Video Overview
The density of an object is the mass of the object divided by the volume of the object. This
relationship can be expressed using the following word equation: d e n s i t y m a s s v o l u m e = .

For two objects that have the same volume, the object that weighs more has the greater mass
and so has the greater density.

The mass of an object can be easily measured using a balance. The mass of the object does not depend in any way on its shape.

The volume of an object can be easily measured by placing it into a measuring cylinder containing some water.

An object displaces a volume of water equal to the volume of the object.

The volume displaced by an object does not depend on the shape of the object. If a cube is
replaced by a disk with the same volume, the same volume of water is displaced.

The cube or disk could be replaced by any other object, with either a regular shape or an
irregular shape.

For a cube, the volume can also be found by measuring how long three perpendicular edges of
the cube are: the length, width, and height. If these values are known, the volume is
calculated using the following formula: volume = length × width
× height.

Irregular objects have volumes that cannot be found by simple length measurements and
formulas.

The irregular object shown above has a large number of edges, none of which are straight. The
only easy way to measure its volume is by using the water displacement method. The density of
the irregular object is its mass divided by its volume. The density is then found using the
following formula: d e n s i t y m a s s v o l u m e = .