DENSITY
There are three phases of
matter:
solid
liquid
gas
Density – how close
together the molecules are
Solids
Molecules
close
together
Liquids
Molecules
spread out
further
Gas
Molecules spread far
apart
To determine density, you
must divide the mass by
the volume.
Density =
mass
volume
Mass is measured in
grams using a triple beam
balance…
or a digital scale.
We can determine the mass of
the box using the digital scale.
750 g
Some units for mass….
• grams (g)
• kilograms (kg)
• milligrams (mg)
….and conversion factors
• 1000 g = 1 kg
• 1000 mg = 1 g
• 1 000 000 mg = 1 kg
Volume of a regularly-shaped
object can be measured using
a ruler.
Some units for volume….
• cubic centimeter (cm3)
• milliliter (mL)
• liter (L)
….and conversion factors
• 1 cm3 = 1 mL
• 1000 mL = 1 L
If the object has smooth
sides where a ruler can be
used to measure the length,
width, and height, it is
considered regular-shaped.
Volume = length x width x height
2 cm
5 cm
15 cm
V=lxwxh
V = 15 cm X 5 cm X 2 cm
V = 150
3
cm
Density =
mass
Volume
m
D
V
Density =
mass
Volume
750 g
D
150 cm3
Density =
mass
Volume
750 g
5 g/cm3 150 cm3
Determine the volume of
the cube.
3 cm
V=lxwxh
V = 3 cm X 3 cm X 3 cm
V = 27
3
cm
A piece of silver has a mass of 2800
grams and occupies a volume of 266 cm3.
What is the density of silver?
If a block of copper measures 2.00 cm x
4.00 cm x 5.00 cm and its mass is
356 grams, what is its density?
Volume of a
liquid is
measured
in mL using
a graduated
cylinder,
beaker,
or flask.
Objects that do not have
smooth sides to measure are
called irregular-shaped.
To measure the volume of
these objects we use water
displacement.
Water is put
into a
graduated
cylinder and
the volume of
the water is
measured.
50
40
30
20
10
The object is
placed in the
graduated
cylinder.
50
40
30
The volume of
the water and
the object is
determined.
20
10
The first volume is
subtracted from the second
volume.
40 mL – 29 mL = 11 mL
The volume of the object
is 11mL.
Density does not depend on the
amount of the substance (intensive
property).
The density of the block is 16 g/cm3
If it is cut in half, what
happens to the density?
Density of block is
16 g/cm3
Density of block is
16 g/cm3
Buoyancy is the upward force
of a fluid on an object.
Another example of buoyancy is
a hot air balloon. The air, a fluid,
buoys the balloon.
Some organisms use
buoyancy to move. An
example is the jellyfish.
The density of water is
1g/mL.
If an object
with a density
of less than
1g/mL is
placed in the
water, it will
float.
If an object with
a density of
greater than
1g/mL is placed
in the water, it
will sink.
The density of the
liquid determines if the
material placed in it
will float or sink.
We can make a density
column to demonstrate
the different densities of
materials.
DENSITY
Alcohol
Oil
Water
COLUMN
Can you give
an estimation
of the density
of the alcohol
and the oil?
Density = 1g/mL
DENSITY
COLUMN
Alcohol
Oil
Water
Density = 1g/mL
The density of
the oil is less
than 1 g/mL.
The density of
the alcohol is
less than the
density of the
oil.
DENSITY
COLUMN
Alcohol
Density = .75 g/mL
Oil
Density = .96 g/mL
Water
Estimate
the
density of
the piece
of wood.
The density
Density = 1g/mL of wood is
.8 g/cm3.
DENSITY
COLUMN
Alcohol
Density = .75 g/mL
Oil
Density = .96 g/mL
Water
Estimate
the
density of
the piece
of ice.
The density
Density = 1g/mLof ice is
.9 g/cm3.
Fluids can flow, but not all
fluids flow quickly.
Viscosity is defined as
the resistance to flow.
Some fluids move slowly.
They have a high viscosity.
Syrup
pours
slowly.
It is very viscous.
Glue is
also
viscous.
Some fluids move quickly.
They have a low viscosity.
Water
pours
quickly.
It is less viscous.
We can compare viscosity by putting a drop
of three different fluids on a board and then
tilting the board.
1
2
3
Fluid #1 was the least viscous. Why?
Which fluid was the most viscous?
How could you tell?
Being less viscous has its
advantages!