DENSITY
Density of many samples is measured in labs for example in unites states oil and gas industry, they define density in general way as 'weight per unit volume' although 'weight per unit volume' is not density it is 'Specific Weight' so density is 'mass per unit volume'. Density is also known as "Volumetric Mass Density". Generally different materials have different density. Chemical element Osmium (Os having atomic number 76) is naturally occurring densest element. To simplify the comparison of densities of different materials or liquids it is needed to replace density with "relative density" as relative density is dimensionless quantity. Relative Density is also called "Specific Gravity". Specific gravity or relative density is the ratio of density of sample material to the density of standard material. Generally water is taken as standard material. If we take water as standard material than if we get relative density of a material is less than '1' means that material floats in water. Water has highest density at 4 °C i.e. 1000Kg/m3.
Density of material depends on the temperature and pressure. Effect of temperature and pressure is very less on solid and liquid but effect of temperature and pressure is very high on gases. If we increase pressure on given material than its volume get decrease that result in increase in density, similarly If we decrease pressure on given material than its volume get increase that result in decrease in density. And in case of temperature, if we increase temperature on given material than its volume get increase that result in decrease in density, similarly if we decrease temperature on given material than its volume get decrease that result in increase in density. But their are some exceptions which do not follow these rules, one of them is water means when temperature of water decreases than it makes solid ice which float on liquid water as ice have less density than liquid water i.e. Density of ice is 916.7 Kg/m3 at 0 °C, and water has a density of 999.8 Kg/m³ at 0 °C.
Definition of Density
Density of a material is defined as its mass per unit volume.
Symbol of Density
Symbol of density is 'ρ' or 'D' and pronounces as 'rho'.
Formula of Density
Density = Mass/Volume
or,
ρ = m/V
where,
ρ is density, m is mass and V is volume.
- When numerator (mass) is much larger than denominator (volume) in density formula, that shows the given substance has higher density, but when denominator (volume) is much larger than the numerator (mass), that shows the given substance has lower density.
SI Unit of Density
SI Unit of Density is Kg/m3 or g/cm3
Instruments used to measure Density
Hydrometer and Thermometer is used to measure the density of liquids.
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Hydrometer |
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Hydrometer dip in mineral oil and engine oil to measure the Density of these samples |
Density Chart |
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Material
|
Density (Kg/m3)
|
Remark
|
Air
|
1.2
|
At sea level
|
Milk
|
1027 to 1033
|
At 20 oC
|
Honey
|
1420
|
At 20 oC
|
Coconut Oil
|
925
|
At 15 oC
|
Cotton Seed Oil
|
926
|
At 16 oC
|
Olive Oil
|
918
|
At 15 oC
|
Sunflower Oil
|
919
|
At 20 oC
|
Rice Bran Oil
|
918
|
At 20 oC
|
Groundnut Oil
|
913
|
At 20 oC
|
Liquid Hydrogen
|
70
|
At about -255 oC
|
Ice
|
916.7
|
At 0 oC
|
Fresh Water
|
1000
|
At 4 oC
|
Plastics
|
1175
|
Approx for PVC
|
Glycerol
|
1261
|
Also called Glycerine or Glycerin
|
Aluminium
|
2700
|
Chief ore of Aluminium is Bauxite
|
Diamond
|
3500
|
Precious stone
|
Zinc
|
7000
|
Zinc
is found in cells throughout the body.
|
Iron
|
7870
|
Used since ancient times
|
Cobalt
|
8900
|
Found
in the Earth's crust only in chemically combined form
|
Nickel
|
8900
|
Silvery-white lustrous metal
|
copper
|
8940
|
Very high thermal and electrical
conductivity
|
Silver
|
10500
|
Highest electrical conductivity, thermal
conductivity
|
Lead
|
11340
|
Soft, malleable, and heavy metal
|
Mercury
|
13546
|
Only metallic element that is
liquid at room temperature
|
Uranium
|
18800
|
weakly radioactive because all its
isotopes are unstable
|
Iridium
|
22420
|
Densest naturally occurring element
|
Osmium
|
22570
|
Densest naturally occurring element
|
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