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# Encyclopedia

### From Wikipedia, the free encyclopedia

.The density of a material is defined as its mass per unit volume.^ Mass of a substance per unit volume.
• General Chemistry Online: Glossary: 19 January 2010 18:22 UTC antoine.frostburg.edu [Source type: Academic]

^ Density is mass per unit volume.
• Polyurethane Foam Association 19 January 2010 18:22 UTC www.pfa.org [Source type: FILTERED WITH BAYES]

^ In other words, we need to compare the masses-per-unit-volume, meaning the densities , of each material with that of water.
• Understanding density and buoyancy 19 January 2010 18:22 UTC www.chem1.com [Source type: Academic]

.The symbol of density is ρ (the Greek letter rho).^ Greek letter rho .
• Density of Matter - Succeed in Understanding Physics: School for Champions 19 January 2010 18:22 UTC www.school-for-champions.com [Source type: FILTERED WITH BAYES]

^ Density (symbol: ρ - Greek : rho ) is a measure of mass per unit of volume .
• Density (chemistry) - encyclopedia article - Citizendium 19 January 2010 18:22 UTC en.citizendium.org [Source type: Academic]

^ For other meanings of density, see density (disambiguation) Density (symbol: ρ - Greek : rho) is a measure of mass per unit of volume .

## Formula

Mathematically:
$\rho = \frac{m}{V} \,$
where:
ρ (rho) is the density,
m is the mass,
V is the volume.
.Different materials usually have different densities, so density is an important concept regarding buoyancy, metal purity and packaging.^ The purpose of this lesson is to show how densities are defined, measured, and utilized, and to make sure you understand the closely-related concepts of buoyancy and specific gravity .
• Understanding density and buoyancy 19 January 2010 18:22 UTC www.chem1.com [Source type: Academic]

^ Water is the most important liquid on earth; density currents are common where waters of two different densities meet.
• Density currents 19 January 2010 18:22 UTC www.beloit.edu [Source type: FILTERED WITH BAYES]

^ Lead shot can be obtained at a gun and ammo shop), any other finely ground solid material which can be used to illustrate a variety of different densities.
• Background on Mass, Weight and Density 19 January 2010 18:22 UTC www.physics.ucla.edu [Source type: FILTERED WITH BAYES]

.In some cases density is expressed as the dimensionless quantities specific gravity (SG) or relative density (RD), in which case it is expressed in multiples of the density of some other standard material, usually water or air/gas.^ The relative densities of gases are usually expressed in terms of the standard gas under the same conditions.

^ Most densities of liquids are compare to the density of water, and this is called specific gravity.

^ Relative Density: the density of a material relative to another material, commonly water.
• Project Labs - Density 19 January 2010 18:22 UTC www.projectlabs.com [Source type: FILTERED WITH BAYES]

## History

.In a well-known tale, Archimedes was given the task of determining whether King Hiero's goldsmith was embezzling gold during the manufacture of a wreath dedicated to the gods and replacing it with another, cheaper alloy.^ The most famous application of buoyancy is due to Archimedes of Syracuse around 250 BC. He was asked to determine whether the new crown that King Hiero II had commissioned contained all the gold that he had provided to the goldsmith for that purpose; apparently he suspected that the smith might have set aside some of the gold for himself and substituted less-valuable silver instead.
• Understanding density and buoyancy 19 January 2010 18:22 UTC www.chem1.com [Source type: Academic]

[1]
.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.^ Calculate its volume and then determine its mass.

^ Object with three dimensions such as a cube, cylinder, sphere    or other objects whose volume can be determined with a ruler.

^ In previous sim panels, they would be able to get density of gold and silver, and then in this panel, they would be able to put crown into water and measure its volume and also weigh it outside of the tub, so they calculate its density.
• Density - Sim Design 19 January 2010 18:22 UTC docs.google.com [Source type: FILTERED WITH BAYES]

.Baffled, Archimedes took a relaxing immersion bath and observed from the rise of the warm water upon entering that he could calculate the volume of the gold crown through the displacement of the water.^ Determine the volume of the rocks by the displacement of water.

^ Calculate the difference between the final and initial volumes to determine the volume of water displaced; enter this value in Table 2.
• Figure 1 Set-up Hint 19 January 2010 18:22 UTC chemlab.truman.edu [Source type: Academic]

^ For an irregular solid such as a rock, this is most easily done by observing the amount of water it displaces.
• Understanding density and buoyancy 19 January 2010 18:22 UTC www.chem1.com [Source type: Academic]

.Allegedly, upon this discovery, he went running naked through the streets shouting, "Eureka!^ Legend has it that Archimedes was so excited about his discovery that he ran naked through the streets of Sicily shouting "Eureka!

^ The story goes that he was so enthused with his discovery that he jumped out of his bath and ran through the town, shouting "eureka" to the bemused people.
• Understanding density and buoyancy 19 January 2010 18:22 UTC www.chem1.com [Source type: Academic]

Eureka!" (Εύρηκα! Greek "I found it"). .As a result, the term "eureka" entered common parlance and is used today to indicate a moment of enlightenment.^ These differences are small and indicate that no significant deviations between the LDA and VMC results are likely to be resolved by using a larger cell.
• 7.3 The density matrix and natural orbitals 19 January 2010 18:22 UTC www.physics.uc.edu [Source type: Academic]

.The story first appeared in written form in Vitruvius' books of architecture, two centuries after it supposedly took place.^ Fourth Week: We Look for "Proper Places" of Different Liquids, and Try to Refloat the Wood Two major activities took place in this session.

[2] .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.^ In this group, the first one happened to catch on: why some things float and not others.

^ Others say mass is the measure of an object's inertia (which assumes we understand the elusive property of inertia).
• Background on Mass, Weight and Density 19 January 2010 18:22 UTC www.physics.ucla.edu [Source type: FILTERED WITH BAYES]

^ Either way, this puzzle would require some guidance/instruction.
• Density - Sim Design 19 January 2010 18:22 UTC docs.google.com [Source type: FILTERED WITH BAYES]

[3][4]

## Measurement of density

.For a homogeneous object, the mass divided by the volume gives the density.^ Similarly, changing an object's volume should change its mass (at constant density).
• Density - Sim Design 19 January 2010 18:22 UTC docs.google.com [Source type: FILTERED WITH BAYES]

^ The density of a quantity of matter is its mass divided by its volume.
• Density of Matter - Succeed in Understanding Physics: School for Champions 19 January 2010 18:22 UTC www.school-for-champions.com [Source type: FILTERED WITH BAYES]

^ Density is mass per volume.
• Background on Mass, Weight and Density 19 January 2010 18:22 UTC www.physics.ucla.edu [Source type: FILTERED WITH BAYES]

.The mass is normally measured with an appropriate scale or balance; the volume may be measured directly (from the geometry of the object) or by the displacement of a fluid.^ Measuring mass: Mass is usually measured with a balance.
• Background on Mass, Weight and Density 19 January 2010 18:22 UTC www.physics.ucla.edu [Source type: FILTERED WITH BAYES]

^ The weight may be directly determined by the balance.

^ The volume of fluid displaced by a fully submerged object depends on its mass or density, or the density of the fluid.
• Density - Sim Design 19 January 2010 18:22 UTC docs.google.com [Source type: FILTERED WITH BAYES]

.Hydrostatic weighing is a method that combines these two.^ Practical Determination Of Densities The methods for determining densities may be divided into two groups according as hydrostatic principles are employed or not.

^ The method of "hydrostatic weighing" is one of the most important.

.If the body is not homogeneous, then the density is a function of the position: $\rho(\vec{r})=dm/dv$, where dv is an elementary volume at position $\vec{r}$.^ Density offers a convenient means of obtaining the mass of a body from its volume or vice versa; the mass is equal to the volume multiplied by the density, while the volume is equal to the mass divided by the density.
• density (chemistry and physics) -- Britannica Online Encyclopedia 19 January 2010 18:22 UTC www.britannica.com [Source type: Academic]

^ For a homogeneous solid object, the mass divided by the volume gives the density.
• Density (chemistry) - encyclopedia article - Citizendium 19 January 2010 18:22 UTC en.citizendium.org [Source type: Academic]

The mass of the body then can be expressed as
$m = \int_V \rho(\vec{r}) dV.$
.The density of a solid material can be ambiguous, depending on exactly how its volume is defined, and this may cause confusion in measurement.^ Given the density and volume of a material, how do you find its mass?
• Density of Matter - Succeed in Understanding Physics: School for Champions 19 January 2010 18:22 UTC www.school-for-champions.com [Source type: FILTERED WITH BAYES]

^ However, the density of a solid material can be defined in several ways.
• Density (chemistry) - encyclopedia article - Citizendium 19 January 2010 18:22 UTC en.citizendium.org [Source type: Academic]

^ Find the volume and density of irregular solids.

.A common example is sand: if it is gently poured into a container, the density will be low; if the same sand is compacted into the same container, it will occupy less volume and consequently exhibit a greater density.^ Do not pour water containing sediment into sinks because it will clog drains.
• Density currents 19 January 2010 18:22 UTC www.beloit.edu [Source type: FILTERED WITH BAYES]

^ Thus a more dense material occupies less volume than does the same weight of a less dense material.
• Project Labs - Density 19 January 2010 18:22 UTC www.projectlabs.com [Source type: FILTERED WITH BAYES]

^ In previous sim panels, they would be able to get density of gold and silver, and then in this panel, they would be able to put crown into water and measure its volume and also weigh it outside of the tub, so they calculate its density.
• Density - Sim Design 19 January 2010 18:22 UTC docs.google.com [Source type: FILTERED WITH BAYES]

.This is because sand, like all powders and granular solids, contains a lot of air space in between individual grains.^ This often occurs object is constructed with a large volume with little additional mass (lots of air or vacuum space).

^ They should either conclude on their own or will be told that the low bulk density occurs because there is air between the particles.
• Project Labs - Density 19 January 2010 18:22 UTC www.projectlabs.com [Source type: FILTERED WITH BAYES]

^ The method involves three operations: - (1) weighing the solid in air (W), (2) weighing the specific gravity bottle full of liquid (W 1), (3) weighing the bottle containing the solid and filled up with liquid (W2).

.The density of the material including the air spaces is the bulk density, which differs significantly from the density of an individual grain of sand with no air included.^ Bulk density: the average density of a material which consists of individual macroscopic particles, i.e.
• Project Labs - Density 19 January 2010 18:22 UTC www.projectlabs.com [Source type: FILTERED WITH BAYES]

^ The density of the sand grains, exclusive of the air between the grains, will be higher than the bulk density.
• Density (chemistry) - encyclopedia article - Citizendium 19 January 2010 18:22 UTC en.citizendium.org [Source type: Academic]

^ We hope we can explain the difference between mass, weight and density so clearly that you will have no trouble explaining the difference to your students.
• Background on Mass, Weight and Density 19 January 2010 18:22 UTC www.physics.ucla.edu [Source type: FILTERED WITH BAYES]

## Formal definition

.Density is defined as mass per unit volume.^ Density is mass divided by displaced volume.

^ Density is mass per volume.
• Background on Mass, Weight and Density 19 January 2010 18:22 UTC www.physics.ucla.edu [Source type: FILTERED WITH BAYES]

^ The higher an object's density, the higher its mass per volume .
• Density (chemistry) - encyclopedia article - Citizendium 19 January 2010 18:22 UTC en.citizendium.org [Source type: Academic]

A concise statement of what this means may be obtained by considering a small box in a Cartesian coordinate system, with dimensions Δx, Δy, Δz. If the mass is represented by a net mass function, then the density at some point (x,y,z) is:
\begin{align} \rho(x,y,z) & = \lim_{Volume o 0}\frac{\mbox{mass of box}}{\mbox{volume of box}} \ & = \lim_{\Delta x, \Delta y, \Delta z o 0}\left(\frac{ m(x + \Delta x, y + \Delta y, z + \Delta z) - m(x, y, z)}{\Delta x \Delta y \Delta z}\right) \ & = \frac{d m}{d V}.\ \end{align}\,
.For a homogeneous substance, this derivative is equal to the net mass divided by the net volume.^ The density of an object equals its total mass divided by its total volume.
• Density (chemistry) - encyclopedia article - Citizendium 19 January 2010 18:22 UTC en.citizendium.org [Source type: Academic]

^ To determine density of a substance, divide its mass by   its volume.

^ Density is mass divided by displaced volume.

For a nonhomogeneous substance, m is a nonconstant function of position: m = m(x,y,z).

## Common units

The SI unit for density is:
.Densities using the following metric units all have exactly the same numerical value, one thousandth of the value in (kg/m³).^ Minimum value of parameters to be used in gamln() Definition at line 44 of file Density.cpp .
• mcmc: Density Namespace Reference 19 January 2010 18:22 UTC darwin.eeb.uconn.edu [Source type: Reference]

^ One could easily use a dollars per milligram instead, in which case the stamp would hold it's value at that level, since it weighs more.
• The monetary density of things - Evil Mad Scientist Laboratories 19 January 2010 18:22 UTC www.evilmadscientist.com [Source type: FILTERED WITH BAYES]

^ Now that we have the pressure due to water vapor and also the pressure due to the dry air, we have all of the information that is required to calculate the air density using equation 4a.
• Equations - Air Density and Density Altitude 19 January 2010 18:22 UTC wahiduddin.net [Source type: Academic]

.Liquid water has a density of about 1 kg/dm³, making any of these SI units numerically convenient to use as most solids and liquids have densities between 0.1 and 20 kg/dm³.^ The SI unit of density is the kilogram per cubic metre ( kg / m 3 ): .
• Density (chemistry) - encyclopedia article - Citizendium 19 January 2010 18:22 UTC en.citizendium.org [Source type: Academic]

^ The density of solids and liquids are usually stated in g/cm 3 , while gases are usually in kg/m 3 .
• Density of Matter - Succeed in Understanding Physics: School for Champions 19 January 2010 18:22 UTC www.school-for-champions.com [Source type: FILTERED WITH BAYES]

^ What is your conclusion about the density of water?

• kilograms per cubic decimeter (kg/dm³)
• grams per cubic centimeter (g/cc, gm/cc or g/cm³)
• megagrams per cubic meter (Mg/m³)
Liters and metric tons are not part of the SI, but are acceptable for use with it. Since 1 L = 1 dm³, we also have these of the same size:
In U.S. customary units density can be stated in:
.In principle there are Imperial units different from the above as the Imperial gallon and bushel differ from the U.S. units, but in practice they are no longer used, though found in older documents.^ And if there's no music, they can't dance.
• Back to the Future (1985) - Memorable quotes 19 January 2010 18:22 UTC www.imdb.com [Source type: General]

^ In Imperial units or U.S. customary units , the units of density include pounds per cubic foot (lb/ft 3 ), pounds per cubic yard (lb/yd 3 ), pounds per cubic inch (lb/in 3 ), ounces per cubic inch (oz/in 3 ), pounds per gallon (lb/gal) for both the Imperial and the U.S. gallon, pounds per U.S. bushel (lb/bu), slugs per cubic foot (slugs/ft 3 ), and others.
• Density (chemistry) - encyclopedia article - Citizendium 19 January 2010 18:22 UTC en.citizendium.org [Source type: Academic]

^ Furthermore, there is no basis whatsoever to compare housing types based on energy use per unit of floor area, as in the cited article.
• The Case for Density in Sustainable Cities | Planetizen 19 January 2010 18:22 UTC www.planetizen.com [Source type: FILTERED WITH BAYES]

.The density of precious metals could conceivably be based on Troy ounces and pounds, a possible cause of confusion.^ US gallon = 128 US fluid ounces You could write a whole-nuther entire article using bottled water as the base instead of a pound of gold.
• The monetary density of things - Evil Mad Scientist Laboratories 19 January 2010 18:22 UTC www.evilmadscientist.com [Source type: FILTERED WITH BAYES]

## Changes of density

.In general, density can be changed by changing either the pressure or the temperature.^ If the air pressure changes, due to temperature or humidity, then an aircraft altimeter will of course change to indicate the actual air pressure.
• Equations - Air Density and Density Altitude 19 January 2010 18:22 UTC wahiduddin.net [Source type: Academic]

^ Liquid densities are largely independent of pressure, but they are somewhat temperature-sensitive.
• Understanding density and buoyancy 19 January 2010 18:22 UTC www.chem1.com [Source type: Academic]

^ Here's a calculator that uses the actual pressure, air temperature and dew point to calculate the air density as well as the corresponding density altitude: .
• Equations - Air Density and Density Altitude 19 January 2010 18:22 UTC wahiduddin.net [Source type: Academic]

.Increasing the pressure will always increase the density of a material.^ If solid material is mixed into the water, then the density increases.
• Density currents 19 January 2010 18:22 UTC www.beloit.edu [Source type: FILTERED WITH BAYES]

.Increasing the temperature generally decreases the density, but there are notable exceptions to this generalisation.^ Would that increase or decrease the   density?

^ Without a change in land area or forage growth a decrease in forage allowance occurs, and a de facto increase in stocking density even though cow numbers and land area have not changed.
• AN155/AN155: Pasture Stocking Density and the Relationship to Animal Performance 19 January 2010 18:22 UTC edis.ifas.ufl.edu [Source type: Academic]

^ However, there are many forms of simpler approximations and generalizations that have been developed over the years, but please note that they are not really the density altitude, they are just numbers that approximate the density altitude.
• Equations - Air Density and Density Altitude 19 January 2010 18:22 UTC wahiduddin.net [Source type: Academic]

.For example, the density of water increases between its melting point at 0 °C and 4 °C; similar behaviour is observed in silicon at low temperatures.^ If solid material is mixed into the water, then the density increases.
• Density currents 19 January 2010 18:22 UTC www.beloit.edu [Source type: FILTERED WITH BAYES]

^ Figure 3 is an example of the variation in animal performance across years between low and high stocking densities.
• AN155/AN155: Pasture Stocking Density and the Relationship to Animal Performance 19 January 2010 18:22 UTC edis.ifas.ufl.edu [Source type: Academic]

^ They should either conclude on their own or will be told that the low bulk density occurs because there is air between the particles.
• Project Labs - Density 19 January 2010 18:22 UTC www.projectlabs.com [Source type: FILTERED WITH BAYES]

.The effect of pressure and temperature on the densities of liquids and solids is small.^ Densities of substances and materials Solids, liquids and gases .
• Understanding density and buoyancy 19 January 2010 18:22 UTC www.chem1.com [Source type: Academic]

^ Now armed with those equations and the actual air pressure, the vapor pressure and the temperature, the density of the air can be calculated.
• Equations - Air Density and Density Altitude 19 January 2010 18:22 UTC wahiduddin.net [Source type: Academic]

^ It is readily seen that W+W i - W 2 is the weight of the liquid displaced by the solid, and therefore is the weight of an equal volume of liquid; hence the relative density is W/(W+Wi - W2).

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.
In contrast, the density of gases is strongly affected by pressure. The density of an ideal gas is
$\rho = \frac {MP}{RT} \,$
where .R is the universal gas constant, P is the pressure, M is the molar mass, and T is the absolute temperature.^ To the extent that a gas exhibits ideal behavior (low pressure, high temperature), the density of a gas is directly proportional to the masses of its component atoms, and thus to its molecular weight.
• Understanding density and buoyancy 19 January 2010 18:22 UTC www.chem1.com [Source type: Academic]

^ Whenever stating the density of a gas, it is important that the reference temperature and pressure (at which that density was obtained or calculated) be explicitly stated.
• Density (chemistry) - encyclopedia article - Citizendium 19 January 2010 18:22 UTC en.citizendium.org [Source type: Academic]

^ In expressing the absolute or relative density of any substance, it is necessary to specify the conditions for which the relation holds: in the case of gases, the temperature and pressure of the experimental gas (and of the standard, in the case of relative density); and in the case of solids and liquids, the temperature.

.This means that the density of an ideal gas can be doubled by doubling the pressure, or by halving the absolute temperature.^ It may be noted that if comparison be made with water at 4°, the relative density is the same as the absolute density, since the unit of mass in the C.G.S. system is the weight of a cubic centimetre of water at this temperature.

^ Liquid densities are largely independent of pressure, but they are somewhat temperature-sensitive.
• Understanding density and buoyancy 19 January 2010 18:22 UTC www.chem1.com [Source type: Academic]

^ Here's a calculator that uses the actual pressure, air temperature and dew point to calculate the air density as well as the corresponding density altitude: .
• Equations - Air Density and Density Altitude 19 January 2010 18:22 UTC wahiduddin.net [Source type: Academic]

.Osmium is the densest known substance at standard conditions for temperature and pressure.^ The temperature of the experimental substance may or may not be the temperature of the standard.

^ In expressing the absolute or relative density of any substance, it is necessary to specify the conditions for which the relation holds: in the case of gases, the temperature and pressure of the experimental gas (and of the standard, in the case of relative density); and in the case of solids and liquids, the temperature.

^ The vessel is then lowered into a jacket containing vapour at a known temperature which is sufficient to volatilize the substance.

## Density of water

See also: Water density
Temp (°C) Density (kg/m3)
100 958.4
80 971.8
60 983.2
40 992.2
30 995.6502
25 997.0479
22 997.7735
20 998.2071
15 999.1026
10 999.7026
4 999.9720
0 999.8395
−10 998.117
−20 993.547
−30 983.854
.The density of water in kilograms per cubic meter (SI unit)
at various temperatures in degrees Celsius.
^ Nature has conveniently made the density of water at ordinary temperatures almost exactly 1.000 g/mL ( 1 kg/L).
• Understanding density and buoyancy 19 January 2010 18:22 UTC www.chem1.com [Source type: Academic]

^ Related terms: Celsius , Fahrentheit , and Kelvin DEGREE DAY A measure of the departure of the mean daily temperature from a given standard.
• weather.com - Glossary 19 January 2010 18:22 UTC www.weather.com [Source type: FILTERED WITH BAYES]

^ In other words, we need to compare the masses-per-unit-volume, meaning the densities , of each material with that of water.
• Understanding density and buoyancy 19 January 2010 18:22 UTC www.chem1.com [Source type: Academic]

The values below 0 °C refer to supercooled water.

## Density of air

T in °C ρ in kg/m3 (at 1 atm)
–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

## Density of solutions

The density of a solution is the sum of mass (massic) concentrations of the components of that solution.
.Mass (massic) concentration of a given component ρi in a solution can be called partial density of that component.^ There should be controls for changing the volume, mass and density of a given object.
• Density - Sim Design 19 January 2010 18:22 UTC docs.google.com [Source type: FILTERED WITH BAYES]

^ The equation, ratio or fraction for density, also called mass per unit volume   of a substance, is: .

$\rho = \sum_i \rho_i \,$

## Density of composite material

.ASTM specification D792-00[5] describes the steps to measure the density of a composite material.^ All groups should get approximately the same results if the differences in densities between materials are not too small to measure.
• Project Labs - Density 19 January 2010 18:22 UTC www.projectlabs.com [Source type: FILTERED WITH BAYES]

^ By using a scale or a primary balance with weights and by measuring volume, the students can obtain the numerical values needed to calculate the bulk density of materials.
• Project Labs - Density 19 January 2010 18:22 UTC www.projectlabs.com [Source type: FILTERED WITH BAYES]

$\rho = \frac{W_a}{W_a + W_w - W_b} \left (0.9975 \right ) \,$
where:
ρ is the density of the composite material, in g/cm3
and
Wa is the weight of the specimen when hung in the air
Ww is the weight of the partly immersed wire holding the specimen
Wb is the weight of the specimen when immersed fully in distilled water, along with the partly immersed wire holding the specimen
0.9975 is the density in g/cm3 of the distilled water at 23 °C.

## Densities of various materials

Material ρ in kg/m3 Notes
Interstellar medium 10−25 − 10−15 Assuming 90% H, 10% He; variable T
Earth's atmosphere 1.2 At sea level
Aerogel 1 − 2
Styrofoam 30 − 120 From
Cork 220 − 260 From
Water 1000 At STP
Plastics 850 − 1400 For polypropylene and PETE/PVC
Glycerol[6][7] 1261
The Earth 5515.3 Mean density
Iron 7874 Near room temperature
Copper 8920 − 8960 Near room temperature
Lead 11340 Near room temperature
The Inner Core of the Earth ~13000 As listed in Earth
Uranium 19100 Near room temperature
Tungsten 19250 Near room temperature
Gold 19300 Near room temperature
Platinum 21450 Near room temperature
Iridium 22500 Near room temperature
Osmium 22610 Near room temperature
The core of the Sun ~150000
White dwarf star 1 × 109[8]
Atomic nuclei 2.3 × 1017 [9] Does not depend strongly on size of nucleus
Neutron star 8.4 × 1016 — 1 × 1018
Black hole 4 × 1017 Mean density inside the Schwarzschild radius of an earth-mass black hole (theoretical)

## References

1. ^ Archimedes, A Gold Thief and Buoyancy - by Larry "Harris" Taylor, Ph.D.
2. ^ Vitruvius on Architecture, Book IX, paragraphs 9-12, translated into English and in the original Latin.
3. ^ The first Eureka moment, Science 305: 1219, August 2004.
4. ^ Fact or Fiction?: Archimedes Coined the Term "Eureka!" in the Bath, Scientific American, December 2006.
5. ^ (2004). Test Methods for Density and Specific Gravity (Relative Density) of Plastics by Displacement. ASTM Standard D792-00. Vol 81.01. American Society for Testing and Materials. West Conshohocken. PA.
6. ^ glycerol composition at physics.nist.gov
7. ^ Glycerol density at answers.com
8. ^ Extreme Stars: White Dwarfs & Neutron Stars, Jennifer Johnson, lecture notes, Astronomy 162, Ohio State University. Accessed on line May 3, 2007.
9. ^ Nuclear Size and Density, HyperPhysics, Georgia State University. Accessed on line June 26, 2009.

# 1911 encyclopedia

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# Simple English

Density is a measurement that compares the amount, ratio, of matter an object has to its volume. An object with a lot of matter in a certain amount of volume has high density. An object with a little matter in the same amount of volume has a low density.

Temperature has an effect on density. When the temperature of a substance increases,the density decreases. When the temperature of a substance of a substance decreases, the density increases. Many substances follow this rule, but there are exceptions. Water is one such exception. Fresh water is the only liquid with a density of 1.

The most common SI units for density are g/cm3 and kg/m3. When the numerator is much larger than the denominator, that means the substance has a higher density. When the denominator is much larger than the numerator, the substance has a lower density.

A formula to find out density is:

$density = mass / volume$

Sometimes scientists use the idea of density to talk about other properties instead of mass. They're trying to describe how much of a property can be found in a specific piece of what they are looking at. For example, population density is how many people live within the same amount of space. The population density in the city is higher than the country side because there are more people living closer to each other in the city. In computers, storage density is how much data can fit on disks in relation to their physical size. A blu-ray disc has a higher storage density than a DVD which has a higher storage density a CD, even though they all have almost exactly the same volume.

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