Densities
Introduction:
Matter has mass and occupies space. For a given homogeneous
quantity of matter, the ratio of these properties has a specific value
known as density. Density is the ratio of the mass to the volume:
Density =
mass
volume
If the mass is measured in grams and the volume in cubic
centimeters, the density has units of g/cm3 . The table below lists the
densities of some common metals.
Densities of Common Metals
Metal
Density in g/cm3
Metal
Density in g/cm3
Magnesium
1.74
Iron
7.85
Aluminum
2.70
Nickel
8.60
Zinc
7.04
Copper
8.93
Tin
7.30
Lead
11.34
Experimental:
A. Density of a metal cylinder.
Obtain a metal cylinder and record the identification number
stamped in the metal. Determine the mass to 0.001 grams. Next,
determine the volume of the cylinder by the following two methods:
(1) Volume by water displacement. Partially fill a 100 mL
graduated cylinder and record the volume. Tilt the graduated cylinder
and carefully slide the metal cylinder down into the water. The water in
the graduated cylinder must cover the metal cylinder completely. Read
and record the new water level. The volume of the metal cylinder is found
by subtracting the initial water level from the final water level.
2
(2) Volume by measurement. Measure the height and diameter of
the metal cylinder (in cm) using a metric ruler. Calculate the volume (in
cm3) by using the equation: V   r 2h   ( diameter
)2 height
2
Using these separate values for the volume (remember that 1 mL =
1
= 1cc), calculate the density for the metal cylinder. Don’t be
surprised if the two density calculations are a bit off.
cm3
B. Density of a Salt Solution.
By adding various volumes of a salt solution to a 10 mL graduated
cylinder and carefully measuring the volume and total weight, a straightline graph can be made. The density of the salt solution can be
determined from the graph. Plot the weight of the 10 mL graduated
cylinder and salt solution on the vertical axis and the volume of the salt
solution on the horizontal axis. Draw the best straight line through the
points.
The slope of the line is the density of the salt solution. To
determine the slope, choose two points on the line some distance apart.
Each of these points has two values; one for the x-axis x1, x2; one for the
y-axis, y1, y2. The slope is found by the equation:
slope 
rise y2  y1

 density
run x 2  x1
Weigh a 10 mL graduated cylinder containing approximately 2 mL,
5 mL, 7 mL, and 10 mL of salt solution. Record the data in a similar
manner to the example shown below:
Data
Volume of Salt Solution in mL
Weight of graduated cylinder and solution in grams
1.95
32.85
5.16
36.15
7.50
38.52
9.23
41.05
Using your data plot a graph with the weight of the graduated
cylinder and solution on the vertical axis and the volume of solution on
the horizontal axis. Mark each point with a bold dot. Draw the best
straight line through the points. Clean and dry the graduated cylinder
and record the weight of the empty graduated cylinder from the balance
(for comparison).
3
Name
Date
Report for Experiment
A.
Density of a metal (Show calculations)
Unknown Metal Number
1.
Mass
2.
Volume
a.
b.
3.
g
By Volume Displacement
Initial water level
ml
Final water level
ml
Volume
ml
By measurement
Height
cm
Diameter
cm
Radius
cm
Volume
cm3
Density
a.
Using Volume by Displacement
g/cm3
b.
Using Volume by Measurement
g/cm3
4
B.
Density of a salt solution (Show calculations)
1.
Salt Solution Number
Weight of cylinder
and solution in grams
Volume of Solution in mL
2.
Density from Graph (show calculations below)
g/ml
3.
Weight of the Graduated Cylinder from Graph (y-intercept)
g
4.
Weight of Graduated Cylinder from Balance
g
5.
Attach graph to report. Label axes. If you want to use a
graphing software program (e.g., Excel), attach a copy of the
print-out of the graph.
5