s8pe-10401-ca
12/8/05
9:00 PM
MAZER
Page 107
Comparing Densities
The table lists densities of some common substances. At
any given temperature, the density of a substance remains
constant. For this reason, scientists can use density to
identify particular substances.
Note that the density of a substance does not depend on
the amount of the substance that you have. Suppose you
have a sheet of thick aluminum foil. You calculate the density
as 2.7 g/cm3. You cut the aluminum foil equally into three
smaller sheets. Each sheet has a third the volume but also
has a third the mass. The density, which depends on both
the volume and the mass, does not change. The density of
each of the smaller sheets of aluminum foil is still 2.7 g/cm3.
No matter how you divide the aluminum foil, a smaller
sheet will have the same density as the original sheet.
Aerogel, shown here floating on soap
bubbles, is about 330 times less dense than
water and only 2.5 times denser than air.
CRITICAL THINKING
1. Describe a way to measure
mass and a way to measure
volume. (8.8.a)
4. Infer A metal fork has a
density of 7.8 g/cm3. Is this
fork made of aluminum?
Explain your answer.
3. An object is made of a single
substance. How can knowing
the density of the object help
you identify what the object
is made of? (8.8.a)
Substance
Density (g/cm3)
Mercury
13.60
Lead
11.34
Aluminum
2.70
Bone
1.85
Milk (whole)
1.03
Seawater
1.03
Water
1.00
Ice
0.92
Gasoline
0.73
Cork
0.24
Mercury is 13.6 times denser than water.
KEY CONCEPTS
2. How are mass and volume
related to density? (8.8.a)
Densities of Common Substances
5. Calculate A glass marble
has a volume of 5 cm3 and
a mass of 13 g. What is the
density of the marble?
CHALLENGE
6. Analyze You have a bucket
half full of ice. You find that the
ice has a density of 0.92 g/cm3.
You fill the bucket completely
with ice. What will happen to
the density of the ice? What will
happen to the density of the
substance when the ice melts?
Chapter 4: Density and Buoyancy 107
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