s8pe-104ci-ca
12/8/05
9:07 PM
MAZER
Page 109
Content Standard
8.8.b Students know how to calculate the density of substances (regular and irregular
solids and liquids) from measurements of mass and volume.
For rectangular
objects, use metric
units for measuring
the length, width,
and height. Record
the measurements
in your data table.
step 5
Write
Conclude
It Up
1. IDENTIFY LIMITS Which sources of error
might have affected your measurements?
2. APPLY How would the density of a
wet sponge compare to the density of a
dry sponge?
For irregular objects, fill
the graduated cylinder
about half full with
water. Record the
step 6
exact volume of
water in the cylinder. Note: The surface of the liquid
will be curved in the
graduated cylinder.
Read the volume of the
liquid at the bottom of the
curve, called the meniscus.
3. APPLY If someone wanted to know
the density of cardboard, would you give the
person your results for the tissue box?
Why or why not?
INVESTIGATE Further
CHALLENGE A tablespoon of salt contains
Carefully place the object you are measuring
into the cylinder. The object must be completely
under the water. Record the exact volume of
water in the cylinder containing the object by
reading the meniscus.
For each object, conduct three trials for measuring volume. Average the trials to find a final volume measurement.
Observe and Analyze
Investigation Standard
8.9.f Apply simple mathematic relationships to determine a missing quantity in a mathematic expression, given the two remaining terms (including speed = distance/time,
density = mass/volume, force = pressure p area, volume = area p height).
Write
It Up
1. RECORD OBSERVATIONS Make sure
you have filled out your data table completely.
2. ANALYZE Using the average mass and
average volume for each object, calculate the
average density of each object. Record your
densities in a table.
3. INTERPRET For each object,
explain why you chose the particular
method for measuring the volume.
both salt and air. How might you find the density
of salt alone? Note that the volume of the salt
alone cannot be found by displacing water
because salt dissolves in water.
Density
nalyze
Observe and A
ts
of Various Objec
Table 1. Masses
Object
Mass (g)
Trial 2
Trial 1
Average
rock
5 pennies
ts
of Various Objec
Table 2. Volumes
Object
3
)
lume (cm or mL
Method Used Vo
Average
3
al
Tri
2
al
Tri
Trial 1
rock
5 pennies
ects
s of Various Obj
Table 3. Densitie
Avg. Mass
Object
(g)
4. INFER Which objects were the
least dense? What did these objects
have in common?
Trial 3
Avg. Volume
3
(cm )
Density
3
(g/cm )
rock
5 pennies
Chapter 4: Density and Buoyancy 109
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