
Density is defined as the mass in a unit of
volume.

In the SI unit system, mass is measured in kg
and volume is measured in m3, thus, the unit
of density is kg/m3 (kilogram per cubic
meter). But this is inconvenient for most
substances, therefore, g/cm3 (gram per cubic
centimeter) is a more common unit of
density.
 Density
is a
characteristic
property of
matter. We can
differentiate
substances by
using their
densities.
How to
manipulate the
formula
In order to calculate the density of an object,
first we measure its mass with a scale, then
we find its volume by measuring it with a
ruler, if it has a regular shape. Otherwise we
use the graduated cylinder method for
irregular objects, and liquids. Then, by
dividing mass by volume, we find the density
of the object.
What is the volume of 24 tons of
cement? (dcement = 3000 kg/m3)
Calculate the mass of copper
having the same volume as 31,5 g
of silver. Use Table 1.7.
A bottle has a mass of 70 g when it
is empty, 90 g when it is full of
water and 96 g when it is full of a
liquid. What is the density of the
liquid in g/cm3 and kg/m3 ?
Calculate the mass of air (at 0° C)
in a room having dimensions of 3
m, 6 m, 5 m. See Table 1.7.

The density of a mixture is found by dividing
the total mass of the mixture by its total
volume.
1.3 kg of a liquid and 2 kg of
water are mixed in a container.
Find the density of the mixture.
Take dliquid = 1.3 g/cm3 and dwater
= 1 g/cm3.
Two different substances of
volumes 200 cm3 and 300 cm3 are
mixed to make an alloy. If their
densities are 1.2 g/cm3 and 1.6
g/cm3 respectively, find the
density of the alloy.
One complete rotation of earth
around its axis is called one day. It
is equal to 24 hours (h), 1 hour is
60 minutes (min) and 1 minute is
60 seconds (s). The unit of time is
the second. A stopwatch or clock
is used to measure time.
What is the equivalent of one week
in terms of hours, minutes and
seconds?