User's Manual

012–07192A Discover Density Set

Introduction

In this activity you are given four rectangular solid metal pieces, and four

similar plastic pieces. You are asked to take data, organize it, graph it, and

create equations relating the mass and volume of each of the two kinds of

material. A minimum of instructions are given. You should study and follow

the example titled “The Speed of Sound” which preceded this task.

Materials required

The materials needed are in compartments AB1, AB2, C1, and C2.

Procedure

1. Create a table to record the length, width, and height, volume, and mass of

the four metal pieces from compartment AB1, and a similar table for the

four gray plastic pieces from compartment AB2.

2. Record the length, width, and height in centimeters. If you are using a

metric ruler, estimate to the nearest 0.01 cm when finding these

dimensions. Use the rules regarding significant figures or other

appropriate methods of expressing uncertainty.

3. Consider the volume to be the independent variable, and the mass to be

the dependent variable when graphing the data. Prepare a graph that

shows the data for all eight objects, labeling your data points for the metal

pieces with circles, and the data points for the gray plastic pieces with

squares.

4. Draw a best-fit line for the data from the metal pieces, and another for the

data from the grey plastic pieces. If straight lines passing through the

origin do not represent the data well, recheck your measurements and

calculations for any data points that do not fit the pattern.

5. Calculate the slope of each line, and include dimensional units as part of

your calculations. Show your calculations, and use significant figures or

another appropriate expression of uncertainty.

6. Although each item had its own mass and volume, the slope of the line for

the metal pieces is constant. The metal pieces are all aluminum, and the

slope is termed the density of aluminum. Find a published value for the

density of aluminum, and compare to your value. Does your value agree

within the limits of uncertainty?

7. The gray plastic is polyvinyl chloride, or PVC. Its published density is

1.36 to 1.40 g/cm

. Does your value agree within the limits of

uncertainty?

Finding an

Equation

Relating

Mass and

Volume