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Environmental Education Homepage |
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Make a list of the unique physical properties
of gold. (Gold is highly malleable, highly reflective, and an
excellent conductor. It is also ductile; that is, it can be hammered
out into wire or threads. Gold does not rust, tarnish or corrode, nor
does it dissolve in water or most acids.)Based on library research, identify as many
uses for gold as possible. Relate each one to gold's physical
properties.As early as A.D. 100, alchemists tried to mix
one substance with another to produce gold. Why did they fail?
(Gold is a pure substance, one of the 109 elements known to
science, and thus could not be the result of a mixture.)Gold is a metal. What properties does it share
with other metals? (Like all metals, gold is shiny, a conductor of
heat and electricity, and can be hammered without breaking.)
Make a kit to conduct tests and prepare charts
comparing metals. Use copper wire, tin cans, iron nails, and lead
fishing weights. Test hardness by scratching each metal with a file,
then categorize each one as "very soft," "soft," "somewhat hard," or
"very hard." Note the color, shine, and flexibility of each sample.
Silver conducts electricity better than gold
and costs less. Why, then, is gold used to plate electrical contacts
in high-quality switches and in computers? (Silver tarnishes when
it combines with impurities in the air and loses its
conductivity.)Illustrate the properties of malleability and
ductility. Collect such items as clay, putty, pastry dough, cheese,
kneaded erasers, marshmallows, aluminum foil, and taffy and ask
students to manipulate them, then to order them from most to least
malleable, and from most to least ductile.Discuss the difference 18K and 24K of gold.
Have student clip jewelry advertisements from the newspaper, noting
the different karat values and prices. (A karat is a unit of
fitness for gold equal to 1/24 part pure gold in an alloy; thus 24K
denotes pure gold, whereas 18K indicates a mixture of 18 parts gold
and 6 parts other metals.)Speculate why jewelers would prefer to work
with an alloy of copper and gold rather than either gold or copper
alone. (Pure gold is a soft metal that scratches, bends and breaks
easily. Jewelry made from it would not last very long. Copper, on the
other hand, is an inexpensive, harder metal that dulls rapidly and
turns green when exposed to air. When copper and gold are melted
together, the alloy formed is sturdier than the pure metals and has
most of the brilliance of gold.)
Gold is a mineral. What does that mean? (A
mineral is something found in nature that is neither a plant nor an
animal. Most rock contain two or more minerals.)Gold is also a metal. Are all minerals also
metals? Are all metals also minerals? (All metals are not
minerals. For example the metal bronze is not a mineral- it is not
found in nature. Most minerals are nonmetallic. Graphite, gypsum, and
halite are all nonmetallic minerals.) In nature, gold is usually found in
combinations with other minerals or metals, such as silver or copper.
Once the ore is mined, the gold must be separated from other
substances. Ask students to brainstorm ways of separating substances.
Discuss or experiment with the following methods. Separate a mixture
of sand and water by using a coffee filter; separate a mixture of
sand and sugar by adding water to dissolve the sugar, then pouring
the mixture through a filter, leaving only the sand behind; separate
a mixture of iron powder and sulfur powder by using a magnet; and
separate salt from salt water by allowing the water to evaporate,
leaving the salt.Show "Out of the Rock," a 28 minute videotape
about minerals (available on a free-loan basis from the
Audiovisual Library, U.S. Bureau of Mines. Cochrans Mill Road, P.O.
Box 18070, Pittsburgh, PA 15236.)Invite a jeweler with goldsmithhing experience
to demonstrate the craft. For a listing of goldsmiths in your area,
write to Manufacturing Jewelers and Silversmiths of America, Member
Services, 100 India St., Providence, RI 02903; telephone
800-444-6572.Discuss the use of gold as a monetary
standard. During the early part of this century, most countries were
on "the gold standard." This meant that a specified amount of the
national currency could be exchanged for a stated amount of gold from
the national treasury. In the U.S. during this period, each paper
dollar had a value of 25.8 grains (1.67 grams) of gold held in the
national treasury. In 1934, the U.S. went off the gold standard to
limit private citizens' access to gold, giving the federal government
greater influence over the economy. Our legal tender is now backed by
the U.S. Government's promise to pay.Check the newspaper for current gold prices
and make bar charts to show how prices fluctuate over time. Discuss
the factors that affect prices and the implications of price
fluctuations for jewelers and other gold buyers.
