An old riddle asks “Which is heavier, a pound of feathers or a pound of lead?” The answer is obvious, of course, since a pound of feathers and a pound of lead both weigh the same, one pound. However, there is clearly something different about a small piece of lead and a large bag of feathers, even though they weigh the same. What is this difference?

The relationship between the lead and feathers is expressed by the physical property called density. Density is defined as the ratio of a substance’s mass to the volume it occupies.

Density (g/mL) = Mass (g)___ Volume (mL)

In this laboratory exercise, you will be using skills and techniques learned earlier to determine the identity of different substances. To determine the precision of your technique, you will calculate the percent error, which is a comparison of the differences between the measured value and accepted value. Percent error can be determined as follows:

% Error = (Measured Value – Accepted Value( x 100 Accepted Value

OBJECTIVES

When you have completed this activity, you should be able to:

Observe the chemical and physical properties of substances to interpret the structure of and the changes in matter.

MATERIALS

Balance Rectangular solid

Metric ruler Metal cylinder

100 mL graduated cylinder 250 mL beaker

PROCEDURE

PART I: RECTANGULAR SOLID

Mass:

Use the balance to determine the mass of the rectangular solid.

Record the mass to the nearest 0.01 g in the data table.

Volume:

Use the metric ruler to measure the length, width, and height of the rectangular solid.

Record these measurements to the nearest 0.1 cm in the data table.

Calculate the volume using the following formula:

Volume (cm3) = length (cm) x width (cm) x height (cm)

Record the volume in your