The discoverer of gold is unknown. • Although it is believed to have been discovered around 3000BC. • This precious metal has been highly sought after for many centuries. • Gold has the appearance of • It is soft, dense, shiny and the most malleable and ductile of all metals known. • Gold occurs as small nuggets or small grains which can be found in rocks. Metallic Yellow
Melting point: 1063 degrees Celsius • Boiling point: 2856 degrees Celsius • Density: 19.3 g cm-3 • Gold isn’t very reactive. • However, the look of its surface can be changed by chlorine, fluorine and cyanide. • Mercury can dissolve Gold, but it doesn’t react with it.
Coinage • Jewellery • Dental Work • Plating • Reflectors. • It is a good conductor of heat and electricity, and because it doesn’t tarnish when exposed to air gold can be used to make electrical conductors and printed circuit boards. • Gold is also used to help shield spacecraft and skyscrapers from the sun’s heat because it is good at reflecting infrared radiation. Uses for Gold
Other Uses of Gold Gold-198 is a radioactive isotope of gold. It is used for treating cancer. Gold sodium thiosulfate (AuNa3O6S4) is used for the treatment of arthritis. Chlorauric acid (HAuCl4) is used to preserve photographs by replacing the silver atoms present in an image.
Pure gold is referred to as ‘24 carat’ gold. It is often alloyed with silver and copper. 24 carat - 100% gold. 18 carat - 75% gold + 25% silver and/or copper. 9 carat - 37.5% gold + 62.5% silver and/or copper.
Major Steps in Extraction of Gold from its ore. Froth Flotation Host rock and specks of gold. Concentrated gold ore. Cyanide process Add zinc or electrolysis Au Au(CN)2- (aq) Extraction of Gold using Cyanide 4Au (s) + 8CN- (aq) + 2H2O (l) + O2(g) 4Au(CN)2- (aq) + 4OH- (aq) The Au(CN)2- is separated from the pulp using activated carbon. The gold is then recovered by adding zinc (metal ion displacement) or by electrolysis.
Interesting Facts • The most famous piece of gold is the face mask to the boy king of Egypt, Tutankhamun. Some of the greatest treasures of goldsmiths art was also found in his tomb.
The properties of gold give it the ability to be beaten into sheets no thicker than 0.00001 mm or 400 times thinner than a human hair. Or The fact that gold is so malleable and ductile one gram of it can be beaten into a one square metre sheet.
In every ton of seawater 1 milligram of gold has been dissolved, but at the moment it currently costs more to extract the gold from this than what the gold is worth itself. • There is about 120,000 to 140,000 tonnes of gold above ground. • Imagine a solid gold cube about the size of a tennis court. This is the amount of of gold that has been produced. • If this amount of was distributed to every person in the world, you would have only about 23 grams of gold.
History of Gold Since prehistoric times, gold has been known about and highly valued. Gold is used to symbolise purity, value and royalty. It is also a sign of wealth. Gold can be found freely in nature, however it is usually found in silver, quartz, lead, zinc or copper.