Density
What kind of property is density?
Chemical or Physical???
Mass per unit volume of an object
“How heavy something feels for its size”
46
Density Measurement
g/mL or g/cm3
density$of$unknown$object$
40$
17,$38$
35$
15,$34$
30$
16,$26$
Mass$(g)$
25$
20$
7.1,$20$
11,$20$
15$
10$
6.8,$6.2$
5,$6$
1,$5.9$
5$
0$
0$
2$
4$
6$
8$
10$
12$
14$
Volume$(ml)$
48
16$
18$
density$of$unknown$object$
40$
17,$38$
35$
15,$34$
30$
16,$26$
Mass$(g)$
25$
20$
7.1,$20$
11,$20$
15$
10$
6.8,$6.2$
5,$6$
1,$5.9$
5$
0$
0$
2$
4$
6$
8$
10$
12$
14$
Volume$(ml)$
49
16$
18$
Slope = (Y2-Y1) / (X2-X1)
density$of$unknown$object$
40$
17,$38$
35$
15,$34$
30$
16,$26$
Mass$(g)$
25$
20$
7.1,$20$
11,$20$
15$
10$
6.8,$6.2$
5,$6$
1,$5.9$
5$
0$
0$
2$
4$
6$
8$
10$
12$
14$
Volume$(ml)$
50
16$
18$
Measuring Volume
mL or cm3
Using Density to Identify
Material
Aluminum
Air
Gold
Density (g/mL)
2.70
0.00119
19.31
Name some Low density objects
Name some High Density objects
ž Objects
that may feel very “heavy” for their size
Density Sample Problem
A piece of iron has a mass 49.6 g
and a volume of 6.3 cm3. What
is the density of iron? (Show all
work)
Density Sample Problem
What is the density of a piece of
Styrofoam that has a mass of 27
g and a volume of 152 cm3?
Density Sample Problem
What is the density of a liquid if
a 25 mL sample has a mass of
35.1 g?
Density Sample Problem
An object has a mass of 51.3 g.
When it is placed in a graduated
cylinder with water, the water
level rises from 35 mL to 47.5
mL. What is the density of the
material?
Density Sample Problem
When a certain alloy is placed in
water, the level in a graduated
cylinder rises to 57.0 mL from
25.1 mL. What is the density of
a 48.2 g sample of the alloy?
¡
zeros at the end of a decimal count as
significant digits
Density Equation - Rearranged
ž You
have a 10 mL sample of a liquid. The liquid
is known to have a density of 0.93 g/mL. What
is the mass of your sample?
m
d=
v
¡ d=0.93g/mL
d *v = m
(0.93 has two significant digits.
The zero is a place holder.)
¡ v=10mL (10 only has one significant digit.
The zero is a place holder.)
¡ m= 9 g
Density Equation - Rearranged
ž A
bowling ball has a mass of 16,009 g and a
density of 3.12 g/cm3. What is the volume of
the bowling ball?
m
d=
v
¡ d=3.12
d *v = m
m
v=
d
g/cm3
¡ m=16,009 g (16,009 has 5 significant digits.)
¡ v= 5130 cm3
Try this one
ž A
cube with a height of 2 cm has a mass of
17g. What is the density of the cube?
¡ d=
?
¡ m= 17g
¡ v= L*W*H
¢
h = 2 cm
2cm* 2cm* 2cm = 8 cm3
¡ d=
2g/cm3
62
Try this one
A measuring cup initially holds
200 mL of water. After a cell
phone is submerged in the cup,
the volume reading is 287 mL.
What is the mass of the cell
phone if it has a density of 7.3
g/cm3.
63
Summary:
ž Design
a set of rules (or a checklist) for how
to determine the number of significant digits
in a measurement.
64
Density – Physical Property
ž Will
it float?
ž Why or Why not?
D=
0.8 g/mL
D = 1.0 g/mL
Density – Physical Property
ž Will
it float?
ž If the substance is less
dense than the
surrounding liquid, it
will float…
D=
0.8 g/mL
D = 1.0 g/mL