U4 S2 L5 STSE Textbook Readings pages : Disposable Batteries pages : Rechargeable Batteries pages : Automobile Engines Pages 796: Industrial extraction and refining of metals Pages 798 – 801 Issues involving elecxtrochem. Textbook Practice Items page 789: items 4 and 5 page 803: items 29, 30, 31 and 32

Upon completion of this lesson, you should be able to: define primary battery, secondary battery and identify common examples of each including dry cell, alkaline, button, lead storage, and Ni-Cd compare the efficiency of burning hydrogen in a fuel cell with burning it in a combustion reaction

Batteries are galvanic cells (electrochemical cells). –They consist of two or more half-cells connected in series with two terminals. –One terminal is positive (+) while the other is negative (-). –Electrons build up at the negative terminal of the battery and flow to the positive terminal when a circuit is completed. –Typically, a circuit includes a load - something that uses the electricity like a light bulb or a motor. Two types of batteries: –primary or disposable batteries p764 cannot be recharged. It stops working when either the reducing agent or the oxidizing agent is completely consumed. Button batteries, AAA, AA, C, D …. Dry cells (cheap ones), Akaline batteries – duracell, energizer, Lithium … –secondary or rechargeable batteries. p787 Ni/Cd rechargables Car batteries – lead storage battery (lead acid battery)

Fuel Cells A fuel cell is sometimes called a flow battery

ANODECATHODE LOAD Pollution Free Electrolysis of water to make H 2 and O 2 p 802

Corrosion p 798 From hot water tanks to outboard motors to battle ships …. corrosion is a major concern! Sacrificial anode rods (oxidized metal) –Usually a piece of Zn or Mg metal. Why? Most reactive metals (lowest on the standard reduction table) The metal will protect all other metals above it on the table. In other words the lower the metal the more reactive (easier to oxidize and acts as the anode)

Cathodic protection: A DC current is passed through the object you wish to protect from oxidizing. The tank in this case is reduced – gaining mass! Creates a DC current from AC

Mining to metallurgy STSE reading / p 796 Metallurgy is the science of extracting and refining metals from ores and the compounding of metals to form alloys Native metals - occur in nature as pure metals Mineral – a naturally occurring substance that has a defined chemical composition. An ore is a rock that contains commercially viable amounts of minerals. Metals and MineralsFormulas and Names Native MetalsAg, Au, Bi, Cu, Ir, Os, Pd, Pt Carbonate Minerals CaCO 3 (calcite), CaCO 3 ● MgCO 3 (dolomite), FeCO 3 (siderite), BaCO 3 (witherite) Halide MineralsCaF 2 (fluorite), NaCl (halite) Oxide Minerals Al 2 O 3 ● 2H 2 O (bauxite), Cu 2 O (cuprite), Fe 2 O 3 (haematite), Fe 3 O 4 (magnetite) Sulfide Minerals Cu 2 S (chalcocite), CuFeS 2 (chalcopyrite), NiS (millerite), Fe 9 Ni 9 S 16 (pentlandite), FeS 2 (pyrite)

Three main steps in obtaining a pure metal from its ore. 1.Primary treatment Primary treatment is the process that concentrates the mineral. It is conducted at the mine site. (crushing, froth flotation) 2.Extracting the metal Extraction involves either pyrometallurgy or hydrometallurgy. Pyrometallurgy (or pyromet for short) involves heating an ore in a blast furnace at temperatures above 1500°C to convert the ore to a form that can be refined. Adv: Efficient, inexpensive - proven technology, readily available Disadv: pollution(CO 2 - greenhouse gas, SO 3 -acid rain!, not 100 % pure product Hydrometallurgy (or hydromet, for short) involves the use of aqueous chemicals and much lower temperatures to separate the metal from its ore. (Leaching: in situ, heap, vat) Issues: potentially hazardous chemicals used in leaching. Adv: fewer impurities, less pollution, sulfuric acid by product is marketable 3. Refining the metal Electrowinning – reduction of the dissolved metal ions by an inert anode. Electrorefining involves removing impurities in which the anode of the impure metal is oxidized and then the pure ions produced are reduced on a cathode. Issues: rerquires large amount of electricity – sources questionable!

The refining of nickel is accomplished in one of two ways. 1.Pyromet extraction (roasting) The Extracted Nickel sulfide can be refined in one of two ways: 1.Mond Process: converting Ni 3 S 2 to NiO which is refined into pure nickel by distillation (heat). Still may need to be electrorefined to remove impurities. 2.Electrolysis (Electrowinning): reducing the nickel in Ni 3 S 2 in an electrolytic cell. This is known as electrowinning. At the anode of the electrolytic cell, the Ni 3 S 2 reacts to produce Ni 2+ ions and S 8. Ni 2+ is then reduced at the cathode to produce nickel metal. 2.Hydromet extraction (dissolving) Extraction by leaching of the ore to produce a solution that contains Ni ions. (in situ, heap, vat leaching) The Ni ions are then reduced to Ni metal electrolysis (electrowinning) with an inert anode.