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Encyclopedia > Density

In physics the density (ρ) of a body is the ratio of its mass (m) to its volume (V), a measure of how tightly the matter within it is packed together[1]. Its SI units are kilograms per cubic metre (kg/m³). It is also sometimes given in the cgs units of grams per cubic centimetre (g/cm³). The word density or dense has a variety of senses in the physical, mathematical, and quantitative sciences. ... A magnet levitating above a high-temperature superconductor demonstrates the Meissner effect. ... A physical body is an object which can be described by the theories of classical mechanics, or quantum mechanics, and experimented upon by physical instruments. ... This article is about the mathematical concept. ... For other uses, see Mass (disambiguation). ... For other uses, see Volume (disambiguation). ... This article is about matter in physics and chemistry. ... Look up si, Si, SI in Wiktionary, the free dictionary. ... Kg redirects here. ... The cubic meter (symbol mÂ³) is the SI derived unit of volume. ... This article or section is in need of attention from an expert on the subject. ... BIC pen cap, about 1 gram. ... A cubic centimetre (cm3) is an SI derived unit of volume, equal to the volume of a cube with side length of 1 centi metre. ...

Density is defined by:

$rho = frac{m}{V}$

Various substances have different densities, and it is this quantity that determines how they interact when mixed together. For example, in SI units the density of lead is 11.35 x 103, that of water is 1 x 103, and that of cork is 0.24 x 103. The lead has a greater density than water so it sinks; the cork has a smaller density so it floats[2]. General Name, Symbol, Number lead, Pb, 82 Chemical series Post-transition metals or poor metals Group, Period, Block 14, 6, p Appearance bluish gray Standard atomic weight 207. ... Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ... For other uses, see Cork. ...

In some cases the density is expressed as a specific gravity or relative density, in which case it is expressed in multiples of the density of some other standard material, usually water or air. Relative density (also known as specific gravity) is a measure of the density of a material. ... For explanation of specific gravity as it relates to renal function, see Specific gravity (kidney). ...

In a well known problem, 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.[3] For other uses, see Archimedes (disambiguation). ... Grave monument of HiÃ«ro II in Syracuse Hiero II, tyrant of Syracuse from 270 to 215 BC, was the illegitimate son of a Syracusan noble, Hierocles, who claimed descent from Gelo. ... A goldsmith creating a new ring A goldsmith is a metalworker who specializes in working with precious metals, usually to make jewelry. ... GOLD refers to one of the following: GOLD (IEEE) is an IEEE program designed to garner more student members at the university level (Graduates of the Last Decade). ... Steel is a metal alloy whose major component is iron, with carbon content between 0. ...

Archimedes knew that the irregular shaped wreath could be smashed into a cube or sphere, where the volume could be calculated more easily when compared with the weight; the king did not approve of this.

Baffled, Archimedes went to take a bath and observed from the rise of the water upon entering that he could calculate the volume of the crown through the displacement of the water. Allegedly, upon this discovery, Archimedes went running though the streets in the nude shouting, "Eureka! Eureka!" (Greek "I have found it"). As a result, the term "eureka" entered common parlance and is used today to indicate a moment of enlightenment. In fluid mechanics, displacement occurs when an object is immersed in a fluid, pushing it out of the way and taking its place. ... Eureka (Eureka!, or Heureka; Greek (later ); IPA: (modern Greek), (ancient Greek, both former and later forms), Anglicised as ) is a famous exclamation attributed to Archimedes. ...

This story first appeared in written form in Vitruvius' books of architecture, two centuries after it supposedly took place.[4] 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.[5] Marcus Vitruvius Pollio (born c. ... De architectūra (Latin: On architecture) was a treatise on architecture written by the Roman architect Vitruvius and dedicated to his patron, the emperor Caesar Augustus. ...

## Measurement of density

For a homogeneous object, the mass divided by the volume gives the density. If the object has a varying mass, this prescription gives the average density. 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 liquid. Look up Homogeneous in Wiktionary, the free dictionary. ... Digital kitchen scales. ...

A very common instrument for the direct measurement of the density of a liquid is the hydrometer. A less common device for measuring fluid density is a pycnometer, a similar device for measuring the absolute density of a solid is a gas pycnometer. Another instrument used to determine the density of a liquid or a gas is the digital density meter - based on the oscillating U-tube principle. A hydrometer is an instrument used to measure the specific gravity (or relative density) of liquids; that is, the ratio of the density of the liquid to the density of water. ... The pycnometer or pyknometer is a device used for measuring fluid density, also known as a specific gravity bottle. ... For other uses, see Liquid (disambiguation). ... For other uses, see Gas (disambiguation). ... Digital density measuring principle Digital density meter with oscillating U-tube installed With the oscillating U-tube principle, the density of liquids and gases is determined based on an electronic measurement of the frequency of oscillation, from which the density value is calculated. ...

The density of a solid material can be ambiguous, depending on exactly how it is defined, and this may cause confusion in measurement. A common example is sand: if gently filled into a container, the density will be small; when the same sand is compacted into the same container, it will occupy less volume and consequently carry a greater density. This is because "sand" contains a lot of air space in between individual grains; this overall density is called the bulk density, which differs significantly from the density of an individual grain of sand. Bulk density a property of particulate materials. ...

## Common units

SI units for density are: Look up si, Si, SI in Wiktionary, the free dictionary. ...

Units outside the SI Kg redirects here. ... The cubic meter (symbol mÂ³) is the SI derived unit of volume. ... BIC pen cap, about 1 gram. ... A cubic centimetre (cm3) is an SI derived unit of volume, equal to the volume of a cube with side length of 1 centi metre. ...

They also happen to be numerically equivalent to kg/L (1 kg/L = 1 g/cm³ = 1 g/mL). Kg redirects here. ... The litre or liter (see spelling differences) is a unit of volume. ... Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ... BIC pen cap, about 1 gram. ... The millilitre is the equivalent of a cubic centimetre. ...

In U.S. customary units or Imperial units, the units of density include: The U.S. customary units (more commonly known in the US as English units or standard units) are the non-metric units of measurement that are presently used in the United States, in some cases alongside the metric system of units. ... The Imperial units are an irregularly standardized system of units that have been used in the United Kingdom and its former colonies, including the Commonwealth countries. ...

This article is about Ounce (unit of mass). ... A cubic inch is the volume of a cube which is one inch long on each edge. ... Look up pound in Wiktionary, the free dictionary. ... The cubic foot is an imperial and US customary (non-metric) unit of volume, used in the United States, Canada and the United Kingdom. ... The cubic yard (symbols ydÂ³, cu. ... The gallon (abbreviation: gal) is a unit of volume. ... Imperial Measure was a former system of measurement used in some Commonwealth nations, most notably the United Kingdom and Canada. ... A table of weights from the secretaries of the different states, showing the no. ... The slug is an English unit of mass. ...

## Changes of density

In general density can be changed by changing either the pressure or the temperature. Increasing the pressure will always increase the density of a material. Increasing the temperature generally decreases the density, but there are notable exceptions to this generalisation. For example, the density of water increases between its melting point at 0 °C and 4 °C and similar behaviour is observed in silicon at low temperatures. This article is about pressure in the physical sciences. ... For other uses, see Temperature (disambiguation). ... Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ... Not to be confused with Silicone. ...

The effect of pressure and temperature on the densities of liquids and solids is small so that a typical compressibility for a liquid or solid is 10–6 bar–1 (1 bar=0.1 MPa) and a typical thermal expansivity is 10–5 K–1. Fluid Dynamics Compressibility (physics) is a measure of the relative volume change of fluid or solid as a response to a pressure (or mean stress) change: . For a gas the magnitude of the compressibility depends strongly on whether the process is adiabatic or isothermal, while this difference is small in... The bar (symbol bar), decibar (symbol dbar) and the millibar (symbol mbar, also mb) are units of pressure. ... In physics, thermal expansion is the tendency of matter to increase in volume or pressure when heated. ... For other uses, see Kelvin (disambiguation). ...

In contrast, the density of gases is strongly affected by pressure. Boyle's law says that the density of an ideal gas is given by Boyles law (sometimes referred to as the Boyle-Mariotte law) is one of the gas laws and basis of derivation for the ideal gas law, which describes the relationship between the product pressure and volume within a closed system as constant when temperature and moles remain at a fixed... An ideal gas or perfect gas is a hypothetical gas consisting of identical particles of zero volume, with no intermolecular forces, where the constituent atoms or molecules undergo perfectly elastic collisions with the walls of the container and each other and are in constant random motion. ...

$rho = frac {MP}{RT}$

where R is the universal gas constant, P is the pressure, M the molar mass, and T the absolute temperature. The gas constant (also known as the molar, universal, or ideal gas constant, usually denoted by symbol R) is a physical constant which is featured in a large number of fundamental equations in the physical sciences, such as the ideal gas law and the Nernst equation. ... Molar mass is the mass of one mole of a chemical element or chemical compound. ... Absolute zero is the lowest temperature that can be obtained in any macroscopic system. ...

This means that a gas at 300 K and 1 bar will have its density doubled by increasing the pressure to 2 bar or by reducing the temperature to 150 K. For other uses, see Kelvin (disambiguation). ... The bar (symbol bar), decibar (symbol dbar) and the millibar (symbol mbar, also mb) are units of pressure. ... The bar (symbol bar), decibar (symbol dbar) and the millibar (symbol mbar, also mb) are units of pressure. ... For other uses, see Kelvin (disambiguation). ...

Iridium is the densest known substance at standard conditions for temperature and pressure. This article is about the chemical element. ... In chemistry and other sciences, STP or standard temperature and pressure is a standard set of conditions for experimental measurements, to enable comparisons to be made between sets of data. ...

## Density of water

Temp (°C) Density (g/cm3)
100 0.9584
80 0.9718
60 0.9832
40 0.9922
30 0.9956502
25 0.9970479
22 0.9977735
20 0.9982071
15 0.9991026
10 0.9997026
4 0.9999720
0 0.9998395
−10 0.998117
−20 0.993547
−30 0.983854
The density of water in grams per cubic centimeter
at various temperatures in degrees Celsius [6]
The values below 0 °C refer to supercooled water.

Water - Density and Specific Weight Supercool redirects here. ...

## Density of air

T in °C ρ in kg/m³ (at 1 atm)
–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 1.165

For other uses, see Celsius (disambiguation). ... Standard atmosphere (symbol: atm) is a unit of pressure. ...

## Density of solutions

The density of a solution is the sum of the 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.

## 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 sealevel
Aerogel 1 − 2
Styrofoam 30 − 120 From
Cork 220 − 260 From
Water 1000 At STP
Plastics 850 − 1400 For polypropylene and PETE/PVC
The Earth 5515.3 Mean density
Copper 8960 Near room temperature
The Inner Core ~13000 As listed in Earth
Uranium 19100 Near room temperature
Iridium 22500 Near room temperature
The core of the Sun ~150000
Atomic nuclei ~3 × 1017 As listed in neutron star
Neutron star 8.4 × 1016 − 1 × 1018
Black hole 2 × 1030 Mean density inside the Schwarzschild radius of an earth-mass black hole (theoretical)

## References

1. ^ About.com: What is Density?
2. ^ Oxford Illustrated Encyclopedia: The Physical World p. 87
3. ^ Archimedes, A Gold Thief and Buoyancy - by Larry "Harris" Taylor, Ph.D.
4. ^ Vitruvius on Architecture, Book IX, paragraphs 9-12, translated into English and in the original Latin.
5. ^ The first Eureka moment, Science 305: 1219, August 2004. Fact or Fiction?: Archimedes Coined the Term "Eureka!" in the Bath, Scientific American, December 2006.
6. ^ Lide, D. R. (Ed.) (1990). CRC Handbook of Chemistry and Physics (70th Edn.). Boca Raton (FL):CRC Press.

## Books

• Fundamentals of Aerodynamics Second Edition, McGraw-Hill, John D. Anderson, Jr.
• Fundamentals of Fluid Mechanics Wiley, B.R. Munson, D.F. Young & T.H. Okishi
• Introduction to Fluid Mechanics Fourth Edition, Wiley, SI Version, R.W. Fox & A.T. McDonald
• Thermodynamics: An Engineering Approach Second Edition, McGraw-Hill, International Edition, Y.A. Cengel & M.A. Boles

This is a list of the chemical elements, sorted by density measured at standard temperature and pressure. ... Charge density is the amount of electric charge per unit volume. ... In physics, buoyancy is the upward force on an object produced by the surrounding fluid (i. ... Bulk density a property of particulate materials. ... Dord is one of the most famous errors in lexicography, a word accidentally created by the G. and C. Merriam Companys staff and included in in the sedond edition of its New International Dictionary, in which the term is defined as density. Philip Babcock Gove, an editor at Merriam... Energy density is the amount of energy stored in a given system or region of space per unit volume, or per unit mass, depending on the context. ... The expression lighter than air refers to objects, usually aircraft, that are buoyant in air because they have an average density that is less than that of air (usually because they contain gases that have a density that is lower than that of air). ... The number density, in physics, refers to the number of entities (often of particles, but it could be of sound waves, galaxies, etc. ... The specific weight of a structure or material is the weight required to carry out a particular task, e. ... Temperature and air pressure can vary from one place to another on the Earth, and can also vary in the same place with time. ... Conversion Calculator for Units of Density PICKLES Category: ... It has been suggested that Ã–chsle scale and BaumÃ© scale be merged into this article or section. ...

Results from FactBites:

 Density Altitude Calculator - English (453 words) Density altitude is defined as the altitude in the International Standard Atmosphere that has the same air density as the air being evaluated. The density of the air is reduced by decreased air pressure, increased temperatures and increased moisture. Relative density is the ratio of the actual air density to the standard sea level density, expressed as a percentage.
 Density - MSN Encarta (514 words) In physics, density is the ratio of the mass of a substance to its volume, and it can be calculated by dividing the mass by the volume. Specific gravity is the density of a substance divided by the density of another substance that is used as a standard. Particle density is the number of particles in a given volume divided by that volume.
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