The Physics Factbook
Edited by Glenn Elert -- Written by his students
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|Brown, Theodore L. and Lemay Jr., H. Eugene, Chemistry: The Central Science. Prentice Hall Inc, Englewood, New Jersey, 1985: 10.||Table 1.4: Densities of Some Selected Substances
Density (g/cm3): 19.32
|World Book Encyclopedia. United States, 1996: 249.||Properties of Gold:
Gold (Au): Density (at 20 degrees Celsius) 19.32 g/ cm3
Gold weighs about 19 times as much as an equal volume of water at 20 degrees Celsius."
|Santine, Arthur. Gold Jewelry. 5 January 2006.||"When weighing gold it is the 'density' that is measured. Gold has a much higher density compared to many of the metals used to alloy with it to create varying karats and colours of gold jewelry. The density of gold is 10.18 troy ounces/in3 of pure gold."||19.32 g/cm3|
|Gibbs, F.W. William Lewis and Platina; Bicentary of the 'Commercium Philosophicotechnicum' [pdf]. Platinum Metals Review. Vol. 7, No. 2 (1963): 66–69.||"Lewis's platina was still not pure, as he reported an average density of about 17; whereas that of an alloy of equal parts of gold and platina was about 16.5. Thus, density measurements were not of very great help."||16.5 g/cm3
|Greenwood, Barbara. Gold Rush Fever; A Story of the Klondike, 1898. Ontario: Kids Can Press, 2001.||"Since gold is 19.3 times heavier than water, it sinks to the bottom."||19.3 g/cm3|
For thousands of years, people have mined gold. The desire for gold has flowed in the blood of all cultures, just as it flows in the veins of the mountains of all continents. People have adorned their dead in gold, used gold to create money and they have used gold in medicine to kill certain types of cancer. Through the ages people have lived and died for gold. The stampede for gold searched in a frenzy for it, from South Africa to the Australian outback, from California to the Klondike.
Gold is one of the most desired metals because of its strong physical and chemical properties. Gold has the greatest ductility of all metals, considering 30 grams can be drawn into a wire that is 80 kilometers long without breaking. Also being the most malleable, it is one of the most versatile of all the metals. Gold can be hammered into different shapes for currency or jewelry. Gold is a good conductor of heat and electricity, and does not rust like iron when exposed to water or oxygen.
One of gold's most important properties happens to be its density. Density is the amount of mass in a unit volume of that substance. In simpler terms,
density [grams/cm3] = mass [grams] / volume [cm3]
To date, the recorded density of gold is 19.32 grams/cm3. Gold weighs approximately 19 times as much as an equal volume of water. Back in the day of the gold rush, the density of gold played an important role in the panning process. A poor man, searching for gold that would be hiding in the gravel near creeks and streams, could take a frying pan, scoop up gravel and sand near the river bed, and swirl it. The gravel and sand would wash out, and the remaining solids would separate and the heaviest would sink to the bottom of the pan. This is an example of the density of gold at work. Gold, being denser than the other solids as well as the water, would sink to the bottom of the pan. After the water and gravel is poured out, the thin traces of gold would remain. The golden metallic luster, even though exposed to oxygen in the air and water, could be seen by the naked eye. To sum it up, the density of this valuable metal eliminated the need for fancy equipment.
Gold, the most sought after metal throughout the ages, would not have been discovered if not for its density. Are you worth your weight in gold?
Alex Scelso -- 2008
|Cutnell, John D. and Kenneth W. Johnson. Physics 4th Edition. New York: Wiley. 1998: 308.||
|CRC Handbook of Chemistry & Physics. 55th ed. Ohio: Chemical Rubber Co. 1974-75: B-15.||"b.p 2807C; sp. gr. 19.32 (20C); valence 1 or 3. Known and highly valued from earliest times."||19,320 kg/m3|
|Huber, Carol. Gold Panning. Chugach National Forest. 1997.||"Gold has a specific gravity of 19.3, meaning it is more than 19 times heavier than an equal volume of water."||19,300 kg/m3|
|The Illustrated Science and Invention Encyclopedia. Connecticut. H.S. Stutmann, 1974.||"Its tarnish-free surface, attractive colour and very high density -- one cubic foot (0.028m3) weighs over half a ton -- as well as its rarity, make it highly prized."||18,000 kg/m3|
|The Educators Resource Guide to the Klondike Gold Rush of 1898. Klondike Gold Rush National Historical Park. Seattle, Washington.||"Gold is an extremely dense mineral with a specific gravity of 19.2 (19.2 times heavier than water)."||19,200 kg/m3|
Gold is a precious metal which has been sought after by humans ever since they had the concept of possession. People of almost every culture have a history of alchemy, the superstitious process of turning rocks or cheap metals into gold. Alchemy has been recorded to have been practiced as far back as 1900 BC by the Greek-named Egyptian King Hermes Trismegistus. The Density of gold is first known to have been investigated by Archimedes circa 210 BC in the famous story of where the King of Syracuse asked Archimedes to find out if his crown was made of real gold. Archimedes determined this by submerging the crown and a piece of gold with the same weight in water and observing how much water was displaced.
This led to the definition of density, Density"="mass/volume. As found through that equation, the density of gold is 19,300 kg/m3.
The standard units for density are kg/m3 but density can also be recorded as specific gravity which is the density of the material divided by the density of water (1000 kg/m3). Specific gravity of gold (then recorded as 19.2) was important to the gold miners of the mid-1800s for when they needed to determine whether they had gold or fool's gold since they did not have any quality measuring devices. The high density of gold also allowed a common form of gold accumulation called panning. This was where gold-carrying water was taken into the pan and shaken. The less dense sediments would float to the top and the very dense gold dust would sink to the bottom where it could be collected. Even though this was a slow means of getting gold and was impractical to do year-round in places like Klondike where the water was frozen nine months per year, panning to step one for prospectors when deciding where to stake a claim.
Ruwan Meepagala -- 2004
|Cutnell, John D.& Johnson, Kenneth W. Physics 4th Edition.New York: Wiley, 1998: 308.||
|World Book Encyclopedia G. Chicago: World Book, 1993: 249.||"It's density is 19.32 grams per cubic centimeter at 20 °C.||19.32 g/cm3|
|Strauss, Mike The Gold Rush of 1849. 2003.||"Scientifically speaking, gold has a very large density, about 19.3 gcm-3."||19.3 g/cm3|
|Smiths, Alphers W. Elements of Physics, 5th Edition. City: McGraw Hill, 1948: 719.||
|Goldslinger. Gold Data Facts Page. 2002.||"Gold 15.6-19.4"||15.6–19.4 g/cm3|
Gold has been considered a commodity and very valuable for many years. Its attractiveness and physical qualities add to its value. Gold is also very soft making it easy to work with.
Density is equivalent to the mass per unit volume with the given equation:
ρ = m / V
It is commonly measured in kilograms per meter or grams per cubic centimeter.
The importance of the density of gold dates all the way back to the mid 1800s during the gold rush. Various mining techniques were developed by gold miners to search for gold in the bottom of rivers, lakes, and oceans. Panning was the most common form of gold mining because anybody could do it. Miners would swirl sand from the water in a pan until the gold flakes were separated from other sediments it was attached to. The gold flakes would fall to the bottom of the pan in the water. It was relatively easy for a miner to determine whether he had found gold or not. A miner would take a questionable piece of gold along with a piece of real gold and drop it in his pan filled with water. The real gold would fall to the bottom of the pan before the questionable piece of gold, commonly iron pyrite (fool's gold).
Gafei Szeto -- 2004
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