A Physical Property of Matter
Just what IS density????
 Density is the amount of matter in a given volume.
 Density = mass/volume
D = m/v
 Density is unique for every substance. Solids, liquids, &
gases ALL have unique densities.
 Does not depend
or vary with
the size of the
sample.
 Is always constant.
Which one is more dense?
 People in a square
 Which square is more dense?
Which one is more dense?
 Now which one is more dense?
Which one is more dense?
LOOK
CLOSELY.
More particles
packed into the
same space.
Density of all objects is compared
to the density of water!!
Density of water is 1.0
3
g/cm .
 If the density is greater than 1.0 g/cm3, then the object
will sink in water.
 If the density is less than 1.0 g/cm3, then the object will
float in water.
Will these objects sink or float?
Object
Density (g/cm3)
Cork
0.2-0.3
Anchor
7.8
Spruce wood oar
0.4
Apple
0.9
Orange
0.84
Orange without peel
1.16
ANSWER AS A CLASS!!
There is ALWAYS an exception!
 When you freeze water, the density of the ice is LESS
than the density of water (even though they are both
the same substance). When you freeze ice, it
crystallizes and leaves more gaps which increases the
volume (by about 9%) and therefore the density goes
down.
 THUS, ICE CAN FLOAT IN WATER!
READ AS A CLASS!!
Water vs. Ice
Air spaces between
water molecules!
CAREFUL!
 Cutting an object into pieces WILL NOT change its
density. You have not changed the particle
compaction in any way!
 Example: If the density of a piece of American red oak
wood is .74 g/cm3. If you cut the piece of would in half,
the density would NOT decrease by two, IT WOULD
STAY THE SAME!
READ AS A CLASS!!
Density Formula
 Density = mass
OR
mass ÷ volume.
volume
 Units for density: g
cm3
ALWAYS
REMEMBER
UNITS!
 Why are these the units for density?
Mass is measured in grams.
Volume is measured in cm3 or mL.
WRITE THIS
DOWN!!
REMEMBER:
Mass is how much matter is inside of an object.
Volume is how much space something takes up.
Let’s try a density problem together.
WORK OUT ON NOTE SHEET!
 Frank has a paper clip. It has a mass of 9g and a volume
of 3cm3. What is its density?
D = 9g/3cm3 = 3 g/cm3
 Frank also has an eraser. It has a mass of 3g, and a
volume of 1cm3. What is its density?
D = 3g/1cm3 = 3 g/cm3
Take 5 minutes to complete!!
Work on these problems with your neighbor.
 Jack has a rock. The rock has a mass of 6g and a
volume of 3cm3. What is the density of the rock?
D = 6g/3cm3 = 2 g/cm3
 Jill has a gel pen. The gel pen has a mass of 8g and a
volume of 2cm3. What is the density of the pen?
D = 8g/2cm3 = 4 g/cm3
WORK OUT ON NOTE SHEET!
Now, try these on your own.
 Allicia has a watch. It has a mass of 4g and a volume of
2cm3. What is the density of the watch?
D = 4g/2cm3 = 2 g/cm3
 Mia has a wallet. It has a mass of 15g and a volume of
5cm3. What is the density of the wallet?
D = 15g/5cm3 = 3 g/cm3
WORK OUT ON NOTE SHEET!
Water Displacement Method
If you have an irregular shaped object
you will use the water displacement
method to find its volume.
You will use the triple beam balance
to find it’s mass. Then you will
calculate the object’s density.
What is the volume of the
dinosaur????
Volume = 0.8 mL
Initial volume = 4.8 mL
Final Volume = 5.6 mL
5.6 - 4.8 = 0.8 mL
Initial
Water Level
Final
Water Level
Liquid Layers
 If you pour together liquids that don’t
mix and have different densities, they
will form liquid layers.
 The liquid with the highest density
will be on the bottom.
 The liquid with the lowest density will
be on the top.
Liquid Layers – Try with your neighbor
 Which liquid has the
highest density?
 Which liquid has the
lowest density?
 Which liquid has the
middle density?
ANSWER ON NOTE SHEET!
ANSWERS ON NEXT SLIDE!
Liquid Layers – Answers!!
 Which liquid has the
highest density?
golden syrup
 Which liquid has the
lowest density? oil
 Which liquid has the
middle density? water
Complete orally as a class.
Liquid Layers – Try on your own!
 Imagine that the
liquids on the right
have the following
densities:
 15g/cm3
 3g/cm3
 7g/cm3
10g/cm3
9g/cm3
12g/cm3
 Match the colors to the
correct densities.
3g/cm3
7g/cm3
9g/cm3
10g/cm3
12g/cm3
15g/cm3
STOP HERE!!!!
Liquid Layers
Complete orally as a class.
 Check out this picture. Which
layer has the highest density? Green
 Which layer has the lowest
density? Yellow
 Imagine that the liquids have the
3 g/cm3
following densities:
 10
g/cm3.
 6g /cm3.
g/cm3.
3
5 g/cm3.
 Which number would go with
which layer?
5 g/cm3
6 g/cm3
10 g/cm3
On your own…
 Your friends at your lunch table all have different stuff
in their lunch. Liquid A has a density of 1.07 g/ml,
Liquid B has a density of 0.98 g/ml, Solid C has a
density of 1.12 g/cm3, and Mush D has a density of 1
g/cm3. You decide to make a gross combination of the
four in your water bottle. Which order will they appear
in, from bottom to top?
 a) Solid C, Mush D, Liquid A, and Liquid B on top?
 b) Solid C, Mush D, Liquid B, and Liquid A on top?
 c) Solid C, Liquid A, Mush D, and Liquid B on top?
 c) Liquid A, Liquid B, Solid C, and Mush D on top?
Review
 What is the formula for density?
 What happens if you pour together liquids that have
different densities?
 Will the liquid on the top have the highest or lowest
density?
 Will the liquid on the bottom have the highest or
lowest density?
Super Scientist Question of the Day
 Jake has a book, a ruler, and a balance.
 How can Jake find the density of the book with
the tools he has?
Density of Coke