Science 7
Notes 6
How do you measure the
density of an object?
Density
Mass
Volume
If you have the density
of an object, how do you
find its mass or volume?
What does mass
measure? (see
notes 5 for
definition)
These two boxes have the same mass, how do we know?
Is it possible for
two objects that
are different in
size to the same
mass?
Explain.
What does
density measure?
What two
measurements do
you need to have
to determine the
density of the
object?
What is the
formula for
density?
Do these boxes have the same density?
Measuring Density:
In order to measure the density of an object, you need to know two
things:
 The object’s mass (how much “stuff” is in it)
 The object’s volume (how much space it takes up)
Divide the mass by the volume to get density
M
D
V
or
D = M/V
*Units for density are g/cm3
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Science 7
Another Practice
Problem:
A wood block
has a mass of 30
grams and a
volume of 15
cm3. Calculate
the density of the
ball.
Notes 6
Example 1:
A rock has a volume of 80 cm3 and a mass of 240 grams. What is
its density?
Example 2:
A fluid has a volume of 100 ml and a mass of 60 grams. What is
its density?
Another Practice
Problem:
A liquid mixture
has a volume of
42ml and a mass
of 69 grams.
Calculate the
density of the
mixture.
Remember 1 ml = 1 cm3
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Science 7
Notes 6
Using the “Badge” to Find Mass or Volume:
What is the
formula you
would use to find
the mass of an
object given the
density and
volume?
The “badge” makes it easier to find mass or volume.
What is the
formula you
would use to find
the volume of an
object given the
density and
mass?
Formulas you can derive from the badge:
Practice Problem:
Find the mass of
a block if its
density is 2g/cm3
and its volume is
20cm3.
M
D
V
D=M/V
V=M/D
M=DxV
Example 3 (finding mass):
If an object has a density of 2.5g/cm3 and a volume of 60cm3, what
is its mass?
Another Practice
Problem:
What is the mass
of a liquid if its
density is
1.5g/cm3 and is
volume is 50ml?
Practice Problem:
If an object has a
density of 3g/cm3
and a mass of 60
grams, what is its
volume?
Example 4 (finding volume):
If an object has a density of 1.5g/cm3 and a mass of 120 gram,
what is its volume?
Practice Problem:
If a liquid has a
volume of 150ml
and a density of
5g/cm3, what is
its volume?
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