
:''For other senses of "density", see density (disambiguation).'' Density (symbol: ''ρ'' - Greek language: rho) is a measure of mass per unit of volume. The higher an object's density, the higher its mass per volume. The ''average density'' of an object equals its total mass division (mathematics) by its total volume. A denser object (such as iron) will have less volume than an equal mass of some less dense substance (such as water). The SI unit of density is the kilogram per cubic metre (kilogram/cubic metre) : where :''ρ'' is the object's density (measured in kilograms per cubic metre) :''m'' is the object's total mass (measured in kilograms) :''V'' is the object's total volume (measured in cubic metres) ==Various types of density== Under specified conditions of temperature and pressure, density of a fluid is defined as described above. However, the density of a solid material can be different, depending on exactly how it is defined. Take sand for example. If you gently fill a container with sand, and divide the mass of sand by the container volume you get a value termed ''loose bulk density''. If you took this same container and tapped on it repeatedly, allowing the sand to settle and pack together, and then calculate the results, you get a value termed ''tapped'' or ''packed bulk density''. Tapped bulk density is always greater than or equal to loose bulk density. In both types of bulk density, some of the volume is taken up by the spaces between the grains of sand. If you are interested in the density of the grain of sand itself you need to measure either ''envelope density'' or ''absolute density''. ==Other units== Density in terms of the SI base units is expressed in terms of kilograms per cubic metre (kg/m³). Other units fully within the SI include grams per cubic centimetre (g/cm³) and megagrams per cubic metre (Mg/m³). Since both the litre and the tonne or metric ton are also acceptable for use with the SI, a wide variety of units such as kilograms per litre (kg/L) are also used. Imperial units or US customary units, the units of density include pounds per cubic foot (lb/ft³), pounds per cubic yard (lb/yd³), pounds per cubic inch (lb/in³), ounces per cubic inch (oz/in³), pounds per gallon (for U.S. or imperial gallons) (lb/gal), pounds per U.S. bushel (lb/bu), in some engineering calculations slug (mass) per cubic foot, and other less common units. The maximum density of pure water at a pressure of one standard Atmosphere (unit) is 999.972 kg/m³; this occurs at a temperature of about 3.98 °C (277.13 K). From 1901 to 1964, a litre was defined as exactly the volume of 1 kg of water at maximum density, and the maximum density of pure water was 1.000 000 kg/L (now 0.999 972 kg/L). However, while that definition of the litre was in effect, just as it is now, the maximum density of pure water was 0.999 972 kg/dm3. During that period students had to learn the esoteric fact that a cubic centimetre and a millilitre were slightly different volumes, with 1 mL = 1.000 028 cm3. (often stated as 1.000 027 cm3 in earlier literature). ==Measurement of density== A common device for measuring fluid density is a pycnometer. A device for measuring absolute density of a solid is a gas pycnometer. ==Density of substances== Perhaps the highest density known is reached in neutron star matter (see neutronium). The gravitational singularity at the centre of a black hole, according to general relativity, does not have any volume, so its density is undefined. The densest naturally occurring substance on Earth is Iridium, at about is 22,650 kg/m3. A table of densities of various substances:
See also Gas_constant#Density_of_gas
Note the low density of aluminium compared to most other metals. For this reason, aircraft are made of aluminium. Also note that air has a nonzero, albeit small, density. Aerogel is the world's lightest solid.
'''Table - density of air ''ρ'', Speed of sound in air ''c'',
acoustic impedance ''Z'' vs. temperature °C {| border=\"1\" cellpadding=\"1\" cellspacing=\"0\" |colspan=\"4\" align=\"center\" | Impact of temperature ''' |- |'''' in °C|| ''c'' in m/s || ''ρ'' in kg/m³|| ''Z'' in N·s/m3 |- | - 10 || 325.4 || 1.341 || 436.5 |- | - 5 || 328.5 || 1.316 || 432.4 |- | 0 || 331.5 || 1.293 || 428.3 |- | + 5 || 334.5 || 1.269 || 424.5 |- | + 10 || 337.5 || 1.247 || 420.7 |- | + 15 || 340.5 || 1.225 || 417.0 |- | + 20 || 343.4 || 1.204 || 413.5 |- | + 25 || 346.3 || 1.184 || 410.0 |- | + 30 || 349.2 || 1.164 || 406.6 |} ==See also== *ISO 31: volumic mass *Dord *Standard temperature and pressure *Relative density (specific gravity) Continuum mechanics Introductory physics lv:Blīvums ms:Ketumpatan
Water isn't really defined to have density 1 is it? That's a schoolboy definition. --User:drj Mayhaps, I certainly was a schoolboy once :-) The fact that one litre of water weighs exactly one kilogram os no accident however. The SI units were chosen carefully, although i know not if the metre or the kilogram was defined first (my money is on the metre), the relation between them is indeed found through the density of water (at 4 degrees celsius if memory serves correctly). --Anders Törlind. Oh, by the way, is the kilogram still defined as the lump of platinum they hold in Paris, or is it defined as a certain number of atoms of something? --Anders Törlind I wondered about this recently. My research confirms what :kilogram says. There is a standard mass made from platinum/rhodium. I guess it is too difficult to define it as the number of atoms of something. --User:drj ---- I believe that the metere was originally defined to be 1x10-6 of the distance from the equator to the north pole via a line that went through :Paris, this was mesured incorrectly at the time, so the distance is somewhat different. The other units as far as I know are based on that. The kilogram was originally based on a cubic decimeter of water, but that is much too variable to be used as a reference.-- User:mike dill :Actually, one ten-millionth, which is 10-7. (I fixed your tags.) user:Vicki Rosenzweig ---- Do you have the reference for the platinum density of 21.09? According to http://hypertextbook.com/facts/2004/OliviaTai.shtml, the density is 21.45 and they list 5 references. When I Google platinum density, the first entry webelements.com (another wiki) agrees with 21.09, but going on down the list several pages, everyone else says from 21.4 to 21.5. If you change to 21.45 then change the Wikipedia platinum article also. User:Art LaPella 05:04, Aug 22, 2004 (UTC) I have checked the CRC Handbook of Chemistry and Physics (60th edition, page B-106) and it gives 21.45 at 20 degC: so have changed here and on the platinum page. --User:GPoss 06:36, Aug 22, 2004 (UTC) == Osmium vs Iridium == It seems the articles for Osmium and Iridium give different values for the density of Osmium compared to the value in the density table, affecting the order of the elements in the table. Apparently Osmium should be listed at 22661 kg/m³ rather than 22610 kg/m³. --User:Vinsci 14:48, 4 Apr 2005 (UTC)
See other meanings of words starting from letter:
Words begining with Density:
Density
Density
Density-functional_theory
Density_(disambiguation)
Density_21.5
Density_altitude
Density_estimation
Density_function
Density_Functional_Theory
Density_functional_theory
Density_functional_theory
Density_functional_theory/to_do
Density_matrix
Density_Matrix_Renormalization_Group
Density_matrix_renormalization_group
Density_of_air
Density_of_air
Density_of_states
Density_operator
Density_state
Density_state
Density
:''For other senses of "density", see density (disambiguation).'' Density (symbol: ''ρ'' - Greek language: rho) is a measure of mass per unit of volume. The higher an object's density, the higher its mass per volume. The ''average density'' of an object equals its total mass division (mathematics) by its total volume. A denser object (such as iron) will have less volume than an equal mass of some less dense substance (such as water). The SI unit of density is the kilogram per cubic metre (kilogram/cubic metre) : where :''ρ'' is the object's density (measured in kilograms per cubic metre) :''m'' is the object's total mass (measured in kilograms) :''V'' is the object's total volume (measured in cubic metres) ==Various types of density== Under specified conditions of temperature and pressure, density of a fluid is defined as described above. However, the density of a solid material can be different, depending on exactly how it is defined. Take sand for example. If you gently fill a container with sand, and divide the mass of sand by the container volume you get a value termed ''loose bulk density''. If you took this same container and tapped on it repeatedly, allowing the sand to settle and pack together, and then calculate the results, you get a value termed ''tapped'' or ''packed bulk density''. Tapped bulk density is always greater than or equal to loose bulk density. In both types of bulk density, some of the volume is taken up by the spaces between the grains of sand. If you are interested in the density of the grain of sand itself you need to measure either ''envelope density'' or ''absolute density''. ==Other units== Density in terms of the SI base units is expressed in terms of kilograms per cubic metre (kg/m³). Other units fully within the SI include grams per cubic centimetre (g/cm³) and megagrams per cubic metre (Mg/m³). Since both the litre and the tonne or metric ton are also acceptable for use with the SI, a wide variety of units such as kilograms per litre (kg/L) are also used. Imperial units or US customary units, the units of density include pounds per cubic foot (lb/ft³), pounds per cubic yard (lb/yd³), pounds per cubic inch (lb/in³), ounces per cubic inch (oz/in³), pounds per gallon (for U.S. or imperial gallons) (lb/gal), pounds per U.S. bushel (lb/bu), in some engineering calculations slug (mass) per cubic foot, and other less common units. The maximum density of pure water at a pressure of one standard Atmosphere (unit) is 999.972 kg/m³; this occurs at a temperature of about 3.98 °C (277.13 K). From 1901 to 1964, a litre was defined as exactly the volume of 1 kg of water at maximum density, and the maximum density of pure water was 1.000 000 kg/L (now 0.999 972 kg/L). However, while that definition of the litre was in effect, just as it is now, the maximum density of pure water was 0.999 972 kg/dm3. During that period students had to learn the esoteric fact that a cubic centimetre and a millilitre were slightly different volumes, with 1 mL = 1.000 028 cm3. (often stated as 1.000 027 cm3 in earlier literature). ==Measurement of density== A common device for measuring fluid density is a pycnometer. A device for measuring absolute density of a solid is a gas pycnometer. ==Density of substances== Perhaps the highest density known is reached in neutron star matter (see neutronium). The gravitational singularity at the centre of a black hole, according to general relativity, does not have any volume, so its density is undefined. The densest naturally occurring substance on Earth is Iridium, at about is 22,650 kg/m3. A table of densities of various substances:
| Substance | Density in kg/m3 |
| Iridium | 22,650 |
| Osmium | 22,610 |
| Platinum | 21,450 |
| Gold | 19,300 |
| Uranium | 19,050 |
| Mercury (element) | 13,580 |
| Palladium | 12,023 |
| Lead | 11,340 |
| Silver | 10,490 |
| Copper | 8,920 |
| Iron | 7,870 |
| Tin | 7,310 |
| Titanium | 4,507 |
| Diamond | 3,500 |
| Aluminium | 2,700 |
| Magnesium | 1,740 |
| Seawater | 1,025 |
| Water | 1,000 |
| Ethyl alcohol | 790 |
| Gasoline | 730 |
| Aerogel | 3 |
| any gas | 0.0446 times the average molecular mass, hence between 0.09 and ca. 10 (at standard temperature and pressure) |
| For example air | 1.2 |
acoustic impedance ''Z'' vs. temperature °C {| border=\"1\" cellpadding=\"1\" cellspacing=\"0\" |colspan=\"4\" align=\"center\" | Impact of temperature ''' |- |'''' in °C|| ''c'' in m/s || ''ρ'' in kg/m³|| ''Z'' in N·s/m3 |- | - 10 || 325.4 || 1.341 || 436.5 |- | - 5 || 328.5 || 1.316 || 432.4 |- | 0 || 331.5 || 1.293 || 428.3 |- | + 5 || 334.5 || 1.269 || 424.5 |- | + 10 || 337.5 || 1.247 || 420.7 |- | + 15 || 340.5 || 1.225 || 417.0 |- | + 20 || 343.4 || 1.204 || 413.5 |- | + 25 || 346.3 || 1.184 || 410.0 |- | + 30 || 349.2 || 1.164 || 406.6 |} ==See also== *ISO 31: volumic mass *Dord *Standard temperature and pressure *Relative density (specific gravity) Continuum mechanics Introductory physics lv:Blīvums ms:Ketumpatan
Density
Water isn't really defined to have density 1 is it? That's a schoolboy definition. --User:drj Mayhaps, I certainly was a schoolboy once :-) The fact that one litre of water weighs exactly one kilogram os no accident however. The SI units were chosen carefully, although i know not if the metre or the kilogram was defined first (my money is on the metre), the relation between them is indeed found through the density of water (at 4 degrees celsius if memory serves correctly). --Anders Törlind. Oh, by the way, is the kilogram still defined as the lump of platinum they hold in Paris, or is it defined as a certain number of atoms of something? --Anders Törlind I wondered about this recently. My research confirms what :kilogram says. There is a standard mass made from platinum/rhodium. I guess it is too difficult to define it as the number of atoms of something. --User:drj ---- I believe that the metere was originally defined to be 1x10-6 of the distance from the equator to the north pole via a line that went through :Paris, this was mesured incorrectly at the time, so the distance is somewhat different. The other units as far as I know are based on that. The kilogram was originally based on a cubic decimeter of water, but that is much too variable to be used as a reference.-- User:mike dill :Actually, one ten-millionth, which is 10-7. (I fixed your tags.) user:Vicki Rosenzweig ---- Do you have the reference for the platinum density of 21.09? According to http://hypertextbook.com/facts/2004/OliviaTai.shtml, the density is 21.45 and they list 5 references. When I Google platinum density, the first entry webelements.com (another wiki) agrees with 21.09, but going on down the list several pages, everyone else says from 21.4 to 21.5. If you change to 21.45 then change the Wikipedia platinum article also. User:Art LaPella 05:04, Aug 22, 2004 (UTC) I have checked the CRC Handbook of Chemistry and Physics (60th edition, page B-106) and it gives 21.45 at 20 degC: so have changed here and on the platinum page. --User:GPoss 06:36, Aug 22, 2004 (UTC) == Osmium vs Iridium == It seems the articles for Osmium and Iridium give different values for the density of Osmium compared to the value in the density table, affecting the order of the elements in the table. Apparently Osmium should be listed at 22661 kg/m³ rather than 22610 kg/m³. --User:Vinsci 14:48, 4 Apr 2005 (UTC)
See other meanings of words starting from letter:
D
DA | DB | DC | DE | DF | DG | DH | DI | DJ | DK | DL | DM | DN | DO | DP | DR | DS | DT | DU | DW | DX | DY | DZ |Words begining with Density:
Density
Density
Density-functional_theory
Density_(disambiguation)
Density_21.5
Density_altitude
Density_estimation
Density_function
Density_Functional_Theory
Density_functional_theory
Density_functional_theory
Density_functional_theory/to_do
Density_matrix
Density_Matrix_Renormalization_Group
Density_matrix_renormalization_group
Density_of_air
Density_of_air
Density_of_states
Density_operator
Density_state
Density_state
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