[Aerogel]]                  || 1.0    || <ref group=note name=noair/>
|-
| [[Air]]                      || 1.2    || At sea level
|-
| [[Tungsten hexafluoride]]    || 12.4   || One of the heaviest known gases at standard conditions
|-
| [[Liquid hydrogen]]          || 70     || At approx. −255&nbsp;°C
|-
| [[Expanded polystyrene|Styrofoam]]                || 75     || Approx.<ref name="madsci1">{{cite web |url=http://www.madsci.org/posts/archives/mar2000/954534602.Ph.r.html |title=Re: which is more {{sic|bou|yant|nolink=y}} styrofoam or cork |publisher=Madsci.org |accessdate=September 14, 2010 |url-status=live |archiveurl=https://web.archive.org/web/20110214145901/http://www.madsci.org/posts/archives/mar2000/954534602.Ph.r.html |archivedate=February 14, 2011 |df=mdy-all }}</ref>
|-
| [[Cork (material)|Cork]]     || 240    || Approx.<ref name="madsci1" />
|-
| [[Pine]]                     || 373    || <ref name="SerwayJewett2005">{{citation|author1=Raymond Serway|author2=John Jewett|title=Principles of Physics: A Calculus-Based Text|url=https://books.google.com/books?id=VaroJ5BNuZAC|year=2005|publisher=Cengage Learning|isbn=0-534-49143-X|page=467|url-status=live|archiveurl=https://web.archive.org/web/20160517053840/https://books.google.com/books?id=VaroJ5BNuZAC|archivedate=May 17, 2016|df=mdy-all}}</ref>
|-
| [[Lithium]]                  || 535    ||
|-
| [[Wood]]                     || 700    || Seasoned, typical<ref name=wood0>{{cite web |url=http://www.engineeringtoolbox.com/wood-density-d_40.html |title=Wood Densities |accessdate=October 15, 2012 |work=www.engineeringtoolbox.com |url-status=live |archiveurl=https://web.archive.org/web/20121020065545/http://www.engineeringtoolbox.com/wood-density-d_40.html |archivedate=October 20, 2012 |df=mdy-all }}</ref><ref name=wood1>{{cite web |title=Density of Wood |url=http://www.simetric.co.uk/si_wood.htm |accessdate=October 15, 2012 |work=www.simetric.co.uk |url-status=live |archiveurl=https://web.archive.org/web/20121026115734/http://www.simetric.co.uk/si_wood.htm |archivedate=October 26, 2012 |df=mdy-all }}</ref>
|-
| [[Oak]]                      || 710    || <ref name="SerwayJewett2005">{{citation|author1=Raymond Serway|author2=John Jewett|title=Principles of Physics: A Calculus-Based Text|url=https://books.google.com/books?id=VaroJ5BNuZAC|year=2005|publisher=Cengage Learning|isbn=0-534-49143-X|page=467|url-status=live|archiveurl=https://web.archive.org/web/20160517053840/https://books.google.com/books?id=VaroJ5BNuZAC|archivedate=May 17, 2016|df=mdy-all}}</ref>
|-
| [[Potassium]]                || 860    || <ref name="crc2ed">CRC Press Handbook of tables for Applied Engineering Science, 2nd Edition, 1976, Table 1-59</ref> 
|-
| [[Ice]]                      || 916.7  || At temperature <&nbsp;0&nbsp;°C<!-- Sourced from the "Ice" page -->
|-
| [[Cooking oil]]              || 910–930 ||
|-
| [[Sodium]]                   || 970    ||
|-
| [[Water]] (fresh)            || 1,000  || At 4&nbsp;°C, the temperature of its maximum density
|-
| [[Water]] (salt)             || 1,030  || 3%
|-
| [[Liquid oxygen]]            || 1,141  || At approx. −219&nbsp;°C
|-
| [[Nylon]]                    || 1,150  ||
|-
| [[Plastics]]                 || 1,175  || Approx.; for [[polypropylene]] and [[PETE]]/[[PVC]]
|-
| [[Tetrachloroethene]]        || 1,622  ||
|-
| [[Magnesium]]                || 1,740  ||
|-
| [[Beryllium]]                || 1,850  ||
|-
| [[Glycerol]]                 || 1,261  || <ref>[http://physics.nist.gov/cgi-bin/Star/compos.pl?matno=174 glycerol composition at] {{webarchive|url=https://web.archive.org/web/20130228142256/http://physics.nist.gov/cgi-bin/Star/compos.pl?matno=174 |date=February 28, 2013 }}. Physics.nist.gov. Retrieved on July 14, 2012.</ref>
|-
| [[Concrete]]                 || 2,400  || <ref>[https://hypertextbook.com/facts/1999/KatrinaJones.shtml]</ref><ref name="YoungFreedman2012">Hugh D. Young; Roger A. Freedman. ''[https://books.google.com/books?id=1YXznQEACAAJ University Physics with Modern Physics] {{webarchive|url=https://web.archive.org/web/20160430045329/https://books.google.com/books?id=1YXznQEACAAJ |date=April 30, 2016 }}''. Addison-Wesley; 2012. {{ISBN|978-0-321-69686-1}}. p. 374.</ref>
|-
| [[Silicon]]                  || 2,330  ||
|-
| [[Aluminium]]                || 2,700  ||
|-
| [[Diiodomethane]]            || 3,325  || Liquid at room temperature
|-
| [[Diamond]]                  || 3,500  ||
|-
| [[Titanium]]                 || 4,540  ||
|-
| [[Selenium]]                 || 4,800  ||
|-
| [[Vanadium]]                 || 6,100  ||
|-
| [[Antimony]]                 || 6,690  ||
|-
| [[Zinc]]                     || 7,000  ||
|-
| [[Chromium]]                 || 7,200  ||
|-
| [[Tin]]                      || 7,310  ||
|-
| [[Manganese]]                || 7,325  || Approx.
|-
| [[Iron]]                     || 7,870  ||
|-
| [[Niobium]]                  || 8,570  ||
|-
| [[Brass]]                    || 8,600  || <ref name="YoungFreedman2012">Hugh D. Young; Roger A. Freedman. ''[https://books.google.com/books?id=1YXznQEACAAJ University Physics with Modern Physics] {{webarchive|url=https://web.archive.org/web/20160430045329/https://books.google.com/books?id=1YXznQEACAAJ |date=April 30, 2016 }}''. Addison-Wesley; 2012. {{ISBN|978-0-321-69686-1}}. p. 374.</ref>
|-
| [[Cadmium]]                  || 8,650  ||
|-
| [[Cobalt]]                   || 8,900  ||
|-
| [[Nickel]]                   || 8,900  ||
|-
| [[Copper]]                   || 8,940  ||
|-
| [[Bismuth]]                  || 9,750  ||
|-
| [[Molybdenum]]               || 10,220 ||
|-
| [[Silver]]                   || 10,500 ||
|-
| [[Lead]]                     || 11,340 ||
|-
| [[Thorium]]                  || 11,700 ||
|-
| [[Rhodium]]                  || 12,410 ||
|-
| [[Mercury (element)|Mercury]]|| 13,546 ||
|-
| [[Tantalum]]                 || 16,600  ||
|-
| [[Uranium]]                  || 18,800  ||
|-
| [[Tungsten]]                 || 19,300  ||
|-
| [[Gold]]                     || 19,320  ||
|-
| [[Plutonium]]                || 19,840  ||
|-
| [[Rhenium]]                  || 21,020  ||
|-
| [[Platinum]]                 || 21,450  ||
|-
| [[Iridium]]                  || 22,420  ||
|-
| [[Osmium]]                   || 22,570  ||
|-
! <!-- This is a header to stop the notes sorting; this is horrendous --> colspan=3 style="background-color:#f9f9f9; text-align:left; font-weight:normal;" | Notes:
{{reflist|group=note}}
|}
{{Clear}}

=== Others ===
{| class="wikitable sortable" style="text-align:center;"
|-
! Entity
! ''ρ'' (kg/m<sup>3</sup>)
! class="unsortable" | Notes
|-
| [[Interstellar medium]]  || data-sort-value="0.0000000000000000001" | {{val|1|e=-19}} || Assuming 90% H, 10% He; variable T
|-
| The [[Earth]]            || 5,515 || Mean density.<ref>{{citation |url=http://www.wolframalpha.com/input/?i=density+of+the+earth |title=Density of the Earth |publisher=wolframalpha.com |url-status=live |archiveurl=https://web.archive.org/web/20131017051437/http://www.wolframalpha.com/input/?i=density+of+the+earth |archivedate=October 17, 2013 |df=mdy-all }}</ref>
|-
| [[Earth's inner core]] || 13,000 || Approx., as listed in [[Earth]].<ref>{{citation |url=http://www.wolframalpha.com/input/?i=density+of+earth%27s+core |title=Density of Earth's core |publisher=wolframalpha.com |url-status=live |archiveurl=https://web.archive.org/web/20131017051441/http://www.wolframalpha.com/input/?i=density+of+earth%27s+core |archivedate=October 17, 2013 |df=mdy-all }}</ref>
|-
| The core of the [[Sun]]  || 33,000–160,000 || Approx.<ref>{{citation |url=http://www.wolframalpha.com/input/?i=density+of+sun%27s+core |title=Density of the Sun's core |publisher=wolframalpha.com |url-status=live |archiveurl=https://web.archive.org/web/20131017051337/http://www.wolframalpha.com/input/?i=density+of+sun%27s+core |archivedate=October 17, 2013 |df=mdy-all }}</ref>
|-
| [[Supermassive black hole|Super-massive black hole]] || {{val|9|e=5}} || Density of a 4.5-million-solar-mass black hole<br />[[Event horizon]] radius is 13.5 million km.
|-
| [[White dwarf]] star     || {{val|2.1|e=9}} || Approx.<ref name="osln">[http://www.astronomy.ohio-state.edu/~jaj/Ast162/lectures/notesWL22.pdf Extreme Stars: White Dwarfs & Neutron Stars] {{webarchive|url=https://web.archive.org/web/20070925204453/http://www.astronomy.ohio-state.edu/~jaj/Ast162/lectures/notesWL22.pdf |date=September 25, 2007 }}, Jennifer Johnson, lecture notes, Astronomy 162, [[Ohio State University]]. Accessed: May 3, 2007.</ref>
|-
| [[Atomic nuclei]]        || {{val|2.3|e=17}} || Does not depend strongly on size of nucleus<ref>[http://hyperphysics.phy-astr.gsu.edu/HBASE/Nuclear/nucuni.html Nuclear Size and Density] {{webarchive|url=https://web.archive.org/web/20090706034134/http://hyperphysics.phy-astr.gsu.edu/hbase/nuclear/nucuni.html |date=July 6, 2009 }}, HyperPhysics, Georgia State University. Accessed: June 26, 2009.</ref>
|-
| [[Neutron star]]         || {{val|1|e=18}} ||
|-
| Stellar-mass [[black hole]] || {{val|1|e=18}} || Density of a 4-solar-mass black hole<br /> [[Event horizon]] radius is 12&nbsp;km.
|}

=== Water ===
{{See also|Water (molecule)#Density of water and ice|l1=Water density}}

{| class="wikitable" style="text-align:center;"
|+ Density of liquid water at 1 [[Atmosphere (unit)|atm]] pressure
|-
! Temp. (°C)<ref group=note>Values below 0&nbsp;°C refer to [[supercooling|supercooled]] water.</ref>
! Density (kg/m<sup>3</sup>)
|-
| −30 || 983.854
|-
| −20 || 993.547
|-
| −10 || 998.117
|-
| 0   || 999.8395
|-
| 4   || 999.9720
|-
| 10  || 999.7026
|-
| 15  || 999.1026
|-
| 20  || 998.2071
|-
| 22  || 997.7735
|-
| 25  || 997.0479
|-
| 30  || 995.6502
|-
| 40  || 992.2
|-
| 60  || 983.2
|-
| 80  || 971.8
|-
| 100 || 958.4
|-
|colspan=2 |Notes:
{{reflist|group=note}}
|}

=== Air ===
{{Main article|Density of air}}
[[File:Air density vs temperature.svg|thumb|right|400px|Air density ''vs.'' temperature]]

{| class="wikitable" style="text-align:center;"
|+Density of air at 1 [[Atmosphere (unit)|atm]] pressure
|-
! ''T'' (°C)
! ''ρ'' (kg/m<sup>3</sup>)
|-
| −25 || 1.423
|-
| −20 || 1.395
|-
| −15 || 1.368
|-
| −10 || 1.342
|-
| −5  || 1.316
|-
|  0  || 1.293
|-
|  5  || 1.269
|-
|  10 || 1.247
|-
|  15 || 1.225
|-
|  20 || 1.204
|-
|  25 || 1.184
|-
|  30 || 1.164
|-
|  35 || 1.146
|}
{{Clear}}

=== Molar volumes of liquid and solid phase of elements ===
[[File:Molar volumes of liquid and solid phase of elements.jpg|thumb|left|1000px|Molar volumes of liquid and solid phase of elements]]

{{Clear}}

== Common units ==
The [[SI]] unit for density is:
* [[kilogram]] per [[cubic metre]] (kg/m<sup>3</sup>)

The litre and metric tons are not part of the SI, but are acceptable for use with it, leading to the following units:
* [[kilogram]] per [[litre]] (kg/L)
* [[gram]] per [[millilitre]] (g/mL)
* [[metric ton]] per cubic metre (t/m<sup>3</sup>)

Densities using the following metric units all have exactly the same numerical value, one thousandth of the value in (kg/m<sup>3</sup>). Liquid [[water]] has a density of about 1&nbsp;kg/dm<sup>3</sup>, making any of these SI units numerically convenient to use as most [[solid]]s and [[liquid]]s have densities between 0.1 and 20&nbsp;kg/dm<sup>3</sup>.
* kilogram per cubic decimetre (kg/dm<sup>3</sup>)
* gram per cubic centimetre (g/cm<sup>3</sup>)
** 1 g/cm<sup>3</sup> = 1000&nbsp;kg/m<sup>3</sup>
* megagram (metric ton) per cubic metre (Mg/m<sup>3</sup>)

In [[US customary units]] density can be stated in:
* [[Avoirdupois ounce]] per [[cubic inch]] (1 g/cm<sup>3</sup> ≈ 0.578036672 oz/cu&nbsp;in)
* [[Avoirdupois ounce]] per [[fluid ounce]] (1 g/cm<sup>3</sup> ≈ 1.04317556 oz/US fl oz = 1.04317556 lb/US fl pint)
* [[Pound (mass)|Avoirdupois pound]] per cubic inch (1 g/cm<sup>3</sup> ≈ 0.036127292 lb/cu&nbsp;in)
* pound per [[cubic foot]] (1 g/cm<sup>3</sup> ≈ 62.427961 lb/cu&nbsp;ft)
* pound per [[cubic yard]] (1 g/cm<sup>3</sup> ≈ 1685.5549 lb/cu&nbsp;yd)
* pound per [[US liquid gallon]] (1 g/cm<sup>3</sup> ≈ 8.34540445 lb/US gal)
* pound per US [[bushel]] (1 g/cm<sup>3</sup> ≈ 77.6888513 lb/bu)
* [[slug (unit)|slug]] per cubic foot

[[Imperial units]] differing from the above (as the Imperial gallon and bushel differ from the US units) in practice are rarely used, though found in older documents. The Imperial gallon was based on the concept that an [[Imperial fluid ounce]] of water would have a mass of one Avoirdupois ounce, and indeed 1&nbsp;g/cm<sup>3</sup> ≈ 1.00224129 ounces per Imperial fluid ounce = 10.0224129 pounds per Imperial gallon. The density of [[precious metal]]s could conceivably be based on [[Troy weight|Troy]] ounces and pounds, a possible cause of confusion.

== See also ==
{{Div col|colwidth=22em}}
* [[List of elements by density]]
* [[Air density]]
* [[Area density]]
* [[Bulk density]]
* [[Buoyancy]]
* [[Charge density]]
* [[Girolami method|Density prediction by the Girolami method]]
* [[Dord]]
* [[Energy density]]
* [[Lighter than air]]
* [[Linear density]]
* [[Number density]]
* [[Orthobaric density]]
* [[Paper density]]
* [[Specific weight]]
* [[Spice (oceanography)]]
* [[Standard temperature and pressure]]
{{Div col end}}

== References ==
{{Reflist|40em}}

== External links ==
* {{cite EB1911|wstitle=Density |volume=8 |short=x}}
* {{Cite NSRW|wstitle=Density |short=x}}
* [https://www.youtube.com/watch?v=eY-44iPSWIU Video: Density Experiment with Oil and Alcohol]
* [https://www.youtube.com/watch?v=96NFH2Z7GSA Video: Density Experiment with Whiskey and Water]
* [http://glassproperties.com/density/room-temperature/ Glass Density Calculation – Calculation of the density of glass at room temperature and of glass melts at 1000 – 1400°C]
* [http://www.science.co.il/PTelements.asp?s=Density List of Elements of the Periodic Table – Sorted by Density]
* [http://ddbonline.ddbst.de/DIPPR105DensityCalculation/DIPPR105CalculationCGI.exe Calculation of saturated liquid densities for some components]
* [http://www.denichsoiltest.com/field/field-density-test.html Field density test]
* [http://www.aim.env.uea.ac.uk/aim/density/density_eletrolyte.php On-line calculator for densities and partial molar volumes of aqueous solutions of some common electrolytes and their mixtures, at temperatures up to 323.15 K.]{{dead link|date=March 2018 |bot=InternetArchiveBot |fix-attempted=yes }}
* [http://www.engineeringtoolbox.com/water-density-specific-weight-d_595.html Water – Density and specific weight]
* [http://www.sengpielaudio.com/ConvDensi.htm Temperature dependence of the density of water – Conversions of density units]
* [http://www.adamequipment.com/education/Documents/EdExp1.pdf A delicious density experiment]
* [http://linkingweatherandclimate.com/ocean/waterdensitycalc.php Water density calculator] Water density for a given salinity and temperature.
* [http://www.enggcyclopedia.com/welcome-to-enggcyclopedia/calculators/liquid-density Liquid density calculator] Select a liquid from the list and calculate density as a function of temperature.
* [http://www.enggcyclopedia.com/welcome-to-enggcyclopedia/thermodynamics/gas-density Gas density calculator] Calculate density of a gas for as a function of temperature and pressure.
* [http://www.jaredzone.info/2010/09/densities.html Densities of various materials.]
* [http://amrita.olabs.co.in/?sub=1&brch=1&sim=2&cnt=9 Determination of Density of Solid], instructions for performing classroom experiment.
* [http://www.shd.org.rs/JSCS/Vol75/No2/13_4388_3960.pdf density prediction]
* [http://www.scielo.cl/scielo.php?pid=S0717-97072008000100015&script=sci_arttext density prediction]

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[[Category:Density| ]]
[[Category:Physical quantities]]