 |
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 |
|
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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 |
|
|
|
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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 |
|
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| 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. |
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