Density

Densityis ameasurementthat compares the amount ofmatteran object has to itsvolume.An object with much matter in a certain volume has high density. An object with little matter in the same amount of volume has a low density. Density is found by dividing themassof an object by itsvolume:

$\rho ={\frac {m}{V}}$

whereρis the density,mis the mass, andVis the volume.

Changes of density

In general, density can be changed by changing either thepressureor thetemperature.Increasing the pressure always increases the density of a material. Increasing the temperature usually lowers the density, but there are exceptions. For example, the density ofwaterincreases slightly between itsmelting pointat 0 °C and 4 °C. When water freezes, it expands by about 9% in volume, makingicethat is less dense than liquid water. Water expands as it drops below 4 °C.

Measures

Fresh water is often used as a standard ofrelative density.This is calledspecific gravity.

The most commonSIunits for density areg/cm³andkg/m³.When thenumeratoris much larger than thedenominator,that means the substance has a higher density. When the denominator is much larger than the numerator, the substance has a lower density.

Other uses of the term

"Density" sometimes means the ratio between otherpropertiesinstead of mass and volume. Then it means how much of a property can be found in a specific piece of what they are looking at. For example,population densityis how many people live within the same amount of land area. The population density in the city is higher than the country side because people live closer to each other in the city. Incomputers,storage densityis how muchdatacan fit on adata storage devicein relation to its physical size. ABlu-raydisc has a higher storage density than aDVDwhich has a higher storage density than aCD,even though they all have almost exactly the same volume.

Related pages

• Archimedes' principle