Units of mass and volume are involved in density. Therefore, units of density are a combination of these two. Since density is the mass of a unit volume of a substance, it is measured in mass units per volume units.
Examples of these density units are listed below:
Grams per cubic Centimeter – g/m3
Grams per milliliter – g/ml
Kilograms per liter – kg/l
To illustrate the use of the metric system, we can now see the relationship between these density units. Take water for example: we have already learned that 1 gram of water has a volume of 1 milliliter. We have also learned that:
1000 grams (g) = 1 kilogram (kg)
1000 milliliters (ml) = 1 liter (l)
1000 kg = 1 ton (t)
1000 l = 1 cubic meter (m3)
Therefore the density of water can be written as 1 g/ml, or 1kg/l, or 1 t/m3
ie 1 g/ml = 1 kg/l = 1 t/m3.
Examples of density.
The following densities are of substances important to coal preparation.
1 gram per cubic centimeter – 1 g/m3 or 1 g/ml
Clean Coal:
As will be explained later, the density of clean coal varies, but the following value is an example.
About 1.3 grams per cubic centimeter – 1.3 g/m3
Shale density also varies; the following is a typical value.
About 2.4 grams per cubic centimeter – 2.4 g/m3
It will be seen from the above figures that coal is more dense than water, and shale more dense than coal.