Density
• Density is how much mass something
has in a certain volume
100kg
200kg
How can one have more
The
Which
blueblock
blockhas
must have
matter if they are the same
more
a higher
matter density!
in it?
size?
The yellow block has more
matter contained in the
has
sameWhich
volumeblock
as the
blue
block.
the
How
doTherefore,
you
know?
higher
density?
yellow matter must be
more dense.
If it is the same
type of matter, then
it has the same
density because
the matter is
Which
block
has
equally crowded.
higher density?
The size of the
piece does not
make a difference.
The pink block is
smaller, but it still has a
Which
block
is
higher
density,
because
the
matter
is more
more
dense?
crowded.
You can use density to predict if
an object will float or sink.
If something is
more
dense
Will the
yellow
object
than
thesink?
fluid,
float or
it will sink.
If something is
lessbrown
denseblock
Will the
than
thesink?
fluid,
float or
it will float.
The duck is
less dense than water
so it floats
The anchor is
more dense than water
so it sinks
How can a balloon float just by
filling it with hot air?
video
When a fluid gets hot, its density changes!
Inside balloon
Outside balloon
How can you figure out the
density of an object?
You need to measure the
mass and the volume.
• The formula for calculating density is:
Density =
Mass
Volume
m
v
d
DMV Triangle:
Cover the variable that you need
to find, the triangle will tell you
what math to do to find it.
Remember how to measure mass?
• Mass is a measurement of the amount
of matter that something has.
• The SI unit for mass is the gram.
• Mass is measured with a balance.
Balance
Remember how to measure volume?
• Volume is the amount of space that
something takes up
Volume is measured differently for liquids and solids
Volume of Liquids
• The SI unit for liquid is liter
• Liquid volume is measured with a graduated
cylinder
Rectangular Solids
Height
3 3
1.6cm x 1.3cm x 4.1cm = 8.528
8.5 cm
cm
Length
cm
x
cm
x
cm
= cm3
Irregular Solids
Displacement method
65 mL
69 mL
Because
the hammer
is solid, we
use cm3!
Volume of Hammer? 4 mL or 4 cm3
Calculating density is simple!
1. Measure the mass.
2. Measure the volume.
3. Divide.
Density =
Mass (grams)
Volume (cm3)
The units that we use for
density are grams/cm3
Say “per”
Density Problems
(Use the DMV triangle!)
1. If 52 grams of matter has a volume of 65
cm3, what is the density of the matter?
Will it float or sink in water?
2. If a 32 gram piece of wood has a density
of 4 g/cm3, what is the volume?
3. A metal washer has a mass of 27 g/cm3
and a volume of 3 cm3. What is its
mass?
4. If an object has a mass of 810 g and a
volume of 45 cm3, what is its density?
Will it float or sink in water?
5. When you add a rock to 70 mL of water
in a graduated cylinder, the water rises to
80 mL. The density of the rock is 4.2
g/cm3. What is the rock's mass?
6. What is the volume of a sample of liquid
with a density of 20 g/cm3 and a mass of
25 g?
7. A 540g fish displaces 90 cm3 of water.
What is the density of the fish?