Some Fundamental Definitions In The Science of Chemistry - Some SI Units - Density

  • Posted on: 29 March 2017
  • By: Hernando Cadet
si units density

Some times or most times, we forget that the world, which is all around us, is very important, and many of us, don’t try to think about our world, from other angles.

Such angle that we should be thinking about the environment around us, is chemistry, if we are able to understand our environment, at the chemical level, then our lives would be so much simpler, and better to understand.

In today’s article we are going to continue our conversation on those, very important SI base units, which are used in chemistry.

If you want to calculate the density of an object, you would divide the mass of that object, by the volume of that object.

Therefore,

Density = mass ÷ volume.

If you decide, that you would like to isolate the volume or the mass, then you’ll need to use density, as a conversion factor.

As such, Mass = volume X density = volume X mass ÷ volume

The color code used here, is to mean that red, the volume was cancelled out, and mass was the result; after density was used as a conversion factor.

Volume = mass X 1 ÷ density = mass X volume ÷ mass

On the equation above, we did the same thing, for red, which means, that the mass cancelled out, and for green which means, that volume was the result of the equation, while using density as a conversion factor.

Density, is a characteristic property, of a substance under certain temperatures and pressures.

Also even though the value of volume and mass tend to change, Density also has a specific value, for each of its subjects.

A good example of extensive properties, are of those we mentioned earlier, such as volume and mass.

Mass and volume are good examples, of extensive properties, because they are dependent, on the amount of substance, which is present on the subject.

Intensive property, is one which is not, dependent on the amount of substance present in the subject.

Such is the case of density, which is also known as intensive property and it differs from volume and mass, for this reason.

Remember though, that for this information to be true, there has to be given a particular, or ideal, conditions of temperature and pressure.

The kilogram per cubic meter (kg/m3) is the SI unit of density; however, in chemistry, the g/L (g/dm3) or g/mL (g/cm3) units, are used as the typical unit given to density.

Below you will find a table with the common density of certain substances.

Material

Density (g/cm3)

State of Matter

hydrogen (at STP)

0.00009

gas

helium (at STP)

0.000178

gas

carbon monoxide (at STP)

0.00125

gas

nitrogen (at STP)

0.001251

gas

air (at STP)

0.001293

gas

carbon dioxide (at STP)

0.001977

gas

lithium

0.534

solid

ethanol (grain alcohol)

0.810

liquid

benzene

0.900

liquid

ice

0.920

solid

water at 20°C

0.998

liquid

water at 4°C

1.000

liquid

seawater

1.03

liquid

milk

1.03

liquid

coal

1.1-1.4

solid

blood

1.600

liquid

magnesium

1.7

solid

granite

2.6-2.7

solid

aluminum

2.7

solid

steel

7.8

solid

iron

7.8

solid

copper

8.3-9.0

solid

lead

11.3

solid

mercury

13.6

liquid

uranium

18.7

solid

gold

19.3

solid

platinum

21.4

solid

osmium

22.6

solid

iridium

22.6

solid

white dwarf star

107

solid