DENSITY

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DENSITY
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DENSITY
matter
-Mass is the amount of ________ in an object.
-Possible units
g, mg, cg, hg, dkg, kg, etc.
space
matter
-Volume is the amount of ________ that _________
occupies.
cm3, mL, km3, L, kL, etc.
-Possible units
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-Lets make a model of mass and volume in a
football bleacher scenario.
-How can we increase how tightly packed the
bleachers are?
IU!
Add more fans
Or use only half the bleachers
-The mass will be represented by the fans
-The volume will be represented by the bleachers
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DEFINITION
-The measurement of mass contained within a
specific volume is called
density
g/cm3, g/mL, mg/km3, kg/L, mg/kL, etc.
-Possible units
(Basically any unit of mass per unit of volume)
-Density can also be thought of as how tightly
packed the atoms of the substance are.
volume
-Change in either the _______ or the __________
will cause a change in the density.
mass
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-Example A Ping-Pong ball and a Golf ball have
about the same ___________ but different
_________ and therefore have different densities.
volume
masses
-The formula for density is
mass
-----------
Density
volume
-Ex. What is the density of an object that has a
mass of 50 g and a volume of 25 mL?
50g

-------
g/mL
2
25 mL
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-Since there are only three variables in the
equation, you can use the formula triangle to
solve for any of the variables
M
x
V
D
(To use the triangle simply cover up the variable
you are trying to solve for and you will see the
formula you need)
-Ex. A boomerang has a density of 0.5 g/cm3 and a
mass of 15 g, what is its volume?
15g
M
---------
30
cm3
-------


V
0.5 g/cm3
D
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-Why do the units cancel?
-Units work the same way numbers do. Look below.
2
2
3
3
3
--------
----
3
----
x
----
----

2


x

2
1
2
2
1
----
3
3
g
g
--------
5

---------

---------
cm3

3
g/cm3
g
----
----
5
cm3
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-Density and Graphs
-Since density is a ratio between two
measurements (Mass and Volume) it can easily be
plotted on a graph.
150
140
130
120
110
Mass (g)
100
90
80
70
60
50
40
30
20
10
0
35
45
10
25
30
40
50
15
20
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Volume (cm3)
-After plotting all the data for Aluminum we can
see that a _________________ was formed.
straight line
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-This shows that the density for Aluminum is a
__________, meaning that it is the same no matter
what the mass or volume.
constant
-This is actually true for all types of matter.
Examples
mass
-----------
Density
volume
13.5 g
---------
2.7
g/cm3

5 cm3
27.0 g

---------
2.7
g/cm3
10 cm3
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-Density and liquids
sink
-If an object is denser then the liquid it is in
it will ______
float
-If an object is less dense then the liquid it is
in it will ______