Density

The average density of an object or substance, r, is defined to be the mass of the object divided by its  volume:

19_01

It is important to realize that the density of an object is characteristic of the  substance from which that object is made.  For example, the density of a copper statue is characteristic of copper, not of the statue itself. Therefore, if  we can determine the density of an object made of a pure substance, we can identify that substance simply by referring to a table of densities. For  example, if we determine that the average density of an object is 8,900 kg/m3, then we can conclude that the object is most likely made of copper  by referring to the table below, which gives a few densities of interest.

Material

Density (kg/m3)

Interstellar Space

1 x 10-20

Best laboratory vacuum

1 x 10-17

Air

1.21

Styrofoam

100

Ice

917

Pure Water

1,000

Sea water

1,024

Whole blood

1,060

Earth (average)

5,500

Aluminum (element, Al)

2,700

Copper (element, Cu)

8,890

Gold (element, Au)

19,300

Iron (element, Fe)

7,870

Mercury (element, Hg)

13,600

Steel

7,860

You will need to refer to this table of densities for data in solving the homework problems.