Body

Chemistry 100

Copper, Cu

areas where one could find occasional copper nugget
sometimes chunks of metal weighing pounds
rather distinctive-- reddish, shiny
mechanically distinctive-- malleable
- distorted on hammering without shattering
original uses mainly jewelry again
- sheet metal covering for wood
- light duty object-- a cup
too soft for tools-- can't hold an edge
- don't want a hammer that changes shape on impact
- don't want a knife or plow that bends easily

This is the oldest deliberate chemical technology
- older chemical technolgy?: fire, cooking, fermenting, pottery
- transforming one substance into another
- by deliberate action
Copper ores-- usually colored blue, green, some are black
- used a pigments previously (turquoise, malachite)
- easily located and identified
If placed near hot carbon (charcoal)
- change into the metal
- chemists say we reduce the compounds
  - CuO (black powder) + C (black charcoal)
  - heat
- get bright red metal
- sometimes as a sponge like substance
- sometimes as little metal droplets

Whoever discovered this

found it was repeatable
was able to identify right ores (minerals, rocks)
found enough material to promise useful products
found slightly better ways to make and confine the fire
became a metallurgist
a skilled craftsman (probably holder of a secret)
- evidence that some sold out to other countries
- technolgy spread much faster than normal migration of peoples

Also discovered that a pottery form in bottom of fire

But copper, like gold, is too soft for most uses and this early copper technology still wan't all that important. But...

Sometimes the copper was contaminated
- some ores produced "better" metal (accidental alloys)
Deliberate additions also produced better metals
These are alloys
- Bronze-- usually add Tin
  - Sometimes Arsenic, antimony, Lead
- (Julius Caesar invaded and occupied Britain around 400 BC
- why? Partly to gain control of Tin mines in Cornwall)
- Copper and Zinc (later discovery) = Brass

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reddish metal (one of the very few metals that's not silver color)
moderately inert (too reactive and it's less useful)
patina-- as copper weathers, it is coated with copper salts
- characteristic blue color
- mostly tough and weatherproof-- slows further corrosion
- so copper often lasts a long time
Copper roofs (often too expensive now)
Copper plumbing pipes (replaced with cheaper plastic pipe)
Bronze statues
Bronze Cannons (1000-1800 AD)
Electrical Wiring (no alternative metal)
Cooking Pots (good heat conductor)
coinage (even US penny is now mostly cheaper Zinc)

Most copper is used as the metal or in copper alloys; there are very few uses for copper compounds

One important ore is the sulfide CuS
- roasted in air 2 CuS + O₂ -->2 SO₂ + 2 CuO
- reduce oxide to metal 2 CuO + C ---> 2 Cu + CO₂
- copper smelters, historically, major source of SO₂

Here are some links to a number of other Copper Web Sites you might visit