Q) Which weighs more:A kilogram of feathers or a kilogram of iron?
DENSITY
What is Density?
If you take the same volume of different substances,
then they will weigh different amounts.
Wood
Water
Iron
1 cm3
1 cm3
1 cm3
0.50 g
1.00 g
8.00 g
IRON
Q) Which has the greatest mass and therefore the most dense?
Density is the Mass per unit Volume
Cube
Representations
1 m3 = 1 000 000 cm3
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 119
Density Equation:
g
Density =
Mass
Volume
g/cm3
cm3
d= m
V
d = m = 18.9g = 16.88 g/cm3
V 1.12cm3
No – it is not pure gold!
Example:
Q) A gold-colored ring has a mass of
18.9 grams and a volume of 1.12 cm3.
Is the ring pure gold? (The density of
gold is 19.3 g/ cm3.)
DENSITY OF A REGULAR SOLID
Find the Mass of the
solid on a balance.
2.0 cm
Measure the three
lengths and calculate
the Volume.
d = m = 240 =10.0 g/cm3
(i.e., V = l x w x h )
V 24
3.0 cm
(2cm * 3cm * 4cm = 24 cm3) Calculate the Density.
m = 240 g
4.0 cm
DENSITY OF AN IRREGULAR SOLID
m = 360 g
80 cm3
50 cm3
d = m = 360 =12.0 g/cm3
V 30
 Find the Mass of the solid on
a balance.
Fill the Measuring Cylinder
with Water to a known
Volume.
 Add the Object.
 Work out the Volume of
Water that is displaced.
 Calculate the Density.
What happens when you put an object in a fluid?
If the object is less dense than the fluid…
it floats
What happens when you put an object in a fluid?
If the object is more dense than the fluid…
it sinks!
What happens when you put an object in a fluid?
If the object is as dense as the fluid…
Neither floats nor
sinks!