 Density - a Physical Property Physical Properties Elmhurst College Diet vs. Reg. Coke Density of Ice Density of Gold Chemistry Department Density of Liquids Density of Gases Virtual ChemBook Do the movies depict the weight of gold bars accurately?

 How heavy is a gold bar? In the movies, how easily do they show someone handling a bar of gold? Should you be able to pick it up easily? How many gold bars do you think you can carry? In this exercise, you will calculate the weight in pounds of a gold bar.

 Densities of Common Elements and Compounds Substance Density grams per mL or cc Water 1.00 Aluminum, Al 2.70 Iron, Fe 7.80 Gold, Au 19.30 Mercury, Hg 13.5

Mathematical Definition of Density

The formal definition of density is mass per unit volume. Usually the density is expressed in grams per mL or cc. Mathematically a "per" statement is translated as a division. cc is a cubic centimeter and is equal to a mL Therefore,

 Density = mass = g/mL volume

Example: How heavy in pounds is a gold bar pictured on the right. The dimensions of gold bars held in Federal Reserve Banks is:

7 x 3.625 x 1.75 inches

Solution:
First, convert the measurements in centimeters.

1 inch = 2.54 cm

 7 inches x 2.54 cm = 17.78 cm 1 inch

Similarly, 3.625 in = 9.21 cm;
1.75 in = 4.45 cm

Find the volume of the gold bars in cubic centimeters  Volume =
17.76 cm x 9.21 cm x 4.45 cm = 727.9 cc

Calculate the weight of the gold bar using the density of gold, which is: 19.3 g/cc

Use the density as a conversion factor:

19.3 g = 1 cc

 727.9 cc x 19.3 g = 14,048 g 1 cc

Convert from grams to pounds.

1 lb = 454 g

 14,048 g x 1 lb = 30.94 lb 454 g

So the next time you see gold bars in the movies, look to see how easily they appear to pick them up. Thirty pounds is a good amount of weight that is not casually picked up.